Efficacy of an anoestrous treatment for dairy cows is reduced if administered within 3 weeks of calving. - Nation DP; Macmillan KL; Taufa VK (Proceedings of the New Zealand Society of Animal Production, 1997)
The effect of treating dairy cows with anovulatory anoestrus (n=660) at various intervals post-partum was investigated. Treatment consisted of priming with progesterone using an intravaginal device (CIDR-B) for 6 days, with an injection of oestradiol benzoate 24h after device removal. The mean interval from treatment termination to conception tended to be greater for cows calved less than 3 weeks at diagnosis than contemporaries calved at least 3 weeks (32.8 6.3 vs 23.7 ± 1.1 days; p<0.1). Final empty rate was higher for cows diagnosed and treated within 3 weeks post-partum (39% vs 13%; p<0.001). Survival analysis accounted for the higher empty rate to determine the probability of pregnancy over time. Cows calved less than 3 weeks at treatment had a lower probability of pregnancy than contemporaries calved at least 3 weeks (p<0.01). This study found a negative effect of treating anoestrous cows within 3 weeks post-partum. Further work should define the nature of this problem and the value of delaying treatment until at least 3 weeks after calving.

The ethically improved sheep concept. - Scobie DR; Bray AR; O'Connell D (Proceedings of the New Zealand Society of Animal Production, 1997)
The need to improve animal welfare and reduce chemical residues to maintain the competitive position of our sheep products is unquestionable. However sheep producers perceive that the required actions are in conflict with production, so there have been few recent changes which allay consumer concerns. This paper discusses possibilities for producing more attractive products without substantial reductions in production or increases in costs. It identifies gene pools that should be exploited to develop a polled sheep with a short tail, that is devoid of wool on the head, legs, belly and breech. It reviews evidence that shows such animals require less handling and chemical treatment, and produce more lambs. It is proposed that these traits be accumulated into "Ethically Improved Sheep". The concept of ethically improved sheep is not presented as a prescribed combination of breeds. There are a number of breed sources of each trait, and other traits should be introduced as they become available or important in the future. This would permanently reduce the need for husbandry practices that emulate the same effects, thus reducing input costs, pre-empting any bans and forestalling any trade barriers based on current husbandry practices.

Evaluation of a vaccine to control bull behaviour - Jago JG; Bass JJ; Matthews LR (Proceedings of the New Zealand Society of Animal Production, 1997)
To determine the effect of Vaxstrate®, an anti-GnRH vaccine, on the development of bull behaviour, 90 Friesian bull calves were either castrated at 2 months of age (steers, S), immunised against GnRH at 2, 2.5, 4 and 7.5 months of age (immunocastrates, I2), at 4, 4.5 and 7.5 months of age (I4), at 7.5 and 8 months of age (I7.5), or left intact (bulls, B). Immunocastration delayed the prepubertal increase in testosterone. There were no differences in behaviour between immunocastration treatments. Mounting behaviour and paddock damage for immunocastrates and steers were lower than for bulls until 13 months of age, after which there was no difference between immunocastrates and bulls, and both were higher than steers. Bulls had a higher frequency of agonistic behaviour than both immunocastrates and steers; there was no difference between immunocastrates and steers until 16 months of age, when immunocastrates scored higher than steers. Immunisation against GnRH before puberty temporarily delayed the development of sexual and agonistic behaviour of young bulls and could provide a practical alternative to traditional methods used to control bull behaviour.

Evaluation of different staining techniques for determination of membrane status in spermatozoa. - Smith JF; Murray GR (Proceedings of the New Zealand Society of Animal Production, 1997)
Changes in the composition and integrity of spermatozoal membranes occur both during the normal capacitation and acrosomal reactions involved in the fertilization processes and as a result of different handling and storage procedures. Techniques to monitor these changes are essential to any study on methods of sperm preservation and such techniques should be both accurate, simple and rapid to apply. A series of tests were conducted to evaluate a range of staining techniques to measure the integrity of the sperm plasma membrane (permeable membrane indicates non-viable sperm) and to measure the status of the acrosomal membrane (indication of capacitation and acrosomal reaction). The possibility of a combination of stains to provide simultaneous answers to both parameters was also attempted. Semen both fresh and frozen from both rams and bulls was used. The stains evaluated were: Nigrosin-Eosin (NE), Nigrosin-Eosin- Giemsa (NEG), Hoechst 33258 vital stain as both wet and dry mounts, Carboxyfluorescein and Propidium Iodide (CF-PI), SYBR-14 and Propidium Iodide (SYBR-PI), Pisum sativum -fluorescein isothiocynate (PSA-FITC), Chlortetracycline (CTC) and a FITC- labelled monoclonal-antibody (Mab) to an acrosomal protein. The techniques were graded for their accuracy, ease of use, equipment requirements and also for repeatability or adaptability to spermatozoa in different media. No single or combination of techniques proved suitable for both plasma and acrosomal membranes and most techniques varied in their suitability for different semen preparations.

Expected pregnancy rate in recipient cattle, sheep and goats derived using a model incorporating embryo and maternal contributions to embryo survival - McMillan WH (Proceedings of the New Zealand Society of Animal Production, 1997)
Pregnancy rate to term after embryo transfer (ET) in cattle ranges from 30-50%. A model is proposed which partitions embryo survival into independent and binomial embryo and maternal components. Parameters for these two components can be used to calculate expected pregnancy rates. In 35 out of 36 sets of data in which pregnancy data were recorded following contemporary single and twin ET, or single and twin ovulation, expected pregnancy rate was either within 5 percentage units or one standard deviation of observed pregnancy rate. Pregnancy rate changes in single ET recipients or single ovulating females are equally sensitive to changes in the embryo and maternal components. In contrast, pregnancy rate changes in twin ET recipients or twin ovulating females are more sensitive to changes in the maternal component. In conclusion, these data suggest that the model adequately describes embryo survival and pregnancy rates. Accordingly, research to improve the maternal component seems warranted in order to improve reproductive success.

Farmer groups, a measure of their effectiveness - Webby RW; Paine MS (Proceedings of the New Zealand Society of Animal Production, 1997)
From 1993 to 1995 changes in sheep and beef cattle farmer learning styles; their beliefs about group interactions and their beliefs about the farm system were measured in three groups located in the upper North Island. The groups were each part of a group farm monitoring programme involving scientists from the Whatawhata Research Centre. Using a survey questionnaire, the study sought to identify ways of improving the delivery of technology to group members. Most group members expressed a preference for logical learning experiences (50% of those surveyed) followed by problem solving (32%), action (12.5%), and social interaction (5.5%). Belief maps which illustrate group interactions identified problems in group cohesion. Farm system belief maps identified distinct categories of farm system components, viz.: performance related technologies; relatively non-complex technologies; relatively complex technologies. Over time, beliefs about stock policies became more closely related to farm performance indicators such as profit.

Finding QTL's without markers: experience with FINDGENE. - McEwan JC; Morris CA; Bisset SA; Kerr RJ (Proceedings of the New Zealand Society of Animal Production, 1997)
FlNDGENE is a mixed inheritance model computer program which can analyse extensive animal pedigrees. It partitions the observed variance into fixed effects. polygenic inheritance, a two allele major locus effect and a residual envimnmental variance. It do-es not require genotype information. Data from three New Zealand sheep experiments where faecal nematode egg count (FEC) information had been collected were examined by this method. They included a long term selection experiment for FEC in Rornneys at Wallaceville, another in Perendales at Ruakura, and a randomly mated Coopworth flock at Woodlands Research Station. All PEC traits were initially transformed using the function log.(x+lOO). The final model included the effect of sex/year contemporary group, birthday and polygenic inheritance in addition to a 2 allele Mendelian gene effect. Results from all three data sets suggested a dominant a’utosomal gene for host susceptibility was affecting strongyle PEC values in the summer/autumn period with estimates of 0.37,0.69 and 0.72 log eggs/g for the single allele effect from Romney, Perendale and Coopworth flocks respectively. Corresponding values for dominance were 0.47,0.44 and 0.88 log eggs/g with susceptible allele frequency 0.14.0.55 and 0.69. When considered together, these results suggest that at least one QTL is affecting the development of host resistance to internal parasites in young sheep. The identification and characterisation of this QTL may result in useful novel methods of internal parasite control.

Free and conjugated levels of zearalenone in ewes mated on grass dominant pasture or chicory. - Kramer R; Keogh RG; Sprosen JM; McDonald MF (Proceedings of the New Zealand Society of Animal Production, 1997)
Zearalenone is an oestrogenic mycotoxin commonly found in New Zealand pastures (di Menna, and et al., 1987). Ingestion of zearalenone by sheep causes reductions in reproductive performance (Smith, and et al.,1990). It is likely that high zearalenone concentrations in pasture around mating will often be sufficient to affect reproductive per-formance of the ewe. Chicory pastures contain very low zearalenone concentrations and therefore have potential as a feed for ewes prior to and during mating. The aim of this trial was to determine the levels of free and conjugated zearalenone in the blood and urine of ewes grazed on either grass-dominant pasture or chicory prior to and during the mating period, and assess any subsequent effects on reproductive performance.

Genetic analysis of meat quality in cattle. - Kappes SW; Stone RT; Smith TPL; Keele JW (Proceedings of the New Zealand Society of Animal Production, 1997)
Geneticlinkagemapsenablescientists toidentify regionsofthegenome thatinfluenceproduction related traits. Sufficientnumber of polymorphic markers (5 1800) are available for a genome-wide quantitative trait loci (QTL) search and subsequent use of markers forselection.Selectionforcarcass traitshasbeen limitedb-xausecurrent marketsystemsdonotprovidecarcass information to thecattle producer. Information obtained from mapping studies will allow producers to select for carcass traits and other traits that are difficult and expensive to measure in production settings. Mapping information will also be used to identify the molecular mechanisms controlling the genetic component of carcass traits and other quantitative traits.

Genetic studies of bloat susceptibility in cattle. - Morris CW; Cullen NG (Proceedings of the New Zealand Society of Animal Production, 1997)
Bloat costs the dairy industry about $50 million per year and one of the possible long- term solutions is to breed cattle for reduced susceptibility. Studies on two herds established at Ruakura in 1972/73, and selected divergently for high susceptibility (HS) or low susceptibility (LS) to bloat, have shown that: (1) bloat score on any single day of serious challenge has a heritability of 0.19±0.04; (2) the within-animal repeatability of scores across days is 0.44±0.02; (3) divergence of bloat score between herds has now reached 2.4 genetic standard deviations; (4) the recent response rate in the HS herd has been approximately linear whilst the LS response has plateaued; (5) 75% of the HS herd and 2% of the LS herd are at risk of death from bloat if left untreated. Alternative definitions of the bloat syndrome have been investigated; one of these (maximal bloat score) has a heritability of 0.30±0.06. Using this definition, a mixed-inheritance segregation analysis was undertaken, which led us to the conclusion that a major gene for susceptibility was segregating as an autosomal recessive. The implication is that the use of non-carrier AI sires in industry could minimise the bloat problem in one generation, by avoiding production of all homozygous double-recessive progeny.

Gestation length in Pere David's and red deer hybrids - Goosen GJ; Fennessy PF; Pearse AJ; McEwan KM (Proceedings of the New Zealand Society of Animal Production, 1997)
Père David`s deer (PD) have a 49 day longer gestation than red deer (283.4 ± 6.1 (SD) and 234.4 ± 3.4 days). In F1 hybrids (PD sire), male progeny had a longer gestation than females (268.8 ± 6.4, n=10 and 262.0 ± 4.5, n=10, P<0.01), both greater than the mid-parent mean of 259 days. The male and female progeny of F1 sires and red dams had a gestation length of 249 ± 5.5 (n=275). Segregation analysis suggests two normal distributions with a difference in means of 7 days. In the reverse hybrid (F1 dams), the gestation length of 242.5 ± 3.3 days (n=19) was significantly shorter than the backcross hybrid progeny of F1 stags. The control of gestation length in PD hybrids is clearly very complex although we have found evidence of two linked markers which individually account for 2.4 and 2.7 days of the difference in gestation length.

Growing wool in tissue culture - which sheep breed is best? - Winder LM; Scobie DR; Bickerstaffe R (Proceedings of the New Zealand Society of Animal Production, 1997)
Individual wool follicles were isolated from adult sheep and maintained in tissue culture for three days. Follicles from Merino, Poll Dorset and Suffolk animals were classified as fine wool types and were compared with follicles from Romney, English Leicester and Drysdale animals which were termed a coarser wool type. There were significant differences in both follicle survival and the rate of fibre growth between coarse and fine follicle types maintained in vitro. Only 48% of follicles from animals with fine fibre types survived in tissue culture. In contrast, 84% of follicles from coarse fibre types remained viable in vitro (P<0.01). The fibre growth rates of viable follicles was also significantly different between fibre types (P<0.01). Follicles isolated from animals classified as fine fibre types had a fibre growth rate of 108 ± 16um per day compared with 170 ± 12um per day fibre growth by animals with coarser fibre types. In vitro fibre growth by animals with large, straight follicles such as those from the English Leicester and Drysdale animals was greatest and a high proportion remained viable. Furthermore, follicles from these animals were easy to isolate relative to finer fibre types. Dissection of finer follicles was considerably more difficult, due to the decreased follicle size, curvature and high follicle density; factors which may be responsible for their reduced viability in vitro.

Growth and onset of puberty in two genetically different lines of Holstein-Friesian cows, selected for either heavy or light body weight - Garcia-Muniz JG; Holmes CW; Wickham BW (Proceedings of the New Zealand Society of Animal Production, 1997)
Heavier body weight affects dairy farm profitability through its effects on extra dietary energy requirements for maintenance and growth and on extra income from culled cattle; therefore it is now included in the new Animal Evaluation System used with New Zealand dairy cattle. The selection of two lines of Holstein-Friesian cattle began in 1989 using proven sires with either high (H) or low (L) estimated breeding value (EBV) for live weight (LW), but which were all of high genetic merit for milk solids yield. This paper reports on the onset of puberty and the pattern of growth from birth to first calving of heifers from these two genetic lines of cattle.

Growth of friesian calves offered three allowances of milk replacer. - MacDonald KA; Penno JW (Proceedings of the New Zealand Society of Animal Production, 1997)
Milk and milk products are a more expensive source of dietary nutrients than pasture and cereal based supplements. Therefore restricting milk intake could reduce the cost of rearing replacement cattle. Friesian calves (n=60) were allocated to three balanced treatment groups receiving a High (29.8 kg), Medium (21.8 kg) or Low (16.6 kg) allowance of milk replacer (MR). Calves offered the Low allowance were weaned from MR at day 42, while the other two groups were weaned from MR at day 49 of the trial. Calves were weighed at days 0, 49, 70 and 119 following a 12 hour fast. The liveweight gain of the High group was greater (P<0.05) during days 0-49 and 49-119 than the Medium and Low groups. The calves on the Medium and Low MR allowance were 3 kg lighter on day 49 and 7 kg lighter on day 119 than those of the High MR allowance. Differences in growth rates between treatment groups prior to day 49 were smaller than would be expected from the large difference in metabolisable energy intake from MR. Furthermore, reducing MR allowance did not increase meal intake as was expected. It is likely that the calves partially compensated for a lower MR intake by increasing pasture dry matter intake. When choosing to restrict the level of nutrition offered to the young calf, the effect on animal performance both before and after weaning must be recognised.

Heritability of resistance to flystrike in New Zealand Perendale sheep - Brandsma JH; Blair HT (Proceedings of the New Zealand Society of Animal Production, 1997)
The cost of fly strike to sheep farmers is considerable. Apart from animal deaths, other costs include: labour and chemicals for control, reduced wool value and poorer animal performance. Also, there is a cost in animal suffering and potential for chemical contamination of wool. Furthermore, fly resistance to currently available forms of chemical control is increasing. A complementary approach to controlling fly strike is to enhance the animal’s genetic resistance via selection.

The impact of turnips on dairy production as evaluated by component trials, simulation modelling and farm systems research. - Thomson NA (Proceedings of the New Zealand Society of Animal Production, 1997)
A comparison of different methods (component trials, systems modelling and whole farm trials) for evaluating dairy farm inputs is made using the example of turnips grown on-farm as a summer forage. Component studies conducted at the Taranaki Agricultural Research Station and at DRC showed respectively increased (P<0.01) milksolids production of 36 and 66 g milksolids (MS)/kg turnip DM. Modelling the use of turnips using a farm management model (UDDER) has shown the practice to be profitable in a dry year if the crop exceeds 8.0 tonne DM/ha and in a normal year, 10.0 tonne DM/ha. A programme designed to demonstrate the value of turnips on summer milksolids production (More Summer Milk) showed on 3 farms over 2 years a decrease of 16 kg MS/ha. The sowing of 7-9% of the farm into turnips (DM yields varied from 6.5 - 11.5 tonne DM/ha) resulted in less pasture conserved (180 kg DM/ha) and, by the commencement of feeding turnips; reduced milksolids production (0.2 kg/ha/day), lower average pasture cover (360 kg DM/ha) and lower cow condition score (0.2 units/cow). Feeding turnips resulted in a small increase in milksolids production, insufficient to compensate for the initial production loss. UDDER simulated the farm situation prior to feeding turnips reasonably well but the response to turnip feeding was higher than occurred on-farm. The results highlight that the impact of a forage crop on dairy production cannot be predicted from short-term feeding trials or currently available farm systems models.

Incorporating turnips into the pasture diet of lactating dairy cows. - McFerran R; Singh V; Parker WJ; Morris ST (Proceedings of the New Zealand Society of Animal Production, 1997)
Turnips have become a popular forage crop in New Zealand and Australia for supplementing dairy cows grazing pasture during the summer and autumn. However, it is unclear what combination of turnips and summer pasture best meets the dietary requirements of lactating dairy cows. New information was therefore gathered on the digestibility of turnips fed in conjunction with summer pasture and this was used in the ration balancing model, SPARTAN, to determine the optimum combination of turnips and summer pasture for a `large` dairy cow (500 kg, 17 l/d) during mid-to late-lactation. Twelve wethers (n = 3/group) were used to determine the in vivo digestibility of four diets with a summer pasture (P):turnip (T) dry matter (DM) ratio of: 100P:0T, 75P:25T, 50P:50T and 0P:100T. The DM digestibilities of the diets, fed at 1.0 kg DM/d, were 65, 71, 81 and 89%, respectively. As the portion of turnips in the diet increased so too did the dry matter intake (0.64, 0.78, 0.77 and 0.93 kg DM/d, respectively). Relative to pasture, turnip was low in fibre and crude protein but high in available carbohydrate. The optimum portion of turnips, on a DM basis, when fed in conjunction with summer pasture was 21% of the dietary intake. For the average New Zealand dairy cow, this equates to 3-5 kg turnip DM/d. A 100% turnip diet would not meet cow requirements because of the low fibre and protein content of turnips, but a 100% pasture diet could, providing it was reasonable of quality (ca. 65% DMD and at least 17% crude protein) and available in sufficient quantity not to restrict cow intake.

An Index to assist multiple trait selection of terminal beef sires in the UK - Amer P; Simm G (Proceedings of the New Zealand Society of Animal Production, 1997)
A selection index with the objective of achieving economic improvements in saleable meat yield, calving ease and feed intake has been used in the UK beef industry since the mid 1980`s. In this paper, an improved index, which incorporates estimated breeding values for traits currently recorded in UK pedigree beef cattle, is described. The recorded traits are taken as birth weight, calving ease, gestation length, 400 day weight, ultrasonic fat and muscle depths, and muscling care. The breeding objective is made up of commercial carcass traits, calving ease and gestation length and is directed exclusively towards terminal sire buyers. When all available traits have been recorded in pedigree beef cattle herds, calving traits (birth weight, gestation length and calving ease) explain approximately 30% of the variability in index scores, with the remainder explained by the growth and carcass traits. The expected economic superiority of progeny from the top 40% of bulls ranked on the index, over the average bull, is £2.48 for carcass weight, £.79 for carcass conformation score, £-.05 for carcass fat score, £.37 for gestation length and £.24 for calving case. The overall economic superiority of progeny from the top 40% of bulls (£3.82 is reduced by 17% if both ease and gestation length are not recorded and by 10% if ultrasonic scanning traits are not recorded. Two component indices (for calving and production trait groups respectively) are also proposed to allow commercial bull and semen buyers to adjust emphasis on the two groups of traits depending on their individual production circumstances. In conclusion, the new index incorporates new selection criteria, and a more rigorously defined and transparent breeding objective which should maximise future benefits from performance recording and Best Linear Unbiased Prediction (BLUP) genetic evaluations in UK beef cattle.

Induction of Parturition in Dairy Cows - A Survey from spring 1996 in the Waikato region. - Verkerk GA; Goble G; McDougall S; Woods M; Clark B; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 1997)
Data were gathered relating to the practice of induction of premature parturition from farms in the central Waikato during spring 1996. A standard two-injection glucocorticoid treatment regime was employed. The reproductive tract of each cow receiving this treatment was examined 3 - 5 days post partum. Additional information relating to cow management was collected by interviewing participating herd-owners. Preliminary data relating to subsequent reproductive performance of a subset of the cows are also presented. Accurate data were obtained for a total of 691 cows on 31 dairy farms. The mean induction rate was 10% (range 2 - 24%) of the cows in each herd. The distribution of the ages of induced cows was skewed, with 25% of cows being 3 yr old. Of the 35% of cows which calved to a single injection of glucocorticoid, 76% were within 30 days of full term based on expected calving dates. Inadequate progress in udder development following the first injection was seen in 11% of cows, of which 78% were more than 30 days premature. Only 56% of cows completed the routine two-injection regime. Dystocia requiring at least moderate intervention occurred in 15 cows (2%). There were no cows with retained foetal membranes (RFM) on 33% of farms, but the overall incidence of RFM in cows receiving routine induction was 14%. No intervention was required for 43% of these, which resolved spontaneously within 48 h of calving. Milk fever was the complication most frequently reported (overall incidence 2.8%) and contributed to 3 of the 6 reported deaths. Preliminary data from 11 farms indicated that 7% of cows were not presented for re-breeding. Only 12% required treatment for anoestrum. The mean calving to 1st service interval was 64 ± 2 days, and 53% had appeared to hold to 1st service.

Influence of reducing wool fibre diameter away from the winter minimum, on fibre length after carding - Smith MC; Bray AR (Proceedings of the New Zealand Society of Animal Production, 1997)
The length of fibres after carding is strongly influenced by the minimum fibre diameter (MinFD) in winter in Low Staple Tenacity (LST) and High Staple Tenacity (HST) Romney sheep. In this study a further weakness was induced by a temporary reduction in fibre diameter at a point away from the winter minimum, and the influence on fibre length after carding (barbe) was determined. Forty adult rams of four genotypes (LST, HST, Drysdale and Merino) were offered a restricted diet for 14 days in early February. Fibre diameter was reduced over the treatment period in LST (by 26%), HST (19%), Drysdale (5.5%) and Merino (0.5%). Barbe was only significantly associated with MinFD during treatment in LST (r²=0.62, P<0.01) and not at all with change in fibre diameter. For each 1 um reduction in MinFD during treatment, barbe was reduced by 1-3mm.

An investigation of techniques used to predict fleece rot incidence in sheep. - Keown A-M; Reid TC (Proceedings of the New Zealand Society of Animal Production, 1997)
Fleece rot is a bacterial exudative dermatitis in sheep (Burrell, 1988) which occurs when the skin has been con-tinuously wet for 4 - 9 days. It is a major predisposing factor to the incidence of bodystrike - a form of flystrike -with a high genetic correlation of 0.9 (Atkins and McGuirk, 1979). This trial investigated the possibility of using fleece colour characteristics to predict the incidence of fleece rot in sheep.

Lamb and hogget growth on different white clover and ryegrass cultivar mixtures in southern New Zealand. - Young OA; Widdup KH (Proceedings of the New Zealand Society of Animal Production, 1997)
Lamb and hogget liveweight gains from five different white clover/ryegrass mixtures were compared at AgResearch, Gore from 1992-1995. The mixtures involved comparisons between white clover cultivars (Huia and Demand), ryegrass endophyte types (endophyte-free and 187BB which produces no lolitrem B) and ryegrass species (Marsden and Greenstone hybrid ryegrasses and Pacific perennial ryegrass). Averaged over 3 years, Marsden/Demand produced significantly greater lamb growth rates and final carcass weights (15.0 cf. 14.1 kg) compared with Marsden/Huia pastures. The advantage in lamb production from Demand based pastures was directly linked to the higher yields of white clover.

Liveweight gain and parasite resistance of lambs treated with slow-release albendazole capsules. - Niezen JH; Robertson HA (Proceedings of the New Zealand Society of Animal Production, 1997)
It has been reported that non-parasitised lambs treated with an oral oxfendazole drench had higher live weight gain and a reduced immune response to gastrointestinal para-sites than untreated controls (Stankiewicz et al., 1994). The aim of this trial was to determine whether treating lambs with controlled-release albendazole capsules had any ef-fect on the performance of non-parasitised lambs fed a low or high protein diet and on subsequent resistance to larval challenge.

Localisation of transforming growth factor Beta1-like immunoreactivity in foetal and mature skin from Romneys and Merinos. - Hocking-Edwards JE; Thomas DG; Birtles MJ; Harris PM; McCutcheon SN; Wickham GA (Proceedings of the New Zealand Society of Animal Production, 1997)
Skin samples removed from sheep foetuses at weekly intervals during gestation were studied to examine how between breed differences in follicle development are induced. Immunocytochemical methods were used to examine the localisation of the peptide transforming growth factor-Beta1 (TGFb1 ). Our observations indicate general localisation of TGFb1 in the skin between 83 and 104 days of gestation in both Romney and Merino breeds. This coincides with the maturation of primary follicles and the development of sebaceous and sweat glands. TGFb1 immunoreactivity was maintained in primary follicles (particularly the presumptive inner root sheath cells in lower regions of the bulb), sweat gland and sebaceous gland but by day 134, a more discrete localisation was observed in the inner root sheath (IRS), outer root sheath (ORS) and sebaceous gland with intense immunoreactivity in the sweat gland. The timing of the localisation and the lack of difference between the breeds suggest that variation in the TGFb1 level is unlikely to have a regulatory role in primary and secondary follicle initiation but may play a role in regulating the diverse differentiation pattern of various cell types within the follicle. The intense immunoreactivity in mature sweat glands suggests a possible osmoregulatory role for TGFb1 in the skin.

Manipulating Ovaries' Follicle Wave Patterns Can Partially Synchronise Returns to Service and Increases the Pregnancy rate to Second Insemination - Macmillan KL; Taufa VK; Day AM (Proceedings of the New Zealand Society of Animal Production, 1997)
The recognised roles of oestradiol in the bovine oestrous cycle include stimulating behavioural symptoms of oestrus, facilitating spontaneous luteolysis and initiating the ovulatory surge of LH. An important ancillary role with progesterone is to inhibit the release of gonadotrophins (Burke et al.,1996). Oestradiol administered by injection or per vaginum can perturb follicle development with consequent effects on responses to superovulation (Bo et al.,1994) and on synchrony patterns (Macmillan et al.,1993). The hypotheses which were tested in the following trial were that injecting a low dose of oestradiol benzoate (1mg ODB) at about mid-dioestrus during the cycle follow-ing first insemination: (i) would not reduce the pregnancy rate to this insemination; but (ii) would alter the pattern of returns to service; and (iii) could affect the pregnancy rate to the second insemination.

Mapping Productive Traits in Livestock - Introduction - Crawford A (Proceedings of the New Zealand Society of Animal Production, 1997)
In the last 7 years a large scale world-wide effort has produced genetic linkage maps of most important livestock species. As a result of this we now have the tools to follow the inheritance of every piece of every chromosome in any pedigree, breed or selection line CIOSS. In addition the methods that enable us to analyse the genes and DNA contained within the chromosomes have undergone many incremental improvements so that it is now a realistic research goal to find and characterise the genes responsible for multigenic or quantitative traits in livestock species.

The measurement of ovine follicle stimulating hormone (FSH) bioactivity utilizing a recombinant human FSH receptor bioassay. - Young W; Henderson K; Hudson N; Moore L; Albanese C (Proceedings of the New Zealand Society of Animal Production, 1997)
Recently a bioassay for human FSH has been described based on FSH stimulation of cyclic AMP production by a Chinese hamster ovary (CHO/FSH-R) cell line stably expressing the human FSH receptor (FSH-R cells). In this study, the viability of this bioassay for measuring ovine FSH was examined. Freshly thawed FSH-R cells were bulked up in culture, and aliquots of 250,000 cells/well dispensed into 48 well culture dishes and incubated overnight at 37°C. The assay culture media was then replaced with 0.25 ml fresh media (α-MEM + 0.1% BSA + 0.25 mM 3-isobutyl-1-methyl-xanthine) containing varying doses of FSH preparations, and the cells incubated for 4 h at 37°C. The assay culture media was then removed and stored frozen at -20°C until assayed for cyclic AMP by radio immunoassay.

Measures of stress and growth suppression in surgically castrated bulls - Carragher JF; Knight TW; Death AF; Ingram JR; Matthews LR (Proceedings of the New Zealand Society of Animal Production, 1997)
The effects of surgical castration of pre- and post-pubertal bulls on measures of stress and growth were investigated in two separate experiments. In Experiment 1, 17-month-old Friesian bulls (n = 6 per treatment) were either left untreated (Controls), handled and administered local anaesthetic (Handled), or handled, administered local anaesthetic and surgically castrated (Castrates). In Experiment 2, 5-month-old Friesian bulls (n = 10 per treatment) were either left untreated (Controls) or surgically castrated without local anaesthetic (Castrates). Castrates in Experiment 1 had higher (P<0.05) plasma cortisol concentrations 7 and 14 days after treatment compared with Handled bulls and lower (P<0.01) gains in body weight for 14 days compared with Controls. There were no effects of treatment on plasma non-esterified fatty acid, b-hydroxybutyrate and urea concentrations. Castrates in Experiment 2 had higher (P<0.05) plasma concentrations of cortisol and the inflammatory protein haptoglobin for 7 days after treatment compared with Controls. The feed intake and weight gain of Castrates were also lower (P<0.05) than that of Controls during the week following treatment. It is concluded that the castration of cattle causes stress, resulting in a check in growth which is possibly mediated via a reduction in feed intake.

Metabolic changes in the mammary gland of sheep prior to, and at, parturition. - Revell DK; Harris PM; Cottam YH; Reynolds GW; Lee J (Proceedings of the New Zealand Society of Animal Production, 1997)
Four sheep fitted with an indwelling catheter in the femoral artery and a transit time ultrasonic flow probe around the left pudendal artery (supplying the mammary gland) were used to quantitate changes in mammary blood flow (MBF) in late pregnancy and lactation, and to determine the extraction of glucose and oxygen by the mammary gland. Mammary vein blood samples were collected by venipuncture. Considerable variation existed in the pattern of change in MBF between individual sheep. In two animals, MBF through the pudic artery fitted with the flow probe doubled to 600 mL/min on the day of lambing (DL), while in the other two sheep, MBF varied little in response to lambing. Possible explanations for this difference between individuals are discussed. Glucose extraction trebled on DL from 6.0 to 18.7% (P<0.01) and remained high during lactation in relation to milk output. Oxygen extraction by the mammary gland peaked during the last week of pregnancy (at 45.7%) and during lactation it was related linearly to milk output.

Methane emission from grazing sheep and cattle - Ulyatt MJ; Lassey KR; Martin RJ; Walker CF; Shelton ID (Proceedings of the New Zealand Society of Animal Production, 1997)
Measurements of methane emissions from individual sheep and dairy cows grazing typical New Zealand perennial ryegrass/white clover dominant pastures are reported. These are the first measurements reported from grazing sheep, and among the first from grazing cattle. The measurement technique, using a marker gas (sulphur hexafluoride), enables emission rates to be determined from analyses of "breath" samples collected while grazing. More than 250 measurements of daily methane emission from 50 sheep (8 months old) were made, with flock-mean emission 18.9±0.8 g/d. Emissions were weakly correlated with feed intake, and they represented a 4.6±0.1% average loss of gross dietary energy. The corresponding mean emission based on 40 measurements of daily emissions from 10 lactating dairy cows was 263±10 g/d, approximately 6.2% of estimated gross energy intake. A notable feature was the large inter-sheep variability in daily methane emission (range 140%) that could not be attributed to variable intake. This would appear to suggest an appreciable diversity of methanogenic response to digestion, and may be significant in the search for strategies to control emissions of this greenhouse gas.

Milksolids response in early lactation to condition score and concentrate feeding - Mudford CJ; Thomson NA; Holmes CW (Proceedings of the New Zealand Society of Animal Production, 1997)
Effects of condition score (CS) at calving and concentrate supplementation over early lactation on milksolids production (MS), liveweight, CS change and intake were investigated in spring 1995. Differential feeding before calving resulted in high CS (HCS) and low CS (LCS) herds of 5.6 and 4.7 (P<0.001) respectively. After calving (10 August) the HCS and LCS herds were split (n=10) and either fed (+) or not fed (-) 3 kg DM/cow/day of rolled barley for 48 days. During the treatment period each herd was offered a similar pasture allowance of 22 kg/cow/day. A 27 day carryover period followed with no supplementation. Treatments were grazed separately throughout. During supplementation the liveweight gain (P<0.01) and change in CS (P<0.05) was greater for LCS than HCS. Cows on + concentrate gained more liveweight (P<0.01) than - concentrate. CS at calving had no effect on milk yield or composition. Concentrate increased (P<0.001) milk, fat and protein yields and protein %. Feeding 144 kg DM/cow of concentrate increased (P<0.001) milksolids by 16.5 kg/cow. No significant interaction occurred between CS at calving and concentrate but for HCS cows the response to feeding concentrates was 21.2 kg MS/cow compared to the response for LCS cows of 11.8 kg MS/cow. During the feeding period, pasture intake was greater (P<0.05) for LCS (12.5 kg/cow/day) than HCS (11.0 kg DM/cow/day). Concentrate had no effect on pasture intake. No treatment effect on pasture intake occurred in the carryover period. These results suggest, that at the pasture allowance post calving of 22 kg DM/cow/day, a CS at calving of 4.7 is adequate to sustain similar milksolids production in early lactation as cows calving with CS of 5.6.

Muscle distribution in lamb progeny from several breeds. - Kirton AH; Duganzich DM; Mercer GJK; Clarke JN; Dobbie JL; Wilson JA (Proceedings of the New Zealand Society of Animal Production, 1997)
Leg and shoulder composition (fat, muscle and bone) and some linear fat and muscle distribution measurements were taken on 458 lambs produced by 39 strains and breeds of ram born in 1992, 1993 and 1994. Lambs were either Romney or Romney-cross. Texel-cross lambs had the highest proportion of muscle in the leg and shoulder cuts with the Poll Dorset-cross lambs having a similar amount. Southdowns, American Suffolks and Romney strains had least muscle, and apart from the American Suffolk, also had most fat. The fat selected Southdown-cross had the highest % carcass fat. There was no significant difference between any of the sire groups in the proportion of the major defatted leg primal cuts. All genotypes had a similar leg muscle cut distribution, breed differences being only in the relative proportions of muscle to fat and bone. The Texel-cross had the highest weight (at the same carcass weight) of psoas muscle and the ultrasonically selected Poll Dorset progeny had the highest proportion of measured lean as longissimus muscle.

Non-invasive pregnancy determination in mares by enzymeimmunoassay of estrone sulphate concentrations in faeces. - Henderson KM; Perkins NR; Wards RL; Stewart JI (Proceedings of the New Zealand Society of Animal Production, 1997)
Measurement of faecal estrone sulphate by enzymeimmunoassay was evaluated as a non-invasive means of monitoring pregnancy status in mares. Faecal samples from non-pregnant mares had a mean ± s.e.m. estrone sulphate concentration of 23 ± 0.9 ng/g (N=242). In pregnant mares, mean faecal estrone sulphate concentrations increased progressively during the first half of gestation. The values rose from a mean ± s.e.m. of 49 ± 4 ng/g (N=121) for samples collected <80 days post-mating, to 122 ± 9 ng/g (N=30) for samples collected 161 to 180 days post-mating. Thereafter, faecal estrone sulphate concentrations remained relatively constant for the remainder of pregnancy. From 150 days post-mating onwards, <2% of faecal samples from pregnant mares had an estrone sulphate concentration below 66 ng/g which was the value 3 standard deviations above the mean value found for non-pregnant mares. Following foaling or foetal death, faecal estrone sulphate concentrations returned quickly to non-pregnant levels. Using this estrone sulphate enzymeimmunoassay, mares may be confirmed pregnant once faecal estrone sulphate concentrations rise above the 66 ng/g cut-off value. Those mares in which faecal estrone sulphate concentrations have not risen above 66 ng/g by 150 days post-mating may be considered to be non-pregnant. Measurement of faecal estrone sulphate thus offers a convenient, non-invasive means of monitoring pregnancy status.

Nutritional effects on Beta-carotene concentrations in the fat of beef cattle. - Boom CJ; Sheath GW (Proceedings of the New Zealand Society of Animal Production, 1997)
Yellow fat reduces the acceptability and value of beef table cuts within the high priced Asian markets. The concentration of carotenoids in fat, leads to this yellowness. A systems experiment which ran for 2 years, studied the effects of nutrition and age on fat carotenoid concentration (FCC). In each year, rising 1-year (R1) and 2-year (R2) Angus steers were offered either full access to winter and spring feed (fast rotation, FR); or were nutritionally restricted during winter (slow rotation, SR) and then given full access to feed during spring. Fat biopsy samples were collected every 4 months and carotenoid concentration determined. FCC increased as animals became older. The effect of the nutritional growth path was to increase FCC during winter where feeding was restricted, particularly in the R1 steers. In both years, the SR systems compensated during spring, with both live weight and FCC being similar for the 2 nutrition treatments by the end of spring. From a practical perspective, farmers who seek to supply beef with satisfactory fat colour should not restrict feeding during the period of 3-4 months prior to slaughter. The experiment also provided data which allowed FCC to be followed from weaning through to slaughter for individual animals. These data provided the opportunity to investigate the prediction of carcass FCC based on earlier fat measurements. Correlations (r) ranged from 0.31 at 24 months to 0.71 at 3 months before slaughter. Correlations are not sufficiently strong to justify early selection of cattle for targeted markets and growth paths. However, there is opportunity for processors to use fat biopsy and objective colour measurement techniques in the selection and purchase of cattle for high priced markets.

Oestradiol Concentrates the Synchrony Pattern in Heifers Treated with Progesterone and Prostaglania F2alpha. - Macmillan KL; Taufa VK (Proceedings of the New Zealand Society of Animal Production, 1997)
Oestradiol has been successfully used to synchronise oestrus and ovulation in anoestrous dairy cows first treated with progesterone for at least 5 days and then injected with oestradiol benzoate (ODB) during the following 24 to 48 h (Macmillan et al., 1994). The ovulatory effects are associ-ated with the ability of oestradiol to induce a surge of LH, especially during pro-oestrus. Although oestradiol has been injected in the period of pro-oestrus following an injection of prostaglandin F2α(PGF), this form of oestra-diol use has not been advocated even though the precision of synchrony is enhanced (Macmillan, K.L.; Burke, C.R.,1996).

Optimum white clover content for milk production. - Harris S; Clark D; Jansen E (Proceedings of the New Zealand Society of Animal Production, 1997)
Nine Jersey and nine Friesian cows in late lactation and housed indoors were fed diets containing either 20, 50 or 80% white clover with the balance perennial ryegrass. During the first 10 days cows were fed ad libitumand during the second 10 days feeding was restricted to 75% of metabolisable energy requirement. Milk yields of cows fed 50% and 80% clover diets ad libitumwere not significantly different but were 18% greater (P<0.05) than for cows fed 20% clover. During restricted feeding, when intakes were not significantly different, milk yields of cows fed 50 and 80% clover were again not significantly different but were 10% higher (P<0.10) than for cows on 20% clover. Clover content had no effect on milk composition. The experiment indicated increased yields weredue mainly to increased intakes associated with high clover diets, and also the higher nutritive value of the clover. Results showed the optimum clover content for milk production was 55-65%.

Parasite resistance: A genome scan approach to finding markers and genes. - Crawford AM; Green R; Cuthbertson RP; Wright C; Vlassoff A; Squire DR; West CJ (Proceedings of the New Zealand Society of Animal Production, 1997)
A systematic approach for finding regions of the genome that are important in the control of productive traits has only recently become available. The advent of microsatellite markers for sheep and other domestic ani- mals (Crawford et al. 1991) and their subsequent place- ment on linkage maps (Crawford eta/. 1995, Kappa et al 1997) has provided a set of highly informative markers densely spread across the genome. With these reagents we now have the ability to follow the inheritance of each region of every chromosome in any cross. Providing we have pedigrees in which genes which have an important influence on the trait of interest are segregating, we can systematically identify the regions of the genome in- volved. This process has become known as the genomic scan.

Plasma potassium - an indicator of protein catabolism in deer? - Jopson NB; Fennessy PF; Thompson JM (Proceedings of the New Zealand Society of Animal Production, 1997)
Elevated plasma potassium (K+ ) concentrations well outside the normal range for deer have been reported during the rut. The effects of season and nutrition on plasma K+ concentration were examined in two experiments in farmed red and fallow deer. In Experiment 1 castrate and entire red stags were fed ad libitum on pasture and blood sampled fortnightly over 11 months. Except for a transitory peak at the beginning of Experiment 1, red entires and castrates showed no abnormal plasma K+ concentrations over the 11 month period. In Experiment 2, a castrate group of fallow bucks were fed to lose a similar amount of live weight as entires over the rut. When plasma K+ concentration was expressed as a function of changes in muscle weight there was a significant negative relationship (P<0.05) in the castrates. There was no relationship in the entires, although the measure of change in muscle weight could have been confounded by changes in water content of the musculature over the rut. The occurrence of hyperkalaemia in deer was variable. Further work is required to clarify the conditions that lead to its expression.

Positional cloning to identify genes. - Montgomery GW; Lord EA; Lumsden JM (Proceedings of the New Zealand Society of Animal Production, 1997)
Target genes, identified by their phenotypic effect, can be located by positional cloning. Current genetic maps in livestock species lack the necessary detail for direct application in these projects. Fine maps of each target region must be developed using a variety of strategies. These include chromosome specific libraries and comparative mapping. A physical map of the region is generated by identifying overlapping clones containing large DNA inserts. All genes from the region are sought and candidate genes identified. The resources being developed in livestock projects, including the search for the Booroola (FecB) locus, and complete expression maps for the human genome will greatly facilitate future positional cloning projects in livestock.

Progeny performance of industry and index selected Angus bulls. - Enns RM; Nicoll GB (Proceedings of the New Zealand Society of Animal Production, 1997)
The Department of Lands and Survey (LS) introduced an objective-based, open nucleus Angus breeding program in 1976 to produce bulls for its commercial properties. Previously, commercial sires were purchased from numerous industry sources (IND). To demonstrate the usefulness of objective selection and to determine performance differences between the two sire sources, 600 mature Angus cows and heifer replacements were randomly mated to either LS or IND bulls beginning in 1976. Replacement female offspring from these matings were then randomly mated to either LS or IND bulls to produce second generation offspring (GEN2). Herd size was maintained and matings continued through 1986. Growth performance of all GEN2 animals was recorded through weaning. After weaning, only female performance was recorded. Least-squares methodology was used to determine differences between the two genetic sources (IND or LS). Traits measured were weaning weight (WW); cow ratio, calf weaning weight per 100 kg of cow weight (CR); yearling weight (YW); and 18 month weight (18M). The statistical model for all traits included year of birth (YOB), sire source of calf (CSS) and dam (DSS), sex (where applicable), age of dam (AOD), age at weighing, and the interactions of YOB and CSS, YOB and DSS, AOD and CSS, AOD and DSS, and CSS and DSS. Calf`s sire source was significant (P<.01) for WW and CR, and approached significance for YW (P<.1) but was not significant for 18M (P>.1). Dam`s sire source was not significant for any trait (P>.1) nor was the interaction of CSS and DSS (P>.1). The WW of progeny with LS maternal grandsires and LS sires was 4.6±1.8 kg greater than progeny with IND sires and IND maternal grandsires. Differences in weights taken subsequently were smaller. Although not statistically important, in a production scenario where all male progeny were sold at weaning, benefits of the introduction of an objective-based, breeding scheme were evident.

Progress with selection to change age at puberty and reproductive rate in Angus cattle. - Morris CA; Wilson JA (Proceedings of the New Zealand Society of Animal Production, 1997)
Trying to improve beef cow pregnancy rate by genetic selection within a breed is generally considered to be slow and difficult. We have investigated a promising option which involves selecting to change age at puberty in heifers and then exploiting the genetic correlation with lifetime pregnancy rate. Angus herds were established from a common foundation population in the early 1980s, and were then selected from 1984 for reduced age at puberty (AGE-) or increased age at puberty (AGE+), with a control herd for comparison. Relative to the AGE+ herd, heifers born in the AGE- herd in 1993 and 1994 were 83 days (=20%) younger at puberty (P<0.001), and their half brothers had 2.0 cm (=6.6%) greater scrotal circumference (P<0.001). Corresponding live weights in the AGE- herd were 17% less at puberty (P<0.001), not significantly different between herds at birth, weaning or 8 months of age, and 3.5% higher as yearlings (P<0.01) than in the AGE+ herd. Conception rates for the 1992-95 matings were 91.2 and 71.2% (P<0.001) for AGE- and AGE+ yearling heifers, but not yet significant at 89.6 and 85.0% respectively for older cows. Restricted maximum likelihood estimates of heritability for age at puberty and scrotal circumference (mean of 3 measurements) were 0.27±0.04 and 0.48±0.05, with a genetic correlation of -0.29±0.10. Phenotypic standard deviations for age at puberty in the AGE- and AGE+ herds were 51 days for each herd. However, within-herd heritabilities for age at puberty were 0.32±0.11 and 0.13±0.14 for the AGE- and AGE+ herds, respectively, which suggests to us that different modes of inheritance should be investigated in each herd.

Protein-tannin complexes are susceptible to proteolytic degradation. - Diaz-Hernandez A; Nixon MJ; Ball FM; Leng RA; Rowe JB (Proceedings of the New Zealand Society of Animal Production, 1997)
In vitro studies were carried out to determine the factors that affect formation and dissociation of the protein-tannin complex (PTC) under conditions simulating those found in the digestive tract of the ruminant. For this study purified condensed tannins (CT) from the following tropical plants were used: Acacia harpophylla, Acacia aneura, Acacia saligna, Acacia holosericea, Tipuana tipu, Albizia chinensis, Flemingia macrophylla, Grevilea robusta, Casuarina cristata, Casuarina cunninghamiana, Azadarachta, Leucaena leucocephala, Leucaena pallida and Leucaena diversifolia. English spinach was selected as the source of soluble protein and during the growing phase, the plants were exposed to a 14C-CO2 atmosphere for 48 h. Following exposure, the foliar protein ribulose 1,5 biphosphate carboxylase/oxygenase, (rubisco) was isolated. The radioactive labelled protein was incubated with the isolated samples of CT for 2h at 39°C. The mixtures were then centrifuged and the percentages of bound protein (precipitate) and unbound protein (fluid phase) were determined. Formation of the protein-tannin complex (PTC) occurred over a range of pH 3-7. Above this pH 7, no PTC was formed. To determine the effects of pH on the dissociation of the PTC, the precipitate was incubated with buffers over a range of pH 3-9. It was found that acidic or alkaline pH was responsible for only 8 and 14% of the dissociation of the PTC, respectively. However, addition of abomasal and intestinal fluid from both sheep or cattle increased dissociation of PTC to more than 60%. Further analysis showed that pepsin and trypsin are largely responsible for the dissociation which occurs with the abomasal and intestinal fluids respectively.

The relationship between compounds causing scourable diffuse yellow and the yellowness of clean and greasy wool. - Wood JE; Reid TC (Proceedings of the New Zealand Society of Animal Production, 1997)
As part of a study of the chemistry of wool yellowing, a pilot survey was conducted to examine the frequency of occurrence of two yellow compounds previously isolated from the suint of a few yellow fleeces. The relationship between the amounts of these compounds present and the degree of discolouration was examined in clean and greasy wool from Merino (n = 48), Halfbred (n = 12), Corriedale (n = 26), Romney/Crossbred (n = 52), Cheviot (n = 10) and Perendale sheep (n = 8). The numbers of samples analysed, the mean yellowness (tristimulus Y-Z) and the relative proportions of the two yellow compounds detected are given in Table 1. Because not all the data was obtained for all samples, the number of data points used in each analysis may vary from those in this table. Of the 172 wool samples examined, one yellow compound was present in all of them, and a second yellow compound in 91%. There was little relationship between the amounts of these compounds and the yellowness of the greasy wool. Furthermore, there were no significant relationships between the amounts of either compound and the yellowness of the clean wool. The results suggest that the coloured compounds isolated are universally distributed in the wool of New Zealand sheep and may be responsible, in part, for the degree of yellow discolouration in greasy wool. They would appear to have little, if any, impact on the colour of clean wool.

Removal of cisternal milk following milk accumulation for 9 hours does not increase total yield during once-daily milking - Farr VC; Davis SR; Stelwagen K (Proceedings of the New Zealand Society of Animal Production, 1997)
Once-daily milking (ODM) of dairy cows in New Zealand results in a yield loss of 15-25% (Carruthers V.R. et al.,(1993)). This loss is not associated with the total storage capacity of the udder, although some studies have shown that increase in the volume of milk in the cistern is associated with reduced yield loss during ODM (Knight C.H. and Dewhurst R.J. (1994)). The following experi-ment was undertaken to determine whether removal of cisternal, but not alveolar milk, at the p.m. milking, de-creased the production loss during ODM.

The responses of lactating cows treated for anoestrus to an oestradiol capsule or an oestradiol injection. - Taufa VK; Macmillan KL; Nation DP; Day AM; Ashcroft MJ (Proceedings of the New Zealand Society of Animal Production, 1997)
Postpartum anovulatory anoestrus is a mjor form of infertility among cows in dairy herds inNew Zealand. The currently recommended treatment involves a 5-day prim-ing with progersterone (P4) released from a CIDR TM device (InterAg, NZ), with a 10 mg gelatin of oestradiol benzoate (ODB) and 1 g lactose capsule (CIDR TM; InterAg, NZ) placed in the grooved surface of the device preceding device insertion, and an injection of ODB (CIDIROLTM ; InterAg, NZ) given intramuscularly at 24 to 48h following device removal.

Responses to protected amino acids or protected protein in dairy cows grazing ryegrass pastures in early lactation. - Rusdi; Van Houtert MFJ (Proceedings of the New Zealand Society of Animal Production, 1997)
Two-hundred-and-four Friesian dairy cows (4-9 years old) were allocated to 1 of 9 groups at calving (n=22-23) in August-September 1995. All cows grazed ryegrass pastures at a stocking rate of 3.1 cows/ha and received some maize silage and barley for the first weeks after calving. In addition, they received one of three experimental supplements in early lactation (weeks 2-11) or mid lactation (weeks 12-22) or late lactation (weeks 23-33). Experimental supplements were 1 kg/d barley only (BAR), 1 kg/d barley with 17 g/d protected methionine/lysine (BML) or 1 kg/d protected protein meal (PPM). Individual pasture intake was estimated twice (5 days) during each lactation stage with sub-groups of cows (n=8) using the alkane technique. Preliminary results for cows in the early and late lactation groups are presented. In cows supplemented in early lactation, supplement intake was lower than anticipated (BAR, BML and PPM: 0.73, 0.67 and 0.41 kg/d respectively). Mean pasture intake (17.4 kg dry matter [DM]/d), milk solid production (2.07 kg/d) or changes in live weight (+23 kg) and body condition (+0.02) did not differ between groups. Gross milk composition and milk protein composition were also unaffected. In cows supplemented during late lactation, supplement intake was 0.83, 0.84 and 0.68 kg/d for groups BAR, BML and PPM respectively. Mean pasture intake (14.3 kg DM/d), milk solid production (1.49 kg/d) and change in live weight (+11 kg) during the period of supplementation did not differ between groups. Although further work with higher levels of supplementation with protein or amino acids is required, these results suggest that neither MP supply nor methionine/lysine supply were limiting milk production in dairy cows grazing ryegrass-based pastures during early or late lactation.

The role of calsequestrin in muscle function. - Trumble W; Wesson C; Jones KR; Uljee AE; Wrigglesworth AL (Proceedings of the New Zealand Society of Animal Production, 1997)
Meat quality depends on muscle quality which is related to the regulation of muscle function by the contrac-tion-inducing ion, calcium. If the process of Ca 2+ uptake, sequestration or release at the level of the muscle cell is interrupted or altered, there is a loss of muscle quality. Two well-characterized conditions that result directly from al-tered Ca2+ regulation are porcine malignant hyperthermia and chicken crook neck syndrome.

Seasonal changes in fibre and follicle characteristics related to wool bulk in Perendale ewes. - Dick JL; Sumner RMW (Proceedings of the New Zealand Society of Animal Production, 1997)
Wool bulk is one of six key characteristics that describe processing performance and the final potential of wool products and is largely influenced by fibre crimp and fibre diameter. Measurements of seasonal variation in wool growth, and fibre and follicle characteristics associated with wool bulk were made over 19 months in Perendale ewes within lines selected for or against wool bulk to assess their potential impact on processing performance. Wool growth rate, mean fibre diameter, mean follicle depth and follicle activity displayed a minimum value in July and a maximum in December-January. Mean fibre curvature and follicle curvature grade had an opposing seasonal trend with a maximum in winter and a minimum in summer. The opposing seasonal cycles for fibre curvature and fibre diameter, compensated each other across seasons with no change in the expression of wool bulk throughout the year.

Seasonal Patterns in Production and Quality of Semen of Rams from Flocks Selected for or against an Early Breeding Season. - Smith JF; Parr J; Smith JK; Briggs RM; Duganzich DM (Proceedings of the New Zealand Society of Animal Production, 1997)
Seasonal patterns of semen production and sperm quality from rams of different breeds have been previously reported (Colas, 1979). Flocks within a breed have been selected for differences in seasonal lambing patterns based on ewe lambing date (Smith, et al.,1992). This trial reports the effects of this selection on the production and quality of semen from rams in those flocks.

Sheep breeding objectives and selection criteria of Wairarapa and Tararua sheep farmers - Gavigan RG; Parker WJ (Proceedings of the New Zealand Society of Animal Production, 1997)
The adoption of recommended breeding practices, such as the use of performance recorded rams and objective selection of flock replacements, by sheep farmers is believed to be poor. This issue was investigated through a stratified random interview survey of 74 Wairarapa and Tararua wool growers. Equal emphasis was placed on breeding for wool and meat production by 73% of the farmers surveyed. Only 23% quantified their breeding objectives numerically in terms of wool production, lambing performance or carcass weights. Criteria, scored on a 4 point "importance" scale (1 = No; 4 = Great), for ewe hogget selection were: structural soundness (3.8 ± 0.1; mean score ± se) absence of black fibres (3.7 ± 0.1); visual body size (3.5 ± 0.1), wool characteristics (3.0 ± 0.1) and face cover (3.0 ± 0.1). Fleece and live weight recording was used by 22 and 54% of the farmers, respectively, for ewe hogget selection. Ram selection criteria were similar as those for ewe hoggets, with measured fleece weight (3.4 ± 0.1) and selection index (3.1 ± 0.1), both being rated lower on average than structural soundness, conformation and body size. Farm management consultants and WoNZ Production Officers were rarely consulted for advice on ram selection (mean score 1.2 and 1.1 on 5-point scale) in comparison to ram breeders (2.9) and other farmers (1.8). The decision on whom to purchase rams from was most commonly made on the basis of the breeder`s reputation (29%) and similarity of farm type (19%). Price (1%) and breeder advertisements (1%) were not identified as important determinants of whom to buy rams from. Overall, the survey confirmed a general lack of objectivity in sheep breeding and selection decisions. More effective ways of promoting the value and use of objective sheep breeding information to sheep farmers are required.

Short-Term Grain Feeding and its Effect on Carcass and Meat Quality. - Morris ST; Purchas RW; Burnham DL (Proceedings of the New Zealand Society of Animal Production, 1997)
Forty-five crossbred steers weighing 540-580 kg were assigned to three treatment groups. Group 1 received pasture only for 58 days; Group 2 grazed at a similar herbage mass to Group 1 and were supplemented with 4 kg/hd/day of a concentrate ration; Group 3 were on a feedlot and fed 8 kg/hd/day of concentrate together with 2.0 kg/hd/day of straw. Groups 2 and 3 each had a 28 day pre-conditioning period followed by a 30 day concentrate feeding period. Final fasted liveweight, liveweight gains, and carcass weights for concentrate, concentrate plus pasture and pasture alone groups were 546 ± 9, 548 ± 9, 547 ± 8 kg; 0.33 ± 0.09, 0.42 ± 0.09, -0.05 ± 0.09 kg/hd/day and 293 ± 7, 315 ± 4 and 313 ± 4 kg, respectively. The concentrate plus pasture and pasture only fed groups had greater fat depths. Ultimate pH was slightly lower in concentrate fed than pasture fed cattle but there were no differences in fat colour or tenderness as measured in the laboratory. Plasma carotene levels were significantly lowered by a factor of 10 in the concentrate fed group compared to the grass fed group, but this did not affect fat colour when measured subjectively at the meat processing plant or objectively in the laboratory. Apparently feeding concentrates for 30 days is insufficient to affect fat colour characteristics.

Sire by finishing environment interactions for carcass and meat quality traits in beef cattle. - Charteris PL; Garrick DJ; Morris ST (Proceedings of the New Zealand Society of Animal Production, 1997)
Genotype by environment interactions can result in bulls having different genetic merits applicable to different environments. Beef cattle have traditionally been finished on pasture in New Zealand. The desire to meet perceived market requirements for meat quality has encouraged progeny testing and led to feedlotting. The objectives of this study were to evaluate sires on the basis of performance of their pasture-finished steer progeny, their feedlot-finished steer progeny and to compare the assessments of these sires from offspring in each environment. Fourteen Angus sires had progeny in both environments comprising 54 pasture-finished steers and 148 feedlot-finished steers. Estimated Breeding Values (EBVs) of each sire were obtained separately for eight traits that were measured for both pasture and feedlot progeny. Product-moment correlations between sire EBVs based on pasture-finished progeny and EBVs based on feedlot-finished progeny averaged 0.11 (range -0.16 meat colour to 0.50 subcutaneous fat depth). The expected distributions of these correlations between EBVs were obtained by simulation for a range of null hypotheses determined by the true genetic correlation between performance in the two environments using Monte Carlo simulation. The expected distributions of correlations between environments were determined for differing numbers of progeny per sire and for the effect of preselecting prior to entering the progeny test. The distributions of correlations were used to determine whether the low observed correlations between EBVs estimated from each environment were likely to have arisen from chance sampling or were truly indicative of genotype by environment interaction. Based on actual progeny numbers per sire in each environment there were significant (P=0.05) sire by finishing environment interactions for most traits analysed. Increasing the number of progeny per sire would increase the chance of detecting such interactions, in that case separate progeny testing programmes for each environment may be necessary.

Sources of variation in the ultimate pH of M. longissimus from prime steers. - Purchas RW; Keohane BE (Proceedings of the New Zealand Society of Animal Production, 1997)
The ultimate pH (pHult) of beef is an important quality determinant, that can be affected by pre-slaughter muscle glycogen concentrations. The two trials reported here evaluated relationships between pre-slaughter conditions and behaviour of mobs ofsteers processed at Manawatu Beef Packers Limited and the subsequent incidence of high-pH beef. Trial 1 involved 405 2- and 3-year steers in 12 mobs, with a mean (±sd) carcass weight of 341.2 (±28.2)kg. Cattle were held for either c. 3h prior to slaughter (1/2of each mob) or c. 27h. Mean carcass weight was lower for the 27h-mobs (P < 0.01), but the extra 24h holding time had no effect on mean pHult , bruising score, carcass fat depth, or meat colour. The percentage of carcasses with a pHult> 6.0 varied from 0 to 27%, but was not closely related to any of the pre-slaughter conditions monitored (eg. feeding levels, conditions during yarding, loading and transport,weather conditions, and conditions at the plant).

Technology design and marketing: Case studies for beef cattle breeding - Parminter TG; Wilkinson RS; Tarbotton IS; Carter JC; Perkins AML; McMillan WH; Smeaton DC (Proceedings of the New Zealand Society of Animal Production, 1997)
An assessment of farmer beliefs and attitudes to predict likely use of new beef breeding cow technologies was undertaken with farmers from Northland, King Country, and Hawke`s Bay. In workshops, farmers evaluated the use of twinning through embryo transfer, artificial insemination with sex-sorted encapsulated semen, and terminal sires. The proportions of farmers likely to use the technologies to some extent, were 55, 72, and 83% respectively. Farmers identified the important interactions that would be expected to occur if the technologies were introduced into typical beef farming systems in their area. Attitudes towards each technology and towards selected technology attributes, indicated important considerations for future development of the technologies. These included their ability to: improve breeding cow returns; achieve easy care calvings; and integrate with sheep enterprise management to provide leafy feed for lambs. Consideration of these attributes in technology research, development, and marketing, is likely to improve technology uptake.

Time to change' - Davis SR (Proceedings of the New Zealand Society of Animal Production, 1997)
The topics discussed in the fifty-six Presidential ad-dresses preceding this one can be broadly categorised into those that are personal statements on personal research areas and those that are ‘tub-thumping’ about the Society or agricultural research in general. In recent times, Presidents Sykes ( 1986), Jury (1990) and Nicol (1992) have all thumped their tubs and exhorted the Society to change both in attitude and modus operandi. Alas, their exhortations have had little impact. They pointed the direction but we did not follow. So it is my intention to try again, for the simple reason that if we do not change, we will not survive as a Society, or maybe even as animal scientists.

Translation of information between human and livestock gene maps using a deer interspecies hybrid mapping panel. - Tate ML; Mathias HC; McEwan KM; Anderson RN (Proceedings of the New Zealand Society of Animal Production, 1997)
The burgeoning knowledge associated with the gene maps of humans and mice can provide key information for the identification of genes underlying production traits in livestock. In tbeo~~, it should be possible to tramlate information associated with a human chromosomal location to a chromosome location in sheep, cat& or deer. However, in practice, livestock gene maps often require more comparative links to make accurate &anslation possible. We have taken a novel approach to livestock comparative mapping by using an interspecies hybrid mapping panel to map both gene loci and sheep and cattle microsatellites. The panel comprises DNA from 346 l/4 Pere David’s deer (Ekxphurus dnvidinnuj 3/4 red deer (Cervus elaphur) backcross progeny of male FI P&e David’s deer x red deer hybrids. We are using this deer mapping resource to relate the sheep, cattle and human gene maps and by mapping key markers from each.

The use of fly attractants to encourage flystrike for sheep selection purposes. - Blackwell GL; Potter MA; Cottam YH; Blair HT (Proceedings of the New Zealand Society of Animal Production, 1997)
The incidence of flystrike in New Zealand flocks is about 3% in most years. This low level of prevalence makes it difficult to discriminate between potential flock replacements based on naturally occurring flystrike. Selection decisions could be improved if either the rate of flystrike could be raised artificially or an easily measured trait that has a higher level of occurrence could be found. The second approach is used in Australia where fleece-rot has both a higher incidence rate than flystrike and is highly genetically correlated to susceptibility to flystrike. However, the incidence of fleece-rot in New Zealand dual-purpose sheep is not sufficiently high to allow its use as an indirect indicator. In a effort to find a means of artificially increasing the incidence of flystrike, groups of hoggets were brought indoors and exposed to the Australian green fly Lucilia cuprina. In total, 5 trials (10 animals/treatment) were run to compare: the susceptibility of Romney vs Perendale sheep, using wetting, dung or homogenised liver as attractants. Wetting was applied along the back from a watering can while the other attractants were applied to a patch on the shoulder, mid-back and rump. About 2000 gravid flies were released into a fly-proof room along with the penned sheep. The main results of these trials were: a) It was very difficult to get an established maggot population on clean wet sheep; few eggs were laid and no cases of established strike occurred; b) Dung acted as a moderately successful attractant; maggots were hatched on the sheep but none developed to the skin penetrating stage; c) Liver acted as a very successful attractant and maggots developed on all treated sheep. No between-breed differences occurred with wetting, dung or liver attractants. Further studies are required to refine the use of attractants. In particular, an attractant that is less powerful than homogenised liver but more potent than wetting or dung is required before moving onto large-scale field trials.

Use of pregnant dairy cows in product development of the intravaginal progesterone releasing (CIDR) device. - Burke CR; Burggraaf S; Bunt C; Rathbone M; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 1997)
This study aimed to confirm that pregnant cows could be used to study release rates of progesterone (P4), the hormone of ‘pregnancy’, from the CIDR device without compromising pregnancy. The seasonal nature of the New Zealand dairy operation presents only a brief window for large scale CIDR studies, if the treatment system is limited to non-pregnant cows.

Use of teaser ram effect to advance lambing date in a farm systems study - Smeaton DC; Webby RW; Sheath GW (Proceedings of the New Zealand Society of Animal Production, 1997)
The normal onset of seasonal oestrous behaviour in Romney derived breeds can be advanced by the use of teaser rams and social facilitation. This technique was used, as part of a farm systems trial, to advance the start of lambing from September 1 to August 1. In the first year, the use of Dorset rams at ratios of 0, 3, 6 and 9 per 100 ewes resulted in 0, 72, 81 and 86% respectively of ewes ovulating at the silent oestrous. In the following year, a ratio of 8% was used in combination with CIDRs after the silent oestrous. This extra manipulation gave no advantage in terms of ewes lambing and ewes lambing multiples. Use of Coopworth rams instead of Dorsets and priming the teaser rams by exposure to oestrogen treated spayed ewes likewise had little impact. Over all years, teasing resulted in a similar proportion of ewes lambing (87%) compared to the later lambing non-teased groups (89%). However, the early groups had only 37% multiple births compared to the late lambing ewes (48%, P<0.01). The 31 day advance in start mate date in the early ewes resulted, on average, in a 27 day advance in mean lambing date (P<0.01). When weaned on the same date the early lambs were 2.27 kg heavier than the late lambs (P<0.01).

Volume measurement of wool samples. - Merrick NC; Scobie DR (Proceedings of the New Zealand Society of Animal Production, 1997)
A rapid procedure for measuring the volume of wool samples was developed, using a gas pycnometer. Volume was measured on midside wool samples, harvested monthly, from thirteen sheep breeds representing a range of wool medullation categories. Clean sample weights between two and ten grams and the fourth sequential volume measurement are recommended. Volume was also calculated, using the sample mass and the theoretical density of wool. Measured and calculated volumes were the same for non-medullated wools (p=0.20), but not for highly medullated wools, the measured volume was 25% greater than the calculated volume (p<0.001).

The accumulation and clearance of equol in the blood of ewes grazed on either high or low formononetin red clovers - Kramer R; Keogh RG; McDonald MF (Proceedings of the New Zealand Society of Animal Production, 1996)
Formononetin is the major red clover phytoestrogen responsible for reproductive dysfunction in sheep. Formononetin is metabolised in the rumen to equol which is significantly more oestrogenic. This study was conducted to characterise the accumulation of conjugated and free equol in the blood of ewes grazed on either high formononetin (cv Pawera, 0.57% of dry matter) or low formononetin (cv G27, 0.25% of dry matter) red clovers over a 1, 2 or 3 week period and the subsequent clearance of equol after removal from the red clover. Seventy mixed age ewes were divided into 7 treatment groups (n=10). Each group grazed either Pawera or G27 red clover for 3, 2 or 1 week or ryegrass (control group) prior to mating as one flock on ryegrass pasture. All ewes were regularly blood sampled. Once mated, the ewes were laparoscoped and returns to service recorded. Conjugated equol concentrations in both Pawera and G27 ewes increased over the first 2 days to 23.97

Across breed evaluation of dairy cattle - Harris BL; Clark JM; Jackson RG (Proceedings of the New Zealand Society of Animal Production, 1996)
Genetic analysis of dairy cattle has been undertaken using an animal model including pedigree records since 1940 and performance records since 1986. The animal model analyses all breeds and breed crosses simultaneously allowing accurate estimation of hybrid vigour effects for milk production, liveweight, four survival traits and 16 linear type traits. The animal model allows the effects of induction, age at calving and herd- year-season to be taken into account when estimating an animal

Animal behaviour and stress: impacts on meat quality - Carragher JF; Matthews LR (Proceedings of the New Zealand Society of Animal Production, 1996)
Animal behaviour can deleteriously affect meat quality through three different pathways: exertion/activity, physiological stress responses and perceptions of welfare. In this review of published work we will describe each pathway, and discuss methods for minimising their impacts on both the physicochemical and animal welfare aspects of meat quality. We conclude that whereas the physicochemical quality of meat can be improved by some post-slaughter carcass handling treatments, public perceptions of meat quality can only be enhanced by improved animal handling practices to reduce stress.

Assessing the value of breeding technologies to dairy farmers - Rendel J; Jackson R; Harris B; Allison T; Shannon P; Burton L; Tempero H (Proceedings of the New Zealand Society of Animal Production, 1996)
The adoption of technologies for breeding dairy cattle requires estimating the financial return to dairy farmers in conjunction with assessing the financial implications to the breeding company. This paper describes a procedure currently used by the Livestock Improvement Corporation. The net on-farm income generated as a result of the new technology is calculated. This is discounted to a Net Present Value allowing for the cost of the technology. A positive NPV indicates the adoption of the technology is of benefit to the dairy farmer. The breeding company also should assess the funding implications of any change. Typically this is expressed in terms of the increase/decrease in price of products and services.

Assessment of female traits for genetic improvement of fertility in dairy cattle - Grosshans T; Xu ZZ; Burton LJ (Proceedings of the New Zealand Society of Animal Production, 1996)
The objective of the present study was to investigate the suitability of various fertility traits for describing the reproductive performance of dairy cows in New Zealand. Using a data set from herds participating in the Livestock Improvement Sire Proving Scheme over the 1986/87 to 1992/93 seasons, the following female fertility traits have been investigated. Based on the start of mating (STOM) in a particular herd, the intervals from STOM to first mating (SMFM) and to the successful mating (SMCO) were calculated and compared to the internationally used traits that are based on the calving date, such as, calving to first mating (CFM) and calving to successful mating (days open, DO). Further traits considered are age at calving (AC), number of matings per conception (NS), first to successful mating (FMCO), calving interval (CI) and two traits that indicate whether a cow became pregnant within 21 or 42 days of STOM (PR21, PR42). The traits defined for the unique conditions in New Zealand, SMFM, SMCO, PR21 and PR42 emphasize the economic importance of reproduction to dairy production. The comparison to overseas studies using DO, FMCO and CI showed that New Zealand dairy cows had a better fertility performance than overseas cows.

Associations between milk protein genetic variants and production traits in New Zealand dairy cattle - Winkelman AM; Wickham BW (Proceedings of the New Zealand Society of Animal Production, 1996)
Records on 7574 first lactation cows were used to investigate the associations between milk protein genetic variants and 305-day milk, fat, and protein yields. Friesians, Jerseys and Ayrshires and their crosses were represented in the data. Milk samples were typed for 3 casein (CN) proteins as1-CN (B,C), b-CN (A1, A2), k-CN (A,B) and 1 whey protein b- lactoglobulin (LG) (A,B). The model used to describe the data included the additive genetic effect of animal and the four protein phenotypes. The interaction between breed and as1-CN phenotype and between breed and b-CN phenotype was significant (P<0.05) for milk, fat and protein yields while the interaction between breed and k-CN phenotype was significant (P<0.05) only for protein yield. The interactions associated with the as1-CN and k-CN phenotypes were scale effects while the interactions associated with b-CN resulted from reranking of protein phenotype across the breeds. Friesian and Jersey as1-CN BB cows had higher (2.8% and 0.8%, respectively) milk production and lower (0.3% and 1.2%, respectively) protein production than BC animals while the differences between the phenotypes for fat production were small. The b-CN A2 allele was associated with increased production in the Friesians with A2A2 cows producing approximately 2% more milk, fat and protein than A1A1 cows. The opposite effect was found in Jerseys where A2A2 cows produced 3-4% less milk, fat, and protein than A1A1 cows. The B allele of k-CN was associated with a 0.6 to 3.5% increase in production. The b-LG BB phenotypes produced approximately 1.3% less milk and protein and 1.2% more fat than the AA phenotypes. The dominance effect was not significant (P<0.05) for any of the protein phenotypes.

An attempt to create an 'anoestrous cow' model by restricting feed allowances in non-lactating cyclic cows - Burke CR; Verkerk GA; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 1996)
This experiment aimed to characterise the ovarian response to reducing live-weight (LWT) with the view of creating nutritional anoestrus in cyclic cows. The ovaries of 8 non-lactating 3 yr old Friesian cows were ultrasounded daily during 5 synchronised oestrous cycles (Rounds 1 to 5) over 12 months. An initial live-weight of 445

Brief Communication: Alpaca management in the Central North Island of New Zealand - Nelson ID (Proceedings of the New Zealand Society of Animal Production, 1996)
The high South American altiplano is not the ideal environment for alpacas but was forced onto them by the introduction of sheep and cattle to the Inca pastures following the Spanish conquest. In New Zealand they are being farmed in a variety of areas and seem to respond dramatically to our normal farming methods. Warm, humid areas can cause problems with eczema and staggers. Alpacas produce a semi-precious fibre of various colours, which at present is causing processing difficulties in New Zealand due to the small quantities, so we are concentrating on increasing herd numbers. Alpaca management can be closely allied to sheep farming, with the exception of their mating and breeding. They are induced ovulators and can be mated in either pens or paddocks. Pen mating gives better control but is more work, while paddock mating has the disadvantage of prolonging the breeding season. Alpacas will breed at any time of year, but we have found that the autumn suits them best and they are remated two weeks after birthing. Alpaca twins are extremely rare. They are a hardy, easy care animal that will do well on untopdressed native pastures and when run in isolation seldom get internal parasites, but can pick up lice or mites. We are still learning what suits alpacas best, bearing in mind that these are very adaptable animals that do not need alterations to their environment to suit any specific needs.

Brief Communication: Automatic oestrus detection from milking data - a preliminary investigation - Sherlock RA; Smith LA; Mitchell RS (Proceedings of the New Zealand Society of Animal Production, 1996)
The solid fat content of milkfat has a major influence on the hardness of butter produced at dairy factories. The aim of this work was to study the variation in the solid fat content of milkfat from thirty herds in the factory collection area on a single dayto determine the extent of variation in the milk supply. The solid fat content of the milkfat at 10°C varied from 49.6% to 59.8% between the individual herds. This variation in the milk from different herds is as large as the entire seasonal change observed in the bulked factory silo milk, indicating significantvariation in the properties of the milkfat within the factory supply on a single day. Low solid fat content at 10°C was correlated with milk of low fat percent (r = 0.78, P< 0.0005) and high protein-to-fat ratio (r = -0.75, P< 0.0005). Though there was substantial variation in the solid fat content within the breeds, milkfat from Friesian herds had a significantly lower solid fat content than milkfat from Jersey herds (mean ± S.E., 54.4 ± 0.6 and 57.1 ± 0.6 respectively, P = 0.004). There appears to be considerable potential for exploitation of the natural variation in the properties of milkfat inherent in the New Zealand dairy herds.

Brief Communication: Binding of nuclear proteins to the bovine alpha- lactalbumin gene promoter - Kuys YM; Snell RG; Wheeler TT (Proceedings of the New Zealand Society of Animal Production, 1996)
The production of milk during lactation requires tran-scriptional activation of milk protein genes. This is facili-tated by the binding of nuclear factors to the gene promoter. The DNA binding activity of some of these factors appears to be controlled by lactogenic hormones, although many aspects of this process are not understood. Determining the precise molecular mechanism of transcriptional control and which nuclear factors are involved will facilitate the manipulation of milk composition. Recently, a transcrip-tion factor called Stat5 has been shown to be required for the activation of the rat β-casein gene (Schmitt-Ney et al., 1991), the sheep β-lactoglobulin gene (Burdon et al.,1994) and the rat whey acidic protein gene (Li and Rosen, 1995). This protein is activated during late pregnancy and through-out lactation in the mammary gland of mice (Schmitt-Ney et al.,1992). We have used the Stat5 DNA recognition sequence in this study to investigate the activity of Stat5 in the bovine mammary gland.

Brief Communication: Effect of atropine on milk protein composition of dairy cows - Prosser CG; McLaren RD (Proceedings of the New Zealand Society of Animal Production, 1996)
Milk production by dairy cows and yield of the compo-nents, fat, protein and lactose are closely related to nutritional intake. The individual proteins in milk respond differently to a change in nutritional status, giving rise to significant differ-ences in milk protein composition (DePeeters and Cant, 1992). For instance, Gray and Mackenzie (1987) noted a decrease in α-lactalbumin and increase in serum-derived proteins, serum albumin and immunoglobulin, in animals on restricted pasture for 10 days. Although β-lactoglobulin concentration decreased, the response was not significant. Treatment of concentrate-fed dairy cows with a single injection of atropine caused a similar, though temporary, decrease in milk yield, total protein and α-lactalbumin content of milk (Roets and Peeters, 1981). Changes in other milk proteins were not evaluated. The observed responses arise from the ability of atropine to rapidly and specifically depress plasma amino acids used for milk protein synthesis and provide a means of experimentally manipulat-ing supply of substrates for milk protein synthesis. The present study was designed to evaluate the use of atropine in pasture-fed cows.

Brief Communication: Effect of dietary vitamin A on plasma carotenoid concentration and fat colour in cattle - Knight TW; Death AF; Wyeth TK (Proceedings of the New Zealand Society of Animal Production, 1996)
In two trials using cattle grazing green pasture, daily supplements of 1x106 IU vitamin A decreased plasma carotenoid (PC) concentration by 43- 58% over 28-31 days. Neither increasing the dose of vitamin A to 2.5 x 106 IU nor continuing the supplement for 83 days further reduced PC concentrations. These decreases in PC concentrations were not accompanied by decreases in carotenoid concentration in the subcutaneous fat or fat colour. This was possibly because PC concentration was still too high to allow a loss of carotenoids from the fat depots.

Brief Communication: Effect of lipids on ram spermatozoal motility - Upreti GC; Hicks K; Oliver JE; Briggs RM; Duganzich DM; Smith JF (Proceedings of the New Zealand Society of Animal Production, 1996)
Lipids from egg yolk, milk and coconut were toxic to ram spermatozoal motility. The toxicity of egg yolk lipid was associated with the neutral lipid fraction. Motility was prolonged in the presence of coconut lipid.

Brief Communication: Effects of milk stasis and feed withdrawal on capillary exchange capacity in the goat mammary gland - Farr VC; Davis SR; Prosser CG (Proceedings of the New Zealand Society of Animal Production, 1996)
The lactating mammary gland is critically dependent upon the provision of nutrients and hormonal stimuli from the blood to sustain milk synthesis. This is reflected in the high correlation between mammary arterial blood flow (F) and milk yield (MY). During established lactation in goats, frequent milking with oxytocin results in a higher blood flow to the mammary gland (Prosser and Davis, 1992). Conversely, MY and F decrease during both milk stasis (Stelwagen et al. 1994) and feed withdrawal (Davis and Collier, 1985). It has yet to be determined whether these decreases in the blood supply cause the decreases in MY or are as a result of a decrease in demand for blood by the secretory tissue.

Brief Communication: The effect of inorganic ions on ram sperm motility using Computer Assisted Sperm Analysis (CASA) - Briggs RM; Upreti GC; Smith JF; Duganzich DM (Proceedings of the New Zealand Society of Animal Production, 1996)
The role of specific inorganic ions in the maintenance of ram sperm motility in a chemically defined ram semen diluent (RSD-1) was examined. A preliminary experiment identified that magnesium was required to maintain motility. Significant treatment and incubation effects were observed for all motility parameters (P<.05). RSD-1 (treatment T1) was modified to provide a series of treatments. Effects measured were the substitution of MgCl2 (T2) or MgSO4 (T3) and the elimination of KH2PO4 (T4) or NaHCO3 (T5). A total of 10 ejaculates were analysed using the Hobson Sperm Tracker (HST) over a period of 7 days. Semen was cooled to 15 C after dilution with treatment diluents and reheated to 38 C after 1 hr and 5 days storage. Motility was measured after incubation at 38 C for 0, 24, and 48 hours. Treatments had a significant (P<0.001) effect on the velocity parameters and the percentage of motile sperm. Treatments T4 and T5 had greatest depression in motility parameters with fresh semen while T5 also had an effect with stored sperm. Substitution of the MgSO4 (T3) reduced the velocity parameters in the fresh semen e.g. mean Curvilinear velocity (VCL) values (

Brief Communication: The effect of somatostatin infusion on milk yield of goats - Davis SR; Farr VC; Myung KH; Prosser CG; Spencer GSG (Proceedings of the New Zealand Society of Animal Production, 1996)
Somatostatin is a hormone widely distributed among tissues which, depending upon species, will inhibit growth hormone release from the pituitary gland and modulate the release of insulin from the pancreas (e.g. Davis, 1975; Maglad et al.,1983). The physiological function of somatostatin in rumi-nants is largely unknown. Certainly effects of somatostatin on the function of the gastro-intestinal tract have been reported (Barry et al.,1985). However, somatostatin ap-pears not to modulate basal growth hormone release in ruminants (Davis, 1975).

bST: An assessment of potential response for pasture based dairy farms in New Zealand - Ekanayake PMB; Matthew C; Bailey WC (Proceedings of the New Zealand Society of Animal Production, 1996)
Potential response of lactating dairy cows to bovine somatotropin (bST) was estimated ex ante for 12 geographically distinct pastoral regions of New Zealand. The estimation process was as follows. First, seasonal pasture growth data were collected or, where such data were unavailable, seasonal pasture growth was estimated from published climate data using the GROW model. The UDDER model was then used to generate, from the pasture growth information and average regional stocking rate, seasonal pasture mass profiles for an

The calpain proteolytic system in different types of ovine skeletal muscles and relationship to meat tenderness - Singh K; Dobbie PM; Simmons NJ; Bass JJ; Thomson BC; Speck PA (Proceedings of the New Zealand Society of Animal Production, 1996)
The calpain system is involved in postmortem tenderisation of meat. Muscle type also influences tenderness and aging rate. This study investigated the extent to which differences in the calpain system may account for differences in tenderness. Calpain and calpastatin activities were measured from 12 different ovine muscles. Shear force was determined on muscle aged at 15 C for 1, 2, 3 and 4 days postmortem and ultimate pH measured. Calpastatin,

Calving performance after embryo transfer-induced twinning - a summary of 30 studies - McMillan WH (Proceedings of the New Zealand Society of Animal Production, 1996)
Twin calving in beef cows has been proposed as a strategy to increase the biological as well as economic efficiency of beef production. The aim of this paper is to summarise the calving performance of cows induced to calve twins following embryo transfer using data from 30 published studies. The pooled data shows that 45, 28 and 27% of recipients give birth to either 0, 1 or 2 calves resulting in 82 calves born/100 recipients and 47% of calving cows producing twins. Overall mean embryo survival rate was only 41%. Compared with recipients which received in vitro-produced embryos, a higher proportion of recipients that received either a pair of in vivo-derived embryos or a single such embryo in conjunction with AI were pregnant (60 vs 43%) or produced twin calves (52 vs 39%). In addition, more calves were born (90 vs 60%). Considerable variation exists in all parameters, particularly the proportion of number of calves born.

Characterisation of beef cattle breeding industry structure - Charteris PL; Garrick DJ (Proceedings of the New Zealand Society of Animal Production, 1996)
The structure of the beef cattle industry, from a breeding viewpoint is characterised by registered herds from which bulls are sold to: other registered breeders, commercial beef cattle farmers and dairy farmers. This project characterised New Zealand

A comparison of two methods of castration of post-pubertal beef cattle and their effect on behaviour, growth and ultimate pH - Jago JG; Matthews L; Bass JJ; Knight TW (Proceedings of the New Zealand Society of Animal Production, 1996)
This study aimed to evaluate the effect of surgical and immunocastration of post-pubertal beef cattle on their sexual and aggressive behaviour, growth and meat quality. Forty mixed-breed bulls were assigned to one of four treatments (n = 10): steers (S) castrated at 11 months of age, late castrates (LC) surgically castrated at 17 months of age (Day 1), immunocastrates (I) vaccinated against GnRH at 17 months of age (Day 1) and entire bulls (B). Sexual and aggressive behaviour was monitored at monthly intervals and prior to slaughter, animals were weighed and blood sampled fortnightly. All treatments were slaughtered at 22 months of age after which carcass composition and meat quality (pHu) were assessed. Plasma testosterone concentrations declined to the level of steers by Day 14 for late castrates and by Day 28 for immunocastrates and remained lower than for entire bulls through to slaughter. Entire bulls had a heavier hot carcass weight (HCW) than I, LC and S. Immunocastrates were heavier than LC and S. Treatment had no effect on pHu although late castrates tended to have a higher mean pHu than immunocastrates and steers. From Day 0 to slaughter, rates of sexual and aggressive behaviour declined significantly for bulls, late castrates and immunocastrates to be similar to steers. There was a tendency for bulls to show higher levels of both sexual and aggressive behaviour during lairage.

A comparison of unbred and once-bred lamb production - Johnston JB; Morris ST; Purchas RW; McCutcheon SN; Parker WJ (Proceedings of the New Zealand Society of Animal Production, 1996)
The once-bred lamb (OBL) production system involves mating ewe lambs at 8 months of age to be slaughtered at approximately 15 months of age after rearing a lamb. This study compared the performance of bred ewe lambs (

A computationally feasible test day model with separate first and later lactation genetic effects - Wiggans GR; Goddard ME (Proceedings of the New Zealand Society of Animal Production, 1996)
In a two step analysis test day effects were estimated within herd with adjustment for across herd effects and then the adjusted data were analysed across herd. Genetic effects were defined for each of 10 months in milk within first and later lactation and for milk, fat and protein giving 60 traits. The rank of the genetic (co)variance matrix (G) was reduced to 6 such that G retained the information to evaluate the selection objective. A repeatability model allowed for multiple lactations with each lactation, conceptually, expressing all 60 traits, but missing observations for 30 or more. A canonical transformation was applied to create uncorrelated traits. Missing values were replaced by their expectations at each round. Because of the rank reduction, only 6 canonical traits were solved for. This system should make evaluations more stable by removing biases due to genetic differences in persistency and rate of maturity.

Dairy cattle breeding in New Zealand - Wickham B (Proceedings of the New Zealand Society of Animal Production, 1996)
The New Zealand dairy industry has undertaken a substantial amount of research and development on the economic, genetic, and reproductive aspects of cattle breeding. Much of this research has been conducted within Livestock Improvement and has not been widely published. The purpose of this contract is to bring together a series of papers which provide a summary of the achievements in cattle breeding and identify challenges and directions for the future. They complement the Livestock Improvement lecture by Dr Michel Georges, in which he discusses the use of markers assisted selection as a potential tool to increase rates of genetic gain. The paper by Spelman et al.,reports the results of the first efforts to identify the contribution that this technology can make in New Zealand's dairy cattle breeding schemes.

Dairy cow performance on limpograss (Hemarthria altissima) - Woods PW; Couchman JN; Clark DA (Proceedings of the New Zealand Society of Animal Production, 1996)
Limpograss is a perennial subtropical grass which has the potential to produce a bulk of standing feed (34 t DM/ha/yr) for consumption by cattle during summer. To assess the value of limpograss for lactating dairy cows, two experiments were conducted comparing limpograss and mixed temperate pasture diets. In both experiments a four day adjustment period was allowed before milksolids yield was assessed on three of the following ten days. Forage samples were taken for nutritional value assessment. During March 1994, two groups of six Friesian cows on once a day milking late in lactation were pen fed diets of freshly harvested limpograss (Hemarthria altissima) or temperate pasture at equal intakes of 13.1

Development of fibre and follicle characteristics related to wool bulk in Perendale sheep over the first year of life - Dick JL; Sumner RMW (Proceedings of the New Zealand Society of Animal Production, 1996)
The pattern of wool fibre and follicle development was monitored for 20 Perendale lambs from lines selected for or against wool bulk. There was no significant difference in characteristics associated with wool bulk between selection lines at birth. These characteristics followed a curvilinear pattern of development with most of the change taking place between birth and 14 weeks of age then reaching a plateau by 35 weeks. The different rate of developmental change for each bulk line meant that by 14 weeks the high line had a greater follicle curvature grade, shorter follicle length, shallower follicle depth, more para-meso cortex and a higher fibre curvature. Together fibre curvature, fibre diameter and fibre diameter standard deviation explained around 70% of the variation in hogget wool bulk from 25 weeks of age. From these results it is suggested that the potential of a sheep to produce high bulk wool can be assessed using fibre curvature and fibre diameter from 6 months of age which allows hogget mating and/or early culling to be practised.

Differences in the post mortem kinetics of the calpain system in meat from bulls and steers - Thomson BC; Dobbie PM; Simmons NJ; Singh K; Speck PA (Proceedings of the New Zealand Society of Animal Production, 1996)
This experiment investigated differences in meat tenderness as defined by shear force between bulls and steers, and how these related to differences in the post mortem kinetics of the components of the calpain system. Strip loins (m. longissimus dorsi) from bulls with acceptable (pH < 5.7) ultimate pHs were compared with strip loins from prime steers. Samples were aged for 1, 3, 7, 13, 24, 48 and 72 hours at 15 C. The activities of calpastatin and (

Dynamic programming applied to the dairy cow replacement decision - Crequer JG; McArthur ATG (Proceedings of the New Zealand Society of Animal Production, 1996)
This research addresses the question

The effect of albendazole controlled release capsules and moxidectin injection treatment on faecal egg count and body weight of 18 month old ewes in the autumn - Kempthorne R; Familton AS; McAnulty RW (Proceedings of the New Zealand Society of Animal Production, 1996)
Sixty 18 month old Romney ewes were drenched orally with ivermectin at twice the recommended dose rate (400

Effect of body covers on the liveweight gain of heifer replacement calves and yearlings, and the liveweight gain and milksolids production of dairy cows - MacDonald KA; Penno JW (Proceedings of the New Zealand Society of Animal Production, 1996)
Body covers are used on dairy stock in an attempt to increase production by reducing the amount of energy required for thermoregulation. Experiments were undertaken to determine the production response to covering calves, yearlings and cows at several sites representing different climatic conditions of the dairying districts of New Zealand. Calves (n=435) were randomly allocated to covered or uncovered treatments on 5 farms in 1993 (n=249) using PVC covers and 4 farms in 1994 (n=186) using Jute covers. Calves were covered for approximately 6 weeks prior to weaning. The difference in total liveweight gain between the covered and uncovered calves within farms ranged from +2.6 kg (

Effect of calving liveweight on milk yield and composition and daily dry matter intake in Friesian and Jersey heifers - Mackle TR; Parr CR; Stakelum GK; Bryant AM; Macmillan KL; Auldist MJ (Proceedings of the New Zealand Society of Animal Production, 1996)
Milk yield and composition were measured weekly throughout lactation, and daily dry matter intake (DMI) on 7 occasions, for Friesian (n=16) and Jersey (n=16) heifers calving at either high (H) or low (L) liveweights. During the 8 weeks pre-partum, heifers were fed to achieve calving liveweights of 404 (H Friesian), 354 (L Friesian), 334 (H Jersey) and 277 (L Jersey) kg. All heifers were fully fed on pasture as one group for the whole of lactation. Calving liveweight had no effect on average DMI over the season. Average DMI was higher for Friesians than Jerseys while average liveweight- corrected DMI was slightly greater for Jersey than Friesians. Average daily milk yields and yields of lactose were lower for L than H heifers. Solids- corrected milk yields and yields of milkfat and protein were unaffected by calving liveweight, but milkfat % and protein % were higher for L than H heifers. The Friesians had higher milk yields, and yields of protein and lactose, but lower milkfat % and protein % than Jerseys. No effect of restricted feeding during late pregnancy in heifers was demonstrated on milk solids production in the subsequent lactation.

Effect of feeding turnips to dairy cows grazing limited amounts of pasture in mid to late lactation on milksolids production - Penno JW; Bryant AM; Napper AR; Copeman PJA (Proceedings of the New Zealand Society of Animal Production, 1996)
Three groups of 20 cows were allocated to one of three feeding treatments. A control group was offered only a restricted pasture allowance. Treatments groups were offered pasture and turnips at either 4 or 8 kg DM/cow/day. Cows offered 4 kg DM/cow and 8 kg DM/cow of turnips produced 265 g MS/c/day (

The effect of Fenbendazole on the immune system of lambs - Parish SJ; McFarlane RG; Familton AS; Abell TJ (Proceedings of the New Zealand Society of Animal Production, 1996)
Measurement of lymphocyte blastogenesis and antibody production were used to determine the effect of a benzimidazole anthelmintic on the immune response. Both parasitized and parasite-naive (n=12) lambs, 6 months of age, were treated with fenbendazole (5mg/kgBW) and compared with untreated control animals. All animals (n=24) were given bovine virus diarrhoea (BVD) vaccine the day following anthelmintic treatment. Heparinised blood samples were collected 0,3,7,14 and 21 days after the anthelmintic treatments. The entire treatment regime was repeated at Day 28. No effects on immunity were apparent after the initial dosage with fenbendazole. However, peripheral lymphocytes from lambs (parasitized and parasite-naive) collected 14 days after the second administration of fenbendazole treatment, had significantly lower stimulation indices compared to control animals, when cultured in vitro with concanavalin A (Con A) (P<0.01), phytohaemagglutinin (PHA), and lipopolysacchride (LPS)(P<0.05). In addition, stimulation to Con A was depressed 7 days after the second treatment. The primary and secondary humoral responses to BVD vaccination, as measured by serum neutralisation titre, were similar among groups. The repeated use of anthelmintics from the benzimidazole group may interfere with immune responsiveness in young sheep.

Effect of iodine supplementation on milk iodine concentrations and productivity of dairy cows - Grace ND; Waghorn GC; Mills AR; Death AF (Proceedings of the New Zealand Society of Animal Production, 1996)
Iodine (I) concentrations in New Zealand pastures are low and may be inadequate to meet the I requirements of lactating dairy cows. A trial was undertaken with 400 cows to determine the effects of a single intra-muscular injection of 2000 mg I (in popyseed oil) given at the beginning of lactation on cow performance. The pasture I concentration ranged between 0.17-0.26 mg I/kg DM during of the trial and the supplement increased serum thyroxine (T4) and milk I concentrations for 76 (P<0.05) and 170 (P<0.01) days respectively. Iodine supplementation did not affect milk yield milk composition or number of services per conception. To increase I status and maintain milk I concentrations at or above 40

Effect of lamb shearing on fine wool Merino hogget performance - Newman S-AN; Maddever DC; Sumner RMW (Proceedings of the New Zealand Society of Animal Production, 1996)
The effect on hogget productivity and wool processing performance of shearing Merinos for the first time as lambs was investigated. A flock of 200 fine wool Merino lambs were randomly separated into two lines. One line was shorn as lambs in late summer and both lines were shorn the following spring as hoggets. There were no differences in live weight at hogget shearing or in flystrike incidence and internal parasite levels. Total wool production was greater from the twice shorn hoggets compared to those shorn only once, with the hoggets shorn twice producing about 0.4 kg more wool. However the differences in hogget wool quality, processing and product performance when lamb wool was removed and the extra wool production did not cover the discounted wool values due to shorter wool staple length and the extra costs of shearing. At current price relativities justification for first shearing Merinos as lambs must relate to management advantages pertaining to individual properties.

Effect of nitrogen fertiliser and supplements on pasture production and milksolids yield from dairy farm systems - Penno JW; Bryant AM; MacDonald KA (Proceedings of the New Zealand Society of Animal Production, 1996)
Seven farmlets of 6.48 ha grazed by Friesian cows at stocking rates of either 3.24 or 4.48 cows/ha were used to evaluate the effect of high rates of nitrogen fertiliser (N) and rolled maize grain on milksolids (MS) production. Annual applications of 213 and 379 kg N/ha increased annual net herbage accumulation by 3350 and 4650 kg DM/ha respectively. At 3.24 cows/ha extra DM resulted in a three fold increase in pasture conservation, providing silage for use in late lactation, and increasing production by 72 kg MS/cow. The extra pasture reduced the amount of supplement required at 4.48 cows/ha. Offering supplementary feed when cows were over grazing or being under fed resulted in an extra 43g milkfat and 47g milk protein/kg DM at the low stocking rate and 45g milkfat and 36g milk protein/kg DM at the high stocking rate. Responses to extra feed were greatest when used to extend lactation. Increased stocking rates will be necessary to maintain pasture utilisation when large amounts of extra feed are introduced.

Effect of selection for early lambing on the testicular diameter of the male offspring - Smith JF; Parr J; Duganzich DM (Proceedings of the New Zealand Society of Animal Production, 1996)
Testicular size has been linked to reproductive efficiency and changes in testicular size could provide an early indicator for the choice of ram lambs to be used in flocks selecting for out-of-season breeding ability. For 3 years, 20 ram lambs from each of the BV(DL)-ve (earlier lambing) and BV(DL)+ve (later lambing) flocks at Ruakura were monitored for testicular diameter (TD) and liveweight (LWT) from weaning until November the following year. In 1991 and 1992, BV(DL) class and season of birth were confounded while in 1993 both BV(DL) classes were represented in both seasons of birth (Autumn and Spring). At the same age Autumn born BV(DL)-ve rams had larger (P<0.05) TD than did Spring born BV(DL)+ve rams in all years. For the 1993 born lambs, the shape of the TD growth curve was different for each BV(DL) x season of birth sub-class (P<0.001). However, at any single age point the within sub- class variation in TD (rsd = 4.6 mm) was such that no meaningful selection for BV(DL) could be made within rams for that season of birth. Liveweight interacted with TD and this effect was also influenced by the season of birth. These data indicate that while TD is influenced by season of birth, the difference in TD between ram lambs of divergent BV(DL; selection for out- of-season breeding ability) was not sufficient for TD to be a useful parameter for early selection.

The effect of shearing by cover comb or blades on the resistance of sheep to cold, windy and wet conditions - Burnham DL; Holmes CW; Morris ST; Parker WJ; Kidd RI (Proceedings of the New Zealand Society of Animal Production, 1996)
Four pairs (total 8 sheep) of Romney mixed-age ewes were housed indoors and fed chaffed lucerne hay at a level equivalent to 1.2 times maintenance. Oxygen consumption was measured in two open circuit calorimeter chambers on days -3, -2, 0, 2, 6 and 10 with day 0 being day of shearing. On each measurement day, oxygen consumption was measured under two sets of climatic conditions (cold plus wind, followed by cold plus wind plus rain). Differences in live weight, fleece weight and liveweight gain of the ewes were not statistically significant. The difference in the rate of oxygen consumption (litres/kg0.75/hour) between cover comb and blade shorn-sheep was not significant during the cold+wind conditions. However, when

Effect of Streptococcus uberis infection on milk characteristics of individual quarters - Lacy-Hulbert SJ; Woolford MW; Nicholas G; Stelwagen K (Proceedings of the New Zealand Society of Animal Production, 1996)
Composite 24 h milk samples were collected for detailed milk analysis from each quarter of ten cows known to be free of intramammary infection. Milk yield and concentration of lactose and serum albumin (BSA) were significantly higher (P<0.001), and chloride ions significantly lower (P<0.001), in hind compared with fore quarters. Four cows developed clinical intramammary infection when subsequently challenged in the left hind quarter with Streptococcus uberis. For all parameters measured, i.e. protein, lactose, somatic cell count (SCC), BSA and immunoglobulins (IgG), milk from the infected quarter differed significantly from the uninfected quarters. No effect of infection was observed in quarters adjacent to the infected quarter, except for SCC, which increased significantly (P<0.001) in the uninfected hind quarter. Milk proteolytic activity in the infected quarter increased significantly (P<0.001) due to increased conversion of plasmin to plasminogen.

Effect of wool length and season of shearing on the propensity of Romney, Coopworth and Perendale wool to yellow - Reid TC; Sumner RMW; Sedcole JR; Botica KJ (Proceedings of the New Zealand Society of Animal Production, 1996)
Propensity of wool to yellow is defined as its yellowness after incubation for 14 days at 40 C and 100% relative humidity. It was determined for mid-side wool samples from Romney, Coopworth and Perendale ewes shorn in summer and/or winter. All samples had a high propensity to yellow (mean Y-Z after challenge 13.0 SD 3.2). The breed ranking from lowest to highest was Perendale, Romney and Coopworth (12.4, 13.1, 13.6, respectively; SED 0.2). Wool shorn in winter was less susceptible to yellowing than wool shorn in summer (11.7 vs 14.4; SED 0.26) and short wool was less susceptible than long wool (12.0 vs 14.1; SED 0.26). There was a highly significant interaction between wool length and time of shearing. Propensity to yellow of wool sampled at hogget shearing was not a significant predictor of propensity to yellow of the adult fleece wool. The measurement was repeatable between some, but not all, successive shearings of adult ewes. This suggests that the method used may be useful in selecting adults to reduce yellowness by breeding.

Effects of condensed tannins on animal performance in lambs grazing Yorkshire fog (Holcus lanatus) and annual ryegrass (Lolium multiflorum) - Montossi F; Hodgson J; Morris ST; Risso DF (Proceedings of the New Zealand Society of Animal Production, 1996)
A comparative study was undertaken in Uruguay from August to early November 1994 to investigate differences in animal performance between lambs rotationally grazing mixed swards of annual ryegrass (Lolium multiflorum) and white clover (Trifolium repens) or Yorkshire fog (Holcus lanatus) and Trifolium repens. The effects of condensed tannins (CT) on lamb production were assessed by twice daily oral administration of polyethylene glycol to half the lambs on each sward combination. Lambs grazing on Yorkshire fog swards had higher clean wool growth (1470 vs 1280

Effects of feeding silage and extending lactation on the pastoral dairy system - Pinares C; Holmes CW (Proceedings of the New Zealand Society of Animal Production, 1996)
Short lactation length is one of the main reasons for the low milk yield per cow in New Zealand. This experiment used replicated farmlets to measure the effects of extending the lactation, and feeding extra silage on the dairy farm system. On the 4th April 54 lower yielding cows were dried- off and divided into two equal herds (D). The remaining 64 cows were also divided into two equal herds, and milked for another 54 days (M). Each of the four herds was grazed on a self- contained farmlet, at 2.9 cows/ha. D herds received only grazed pasture (16 kg dry matter (DM)/cow/day allowance), while M herds received pasture (30 kg DM/cow/day allowance) plus silage (5.5 kg DM/cow/day). At the end of the experiment the M system produced 57.7 kg milksolids (fat+protein) per cow, but had lower (P<0.05) average pasture cover (by 584 kg DM/ha) and lower (P<0.001) body condition scores (by 0.33/cow) than the D system. Extra milk can be produced from extra days in milk, but the extra feed required must be planned and monitored very carefully, to prevent losses in body condition and pasture cover.

Effects of post-pubertal castration and diet on growth rate and meat quality of bulls - Cosgrove GP; Knight TW; Lambert MG; Death AF (Proceedings of the New Zealand Society of Animal Production, 1996)
By castrating bulls post-puberty and then finishing before slaughter it may be possible to obtain both the higher growth rate of bulls but the meat quality of steers. Of 50 crossbred bulls, 20 were castrated at 10 months-of age (steers) and 20 castrated at 17 months-of age (castrates). One month after the latter castration, all animals commenced a 100 day finishing period and were slaughtered at the end. Ten steers and 10 castrates were fed a diet of 50% barley : 50% silage while the rest grazed brassica crop and pasture. Bulls were 20 kg heavier than steers at post-pubertal castration (388

Effects of potassium on potential difference across the rumen wall and magnesium metabolism in sheep - Wachirapakorn C; Sykes AR; Robson AB (Proceedings of the New Zealand Society of Animal Production, 1996)
Several in vitro studies have indicated that the potential difference (p.d.) across the rumen wall is important for magnesium (Mg) absorption and that increases in p.d. as a result of high rumen potassium (K) concentration may reduce Mg transport. The aim of this work was to provide quantitative data on the relationship between p.d. and Mg absorption in the live animal and on diurnal variation in p.d. Twelve rumen cannulated ewes, weighing 45

Effects of stage of lactation and season on udder development and milk yield in pasture-fed cows - Eichler SJ; McFadden TB (Proceedings of the New Zealand Society of Animal Production, 1996)
Effects of stage of lactation and season on mammary development and milk yield were determined in three herds of lactating Friesian cows (n~25 cows/herd) during June and July 1995. The herds in early, mid or late lactation calved in Apr-95, Jan-95 or Oct-94, respectively. Milk yield, in June, was higher in early and mid than in late lactation (16.1, 15.3 and 11.7 kg/d respectively, P<0.001). In July, yield was highest in early lactation and significantly lower with each successive stage of lactation (14.0, 12.5 and 10.4 kg/d, P<0.02). Yield decreased from June to July (14.4 to 12.3 kg/day, P<0.001) under increasingly severe nutritional/environmental influences. Udder capacity was higher in early and mid lactation than in late (16.1, 16.2 and 14.3 L, P=0.07), and decreased 18% from June to July (17.1 to 14.0 L, P<0.001). These results suggest that loss of mammary capacity is an important cause of declining milk production due to stage of lactation and season.

Estimation of lactation yield from repeated measures of test day yields - Johnson DL (Proceedings of the New Zealand Society of Animal Production, 1996)
Test day production records were combined into a measure of lactation yield for the purposes of genetic evaluation of lactation production in dairy cattle. The lactation yield estimation adjusts for test day environment, standardises lactation length, takes account of culling and weights test day records according to number of tests, stage of lactation at test and intervals between tests. Any combination of tests can be used allowing for inclusion of records in progress or incomplete lactation in genetic evaluation.

Evaluation of milk EPDs in Angus dams with actual milk production and calf weaning weights - Worrell MA; Thompson CE; Grimes LW; Skelley GC; Williams RH (Proceedings of the New Zealand Society of Animal Production, 1996)
Evaluation of milk EPDs in Angus dams with actual milk production and calf weaning weights written By: Worrell MA, Thompson CE, Grimes LW, Skelley GC, Williams RH

Evaluation of the Cornell Net Carbohydrate and Protein System for dairy cows fed pasture-based diets - Kolver ES; Barry MC; Penno JW; Muller LD (Proceedings of the New Zealand Society of Animal Production, 1996)
This study evaluated the Cornell Net Carbohydrate and Protein System (CNCPS) for dairy cattle consuming pasture-based diets. Data was obtained from four grazing, and four indoor pasture feeding experiments (23 dietary treatments) with dairy cattle in New Zealand and the United States. ME requirements for maintenance were adjusted to account for grazing activity. The model gave a reasonably good prediction of changes in condition score (R2=0.79, slope not significantly different from 1), energy balance (R2=0.76, slope not significantly different from 1), blood urea nitrogen (BUN) (R2=0.91, underprediction bias of 0.4%), microbial nitrogen flow (R2=0.83, slope not significantly different from 1), and milk production. The model underpredicted DM intake (R2=0.80, 11% bias), and overpredicted ruminal pH (R2=0.47, 1.8% bias). These results indicate that the CNCPS can be used to make realistic predictions of ruminal fermentation and performance of dairy cows offered good quality pasture.

Ewe maternal behaviour score and lamb growth: Ten years on - O'Connor CE (Proceedings of the New Zealand Society of Animal Production, 1996)
Maternal Behaviour Score (MBS) has previously been positively associated with lamb weaning weight. This study further investigated the effects of MBS and other ewe behaviours on the growth rate of 111 Scottish Blackface lambs to weaning. Four variables which had a significant effect on growth rate in a stepwise regression analysis were: birthweight (p<0.05), pre-lambing and early post-lambing ewe liveweights (p<0.001) and MBS (p<0.05). The relationship between MBS and lamb growth rate was not linear. An increase in MBS from 2 to 3 was associated with the greatest increase (10%) in growth rate. MBS was correlated to the frequency of ewe calling (p<0.01) and ewe head up, alert posture (p<0.01) observed during undisturbed field interactions. These behaviours are used to maintain contact between the ewe and lamb, and are indicators of ewe awareness. Therefore, MBS is a good indicator not only of lamb growth but also of the strength of the pre-weaning ewe-lamb relationship.

Factors influencing induced oestrus in the ewe at the start of the breeding season - Fenton LS; Shackell GH; Ramsay ML; Dodds KG; Reid PJ; McLeod BJ (Proceedings of the New Zealand Society of Animal Production, 1996)
The objectives of this study were to monitor the physiological events associated with decreasing liveweight in Bos indicusheifers and to determine the characteristics which best predicted the onset of nutritional anoestrus. Eleven post-pubertal Brahman heifers received a diet resulting in a liveweight loss of 0.7 kg/day. Changes in ovarian morphology were monitored using daily transrectal ultrasonography. Liveweight was recorded twice weekly. Heifers became anoestrus after 98 ± 9 days, following a decrease in liveweight of 68.6 ± 4.9 kg, equivalent to 21.5 ± 1.5% of initial weight. At this time, maximum diameters of ovulatory follicles and corpora lutea (CL) had decreased by 16.7 ± 3.9% and 23.7 ± 3.1%, respectively. Onset of anoestrus was best predicted by liveweight and maximum diameter of CL when expressed as proportions of initial liveweight and size of CL. The percentage decreases in liveweight and maximum diameter of CL to give a 50% probability of anoestrus were 21.0% (95% confidence interval = (17.7, 27.4)) and 23.0% (16.7, 37.0), respectively.

Faecal nematode egg counts and facial eczema susceptibility in Romneys - Morris CA; Towers NR; Watson TG; Wheeler M; Amyes NC; Hosking BC (Proceedings of the New Zealand Society of Animal Production, 1996)
A study was carried out in two groups of flocks to estimate the relationship between susceptibility to facial eczema (FE) and susceptibility to nematode parasites. Faecal egg count (FEC) data on lambs born in 1989- 92 from 53 sire groups were collected on the Ruakura Romney flocks which have been divergently selected for resistance/susceptibility to FE. In addition, the Romney flocks selected at Rotomahana/Tokanui Stations for resistance/susceptibility to FEC were sampled to provide the converse (i.e. FE data) on lambs born in 1988 and 1989, and representing 43 sires. Faecal samples for FEC were collected from lambs in January and March (separated by an anthelmintic treatment) and the FEC data were analysed using a loge transformation. FE susceptibilities, using the enzyme gamma- glutamyltransferase (GGT) as an indicator, were obtained in the FE flocks at Ruakura after an oral sporidesmin challenge in May, and in the FEC flocks at Tokanui after unintentional field challenge; the GGT data were also analysed using a loge transformation. The weighted average heritabilities of loge GGT and loge (FEC+100) were 0.44

A farm level model to aid decisions regarding the feeding of concentrates to dairy cattle - Neaves PJ; Parker WJ; Holmes CW (Proceedings of the New Zealand Society of Animal Production, 1996)
In recent years dairy farm consultants in New Zealand and Australia have regularly been asked to provide advice to farmers on whether the feeding of concentrates to lactating cows on pasture diets is likely to be economic. The outcome of such a decision is complicated because its effects on milk production, liveweight change, pasture growth and decay, and herd reproductive performance are influenced by variables pertaining to the particular farm and herd involved. Some responses to concentrate inputs are immediate; others occur in the long term. Information on each response variable was integrated into a manual decision support framework to provide a practical decision aid for consultants and farmers. A spreadsheet template was then developed to reduce calculation time and allow a wider range of feed and herd situations to be evaluated. The total economic benefits, and hence breakeven price for concentrates were found to be heavily dependent on the long term moblisation of liveweight gained, utilisation of extra pasture grown and changes in the herd

Frequency distribution of sward height on pastures grazed by cattle alone or co-grazed with sheep - Kitessa SM; Nicol AM (Proceedings of the New Zealand Society of Animal Production, 1996)
Pasture height is increasingly employed in feed planning as a measure of pasture availability. The frequency distribution of pasture height on a ryegrass/white clover pasture grazed by steers has been shown to be a double normal distribution representing

Future directions for meat research and development in New Zealand - Kirton AH; Purchas RW (Proceedings of the New Zealand Society of Animal Production, 1996)
If meat research, from production through to the marketplace, is not adequately funded, then much of the research needed to improve New Zealand

Genetic improvement of meat quality in sheep and cattle - Clarke JN; Morris CA; Speck PA; Upreti GC; Nicoll GB (Proceedings of the New Zealand Society of Animal Production, 1996)
Genetic variations in body composition are apparent as differences among breeds, crosses, selected strains and sire groups. Crossbreeding, use of terminal sires and selection within breeds has tended to concentrate on total meat output rather than quality, despite consistent consumer signals against fat. Evidence suggests that, in males selected using live animal ultrasound measurements of fat and muscle depths, about half of the selection pressure available to improve growth rate should be sacrificed in order to maximise economic response through decrease in carcass fat content. Genetic variations in lean/fat partitioning to different regions and muscles of the carcass, and in traits affecting the wider sensory appeal of cooked meat, are also important to the range and consistency of meat products. Indirect live animal indicators are vital to minimising the high cost of progeny testing. Meat product tenderness is one example. Much of the variation is under the control of the calpain system for which genetic differences have been found among breeds and crosses, related families, selection lines, and in strains segregating for major genes and genetic markers (e.g. calpastatin and the CSSM18 and TGLA122 markers of the callipyge gene in sheep). Decreased post mortem tenderness is associated with decreased proteolytic enzyme activity which in some cases is related to increased lean growth rates in the live animals as well. Between and within muscle variations in actin/myosin interactions, lipid, myoglobin contents and solubilities can also give rise to genetic variations in tenderness, meat flavour, colour and the heat gellation properties of myosin. The biochemical basis of these effects suggests useful indicator traits (e.g. LDH and ICDH enzyme activity associations with fibre type, intra-muscular fat and haem iron contents) which are likely to offer innovative genetic solutions to long-term industry competitiveness.

Genetic parameters for fertility traits in seasonal dairy cattle - Grosshans T; Xu ZZ; Burton LJ; Johnson DL (Proceedings of the New Zealand Society of Animal Production, 1996)
Genetic parameters for female fertility traits in New Zealand dairy cattle have been estimated using a data set of herds participating in the Livestock Improvement Sire Proving Scheme. In total, 66294 records of both pure and crossbred Friesian, Jersey and Ayrshire cows in their first lactation were used. The highest heritability estimates were .134, .058, .037, .037, .029 for age at calving (AC), interval from start of mating (STOM) to first mating (SMFM), interval from STOM to conception (SMCO), pregnancy rate at day 21 or 42 after STOM (PR21) or (PR42), respectively. Low heritabilities were obtained for first mating to conception (FMCO), calving interval (CI) and number of services (NS) (<.017). Genetic correlations between CI and either SMFM or SMCO where high (.920 or .957). Genetic correlation between SMCO and PR21 or PR42 is close to one. Therefore the later three traits are identical from the selection point of view. For AC, genetic and phenotypic correlations with milk production traits were high and unfavourable. Antagonistic genetic correlations also existed between milk yield and the fertility traits and between SMFM, SMCO, FMCO or NS and fat or protein yield. The unfavourable genetic correlations between milk production and fertility traits strongly suggest that fertility performance should be incorporated into the breeding objectives of New Zealand dairy cattle. Based on their heritability estimates, their genetic coefficients of variation and their genetic correlations with production and other fertility traits, it is recommended that SMFM and PR21 (or its more easily obtainable equivalent trait 2-to-24-day non-return rate, 2-24NRR) should be used as selection criteria. In addition, the incidence of use of treatment programmes for overcoming fertility problems, such as induction of calving and anoestrus treatment, should also be incorporated into the selection index.

Growth and carcass characteristics of lambs sired by Texel, Oxford Down and Suffolk rams - Cruickshank GJ; Muir PD; MacLean KS; Goodger TM; Hickson C (Proceedings of the New Zealand Society of Animal Production, 1996)
Three hundred and twelve lambs (160 ram, 152 ewe) sired by Texel (n = 118), Oxford Down (n = 94) and Suffolk (n = 100) rams and out of Romney ewes were grazed at Poukawa Research Station, Hastings, to evaluate comparative growth characteristics and carcass composition. Lambs were sourced from a range of commercial properties and sires. Representative samples from each breed and sex were slaughtered after 84, 112 and 145 days on trial. Fasted liveweight gain were significantly (P<0.001) higher for Suffolk-cross (107 g/d) and Oxford Down-cross (101 g/d) lambs than for Texel-cross lambs (84 g/d). At a constant hot carcass weight (HCW) of 19.2 kg, Texel-cross lambs had a significantly (P<0.01) lower GR (mean 12.0 mm) than Suffolk-cross (14.1 mm) and Oxford Down-cross (13.3 mm) lambs. Carcasses were boned to a commercial specification which maximised the removal of bone and fat. At a carcass weight (CW) of 19.2 kg Texel-cross lambs had a significantly (P<0.001) higher saleable meat yield (SMY; 647 g/kg CW) than Suffolk-cross (634 g/kg) and Oxford Down-cross (629 g/kg) lambs. Texel-cross and Oxford Down-cross lambs had a higher proportion of the SMY in high value cuts (HVC) than Suffolk-cross lambs. At a CW of 19.2 kg Suffolk-cross lambs (395 g HVC/kg SMY) had a lower yield than Texel-cross (402 g/kg; P<0.001) and Oxford Down-cross (400 g/kg; P<0.05) lambs. There was no breed by sex interaction, but ewe lambs yielded a significantly higher proportion of HVC in their SMY (402 v 396 g/kg for ewe and ram lambs respectively, P<0.001). At a CW of 19.2 kg eye muscle area was significantly higher (P<0.001) for Texel-cross lambs (13.5 cm2) than for Suffolk-cross and Oxford Down- cross (both 12.7 cm2) lambs, with no sex differences.

Heart rate response as a measure of stress and welfare in cattle - Jacobson LH; Cook CJ (Proceedings of the New Zealand Society of Animal Production, 1996)
Problems exist in welfare quantification of stressors due to variation in animal responses. A theory, based on adaptation to repeated exposure of a stressor, is proposed for objective assessment of welfare. Cattle of three ages were exposed repeatedly to transport, or aspects of transport. Cattle aged 6 weeks showed a declining tachycardic response to repeated transport (p<0.05). Cattle aged 3-6 months showed no consistent pattern of heart rate response to transport, although bradycardia was observed in some animals. Bradycardia was also observed in 2 year old bulls, the incidence of which declined with repeat exposure to trailer loading. Heart rate decreased over transport in bulls unfamiliar with trailer loading (p<0.05), while no change in heart rate was seen in bulls familiar with a trailer.

Herd-to-herd variations in the properties of milkfat - MacGibbon AKH (Proceedings of the New Zealand Society of Animal Production, 1996)
The solid fat content of milkfat has a major influence on the hardness of butter produced at dairy factories. The aim of this work was to study the variation in the solid fat content of milkfat from thirty herds in the factory collection area on a single day to determine the extent of variation in the milk supply. The solid fat content of the milkfat at 10 C varied from 49.6% to 59.8% between the individual herds. This variation in the milk from different herds is as large as the entire seasonal change observed in the bulked factory silo milk, indicating significant variation in the properties of the milkfat within the factory supply on a single day. Low solid fat content at 10 C was correlated with milk of low fat percent (r = 0.78, P< 0.0005) and high protein-to-fat ratio (r = -0.75, P< 0.0005). Though there was substantial variation in the solid fat content within the breeds, milkfat from Friesian herds had a significantly lower solid fat content than milkfat from Jersey herds (mean

Hormonal induction of oestrus during the early postpartum period and the subsequent effects of nutrition on ovarian activity in dairy heifers - Burke CR; Macmillan KL; Verkerk GA (Proceedings of the New Zealand Society of Animal Production, 1996)
Our working hypothesis was that a significant period of severe underfeeding of dairy heifers during early lactation would not prevent the continuation of normal length oestrous cycles following hormonal induction of oestrus and ovulation in the early postpartum period (pp; 26.0 ( 0.7 d pp). Each of 16 Friesians (F) and 15 Jerseys (J) was treated with a CIDR device for 5 days, with one injection of prostaglandin-F2a the day before device removal and another injection 1.0 mg oestradiol benzoate 24 h after removal. The feed allowances of 8 F and 7 J heifers were reduced over the following 3 oestrous cycles, to a level where live-weights and milk yields were depressed finally by up to 15% and 36%, respectively, compared to fully fed contemporaries. Ovarian ultrasonography and monitoring of concentrations of milk progesterone (mP4) during the 1st (Cyc 1) and 3rd (Cyc 3) oestrous cycles showed that 3 Fs (1 FH and 2 FL) did not respond to initial treatment, and remained anovulatory throughout. Another 3 heifers (2 FL and 1 JL) became anovulatory after an initial positive response. The size of the first dominant follicle (DF1) and concentrations of mP4 were reduced by restricted feeding, but only during Cyc 3. This study has shown that a hormonal treatment can induce oestrus and ovulation in the majority of heifers which have been calved between 20 and 30 days. Subsequent restrictions in feeding level may convert some cycling heifers into an anoestrous state, although most will continue to cycle.

Improving the efficiency of pasture-based dairy production - Lean IJ; Parker WJ; Kellaway RC (Proceedings of the New Zealand Society of Animal Production, 1996)
New Zealand dairy farmers have not achieved the increases in milk production that parallel those of other countries and this has led to a re- evaluation of the opportunities to use feed inputs to complement pasture diets for dairy production. An improved understanding of the chemical composition of pastures, a re-examination of pasture growth dynamics, and recent experimental evidence and farmer experience suggests that there is potential to increase milk production from pasture through strategic inputs of feeds to increase dry matter intake and improve the nutrient balance of the cow

Influence of different proportions of Lotus corniculatus in the diet of lambs on dags, flystrike and animal performance - Leathwick DM; Atkinson DS (Proceedings of the New Zealand Society of Animal Production, 1996)
The relationship was investigated between the number of days each fortnight spent grazing Lotus corniculatus (lotus) or ryegrass/white clover and dags, flystrike and growth rates in lambs. Lambs which grazed lotus for 7 or more days each fortnight had significantly fewer dags (86-113g) and significantly higher live-weight gains (160-104 g/day) than lambs grazed on ryegrass/white clover (154g, P<0.01 and 73g/day, P<0.05 for dags and live- weight gain respectively). Lambs which grazed lotus continuously had significantly higher live-weight gains than lambs which grazed lotus for 7 or less days each fortnight. Flystrike was positively correlated with dags although this was less obvious over time-period 1 when the incidence of flystrike was low. The incidence of flystrike differed significantly between treatment groups ((2 P<0.001), ranging from 36% of lambs struck in the all ryegrass/white clover groups to 7% in the all lotus groups. Wool growth, faecal dry matter content and faecal nematode egg count (FEC) did not differ between treatments. These results confirm the potential of lotus as a tool in the management of dags and flystrike but indicate that lambs will need to be grazed on lotus for 7 or more days each fortnight in order to realise significant benefits.

Influence of level of feeding and stage of lactation on proteolytic activity in bovine milk - Nicholas GD; Prosser CG; Stelwagen K; Mackle TR (Proceedings of the New Zealand Society of Animal Production, 1996)
Using a Latin square cross-over design, twelve sets of identical Friesian or Friesian x Jersey twin cows during spring (early lactation: 42

Magnesium metabolism in sheep subjected to sodium or water loading - Wachirapakorn C; Sykes AR; Robson AB (Proceedings of the New Zealand Society of Animal Production, 1996)
Six rumen-cannulated ewes, averaging 48

Manipulation of gene expression in transgenic mice using ribozymes - L'Huillier PJ; Vilotte JL (Proceedings of the New Zealand Society of Animal Production, 1996)
This study describes the creation and analysis of transgenic mice carrying a ribozyme or RNA enzyme that specifically targets the bovine a- lactalbumin (a-lac) mRNA transcript. Using a MMTV-LTR promoter-based construct, mammary specific high-level expression of a bovine a-lac- targeted ribozyme was obtained in three out of twelve lines of transgenic mice created. When crossed with mice transgenic for the bovine a-lac gene (0.4 mg of a-lac.ml-1 of milk), expression of the ribozyme resulted in a reduction in the levels of the target mRNA to 50% of that observed in the non-ribozyme transgenic littermate controls. This activity was specific to the bovine a-lac transcript as no reduction in the levels of the endogenous murine a-lac mRNA was observed. These results demonstrate the feasibility of ribozyme-mediated down-regulation of highly-expressed transcripts in transgenic animals.

Measurement of cell death by in situ end labelling of ruminant mammary gland tissue - Molenaar AJ; Wilkins RJ; Davis SR (Proceedings of the New Zealand Society of Animal Production, 1996)
Apoptosis was examined by in situ end labelling (ISEL) of DNA in ewe and cow mammary sections representing the cycle of mammary development, lactation and regression. Labelled nuclei, identifying apoptotic dying cells, were found in tissues from all developmental stages. Generally, apoptosis was low in tissue from virgin animals, moderate in 3 and low in 2 week udders from prepartum ewes and mid pregnant cows, moderate to high in udders from 1 week post partum ewe udders, moderate to low in lactating ewes and cows and slightly higher in involuting ewe and cow udders. Apoptosis was also generally higher in alveoli in stasis than in lactating alveoli. A dramatic finding was that there was intense labelling with both 35S and DIG in the lumenal contents of some alveoli in stasis/involution particularly with animals in later lactation. This suggested that there was a significant amount of ragged DNA ends in the lumen of these alveoli.

Measuring body composition by fast neutron activation analysis - Wolff JE; Mitra S; Garrett R; Webb PA (Proceedings of the New Zealand Society of Animal Production, 1996)
The recent availability of a small compact sealed tube neutron generator, incorporating an associated-particle alpha detector, makes it feasible to measure the concentrations of C, N and O in the body with a very low dose of ionising radiation. We describe this new technique and the equipment needed to use it for measuring body composition. Calibration data from a prototype instrument relate the counts of gamma rays due to C, N & O from phantoms to the number of incident 14 MeV neutrons and phantom mass. Applying the technique to one 29 kg Romney wether hogget, we estimated it contained 0.69 kg N, 5.52 kg C and 16.5 kg O. These results indicate that the technique holds promise for monitoring the body composition of paediatric and malnourished patients and for measuring the body composition of young experimental animals such as goats, pigs or sheep.

The metabolic cost of hepatic ammonia detoxification - Greaney KB; Reynolds GW; Ulyatt MJ; MacKenzie DDS; Harris PM (Proceedings of the New Zealand Society of Animal Production, 1996)
The quantity of ammonia removed from portal blood by the ovine liver was measured using four sheep prepared with in-dwelling catheters in the hepatic region and fed either lucerne pellets (L) or white clover (WC) at 900 gDM/day. Following blood sampling, plasma ammonia and oxygen concentrations were determined. The portal ammonia concentration and flow were significantly (P<0.01) affected by the diet (304 and 646

Microbial protein synthesis and milk production in cows offered pasture diets differing in non-structural carbohydrate content - Carruthers VR; Neil PG; Dalley DE (Proceedings of the New Zealand Society of Animal Production, 1996)
The effect on ruminal fermentation and milk production of increasing the proportion of non-structural carbohydrate (NSC) in a pasture diet was investigated in early (Trial 1) and late (Trial 2) lactation. Twenty four cows in Trial 1 and 15 cows in Trial 2 were offered pasture (P), 85% P plus 15% protein/NSC mixture (PR), and P+10% (Trial 1) or P+15% (Trial 2) NSC (PE) in a latin square design. All diets were isonitrogenous and P and PR were isoenergetic. PE but not PR increased microbial protein synthesis and decreased rumen ammonia and milk urea levels compared to P in both trials. In Trial 1, neither PE nor PR increased milk yield or milk solids output compared to P. Nitrogen but not dry matter digestibility was reduced on PR and PE compared to P. Ruminal degradation of casein, but not of pasture, was increased on PR and PE compared to P. In Trial 2 the milk yields of cows offered PE and PR were greater than those offered P, and greater on PE than PR. Increasing the ratio of carbohydrate to protein was more effective in improving nitrogen utilisation in the rumen than was increasing the proportion of NSC.

Milk cortisol concentrations as an indicator of stress in lactating dairy cows - Verkerk GA; Phipps AM; Matthews LR (Proceedings of the New Zealand Society of Animal Production, 1996)
The aim of this study was to compare cortisol concentrations in plasma (PCC) and milk (MCC) following administration of exogenous ACTH1-24 or activation of the hypothalamo-pituitary-adrenal axis by a stressor (transport) in cows. Fifteen cows in mid-lactation were assigned to treatments with ACTH1-24 (0.05 mg Synacthen

Milk production from pastures and pasture silage with different levels of endophyte infection - Clark DA; Thom ER; Waugh CD (Proceedings of the New Zealand Society of Animal Production, 1996)
Perennial ryegrass (Lolium perenne L.) pastures in New Zealand contain the fungal endophyte (Acremonium lolii). This association produces a range of toxins; some, such as lolitrem B and ergovaline have been associated with ryegrass staggers, decreased serum prolactin, heat stress and decreased milk yield. Grazing trials with lactating cows have given equivocal results in terms of milksolids yield. Two experiments examined the effects on autumn milk production of supplementing cows grazing pasture with grass and grass/clover silages containing different endophyte concentrations on autumn milk production. Forty cows were used in a 2 x 2 factorial experiment with low (L) and high (H) levels of endophyte in both pasture and silage. In Experiment 1 (28 March - 6 April 1995) cows were grazing clover free pastures and supplemented with either L or H endophyte grass silage. In Experiment 2 (7-12 April 1995) cows were grazing pastures containing about 17-25% white clover and supplemented with either L or H endophyte grass/clover silage. At the first milk sampling three days after treatments started in Experiment 1, milk yield from cows given L pastures was 6.9% higher than from those grazing H endophyte pastures (P=0.006), and 4.1% more when L rather than H endophyte silages were given (P=0.10). These effects were additive so the cows fed L endophyte silage and L endophyte pasture produced 11.3% more than those fed H silage and H pasture (P=0.002). The effect of pasture endophyte on milk yield was still evident after seven and ten days of treatment, with 10.3% more milk from L than from H endophyte pastures (P=0.01). Milk protein yields paralleled milk yields after seven and ten days but there was an endophyte x silage interaction (P=0.05) for milkfat yield and protein and fat yields were not effected by treatment. In Experiment 2 when clover was included in the diet there were no significant effects from either pasture or silage endophyte status on any milk yield components. A comparison of milksolids yield from Experiment 1 and Experiment 2 shows that changing to diets containing white clover increased milksolids by 6.4, 13.9 and 21.9% for the L/L, L/H and H/L pasture/silage combinations, respectively, but only increased milksolids by 2.7% for the H/H pasture/silage combination. We conclude that endophyte in both pasture and pasture silage can have a transitory effect on milk and protein yield during the autumn and the nutritional benefits of white clover for increasing milksolids was much reduced by endophyte in both pasture and silage diets.

Nitrogen application to dairy pasture - the effect of rate and timing of spring nitrogen applications on the concentration of pasture nutrients - Moller S; Edwards NJ; Parker WJ; Hodgson J; Wilson GF (Proceedings of the New Zealand Society of Animal Production, 1996)
Nitrogen (N) fertiliser was applied to ryegrass/white clover dairy pasture in late winter/early spring. Four rates of N (0, 20, 40, 80 kg N as urea) were applied to pregrazed and premown pasture with a residual herbage mass of 1000 kgDM/ha-1 (stubble height of 1.5 cm). Samples were collected from separate 2m2 plots 2, 4, 6 and 8 weeks after N application to detect nutrient changes over time from N appli

Oestrogenic effects on in vitro co-culture of mammary explants and epithelial cells - Ellis S; McFadden TB; Akers RM (Proceedings of the New Zealand Society of Animal Production, 1996)
Mechanisms of oestrogen stimulation of mammary development were examined using ewe lambs treated with oestradiol (0.1mg/kg BW/day for 7 days; n=5) or controls (n=5). Mammary explants were incubated with [3H]- thymidine to determine effects of oestrogen on epithelial cell proliferation. Also, explants of mammary stroma and parenchyma were co-cultured with a mammary epithelial cell line (MAC-T) to determine the ability of the explants to stimulate MAC-T growth. Oestrogen increased proliferation of ewe mammary epithelial cells (P < 0.02). In co-cultures, addition of mammary explants increased growth of MAC-T cells (P < 0.01), but there was no effect or interaction of tissue type (stroma vs. parenchyma) or oestrogen (P > 0.10). Proliferation of mammary explants was negatively correlated with growth of MAC-T cells in co-cultures (r = -0.41; P < 0.07). These results confirm the importance of oestrogen and mammary stroma in regulating mammary epithelial proliferation but fail to show a requirement for mammary stroma to mediate oestrogenic effects on epithelial cells.

Optimising of the challenge test for the susceptibility of wool to yellow discolouration - Aliaga JL; Sanderson RH; Maher AP; Reid TC (Proceedings of the New Zealand Society of Animal Production, 1996)
The pattern of wool fibre and follicle development was monitored for 20 Perendale lambs from lines selected for or against wool bulk. There was no significant difference in characteristics associated with wool bulk between selection lines at birth. These characteristics followed a curvilinear pattern of development with most of the change taking place between birth and 14 weeks of age then reaching a plateau by 35 weeks. The different rate of developmental change for each bulk line meant that by 14 weeks the high line had a greater follicle curvature grade, shorter follicle length, shallower follicle depth, more para-meso cortex and a higher fibre curvature. Together fibre curvature, fibre diameter and fibre diameter standard deviation explained around 70% of the variation in hogget wool bulk from 25 weeks of age. From these results it is suggested that the potential of a sheep to producehigh bulk wool can be assessed using fibre curvature and fibre diameter from 6 months of age which allows hogget mating and/or early culling to be practised.

Ovarian follicle development in the red deer hind - McLeod BJ; Meikle LM; Heath DA; McNatty KP; Fisher MW; Whaanga AJ (Proceedings of the New Zealand Society of Animal Production, 1996)
Ovaries were recovered either 0, 12, 24 or 36 hours or 10 days after CIDR withdrawal, from 25 hinds in which oestrus had been synchronised. All follicles > 2 mm diameter were dissected free of stromal tissue and their health assessed on the basis of oocyte and theca condition, follicular fluid oestradiol content, granulosa cell numbers and oestradiol synthesis. Hinds had an average of 26.6 + 3.45 follicles > 2 mm, of which about half were healthy and 1-3 were oestrogenic. Every animal had at least 1 healthy follicle > 7.5 mm diameter. Over the follicular phase, the percentage of healthy follicles ranged from 46-66%, but this did not change significantly with time. Neither did the mean diameter of the largest oestrogenic follicle change over the follicular phase. In summary, the total number of antral follicles varied widely, but every hind had at least one large healthy follicle present, irrespective of stage of the oestrous cycle.

Partial failure of multiple ovulations - a question of uterine efficiency or embryo quality? - McMillan WH (Proceedings of the New Zealand Society of Animal Production, 1996)
Amongst individuals that produce multiple ovulations, and conceive, a variable proportion fail to deliver all potential offspring at term. This source of reproductive inefficiency has been termed partial failure of multiple ovulation (PFMO). In the case of twin ovulators, PFMO is manifest as single births. Most reports in the literature have attributed PFMO to uterine capacity or efficiency factors. An alternative model is proposed, in which it is assumed that a given reproductive outcome is determined by independent binomial effects of embryos and uterine/maternal factors. Using this model, it can be demonstrated that PFMO in twin ovulators can only occur because one of the two embryos is not competent to survive - that is, the uterine/maternal component plays no role in determining variation in PFMO. It follows that in pregnant farm animals with twin ovulations 100% twin births is possible, but is only constrained by low embryo quality. All published data examined to date in sheep cattle and goats are consistent with this alternative model.

Patterns of oestrus vary with different forms of synchrony - Macmillan KL; Taufa VK; Morris GR (Proceedings of the New Zealand Society of Animal Production, 1996)
The original objective of a trial conducted in 3 herds of Friesian heifers was to compare pregnancy rates obtained when each animal was synchronised and then inseminated at about 50 h after removal of a subcutaneous ear implant (CrestarTM) or an intravaginal device (GenermateTM). Because most of the heifers in the CrestarTM group were in oestrus before any of the herdmates treated with the GenermateTM system, the CrestarTM treated heifers were inseminated at either 28 h or 50 h after implant removal. Over the 3 herds, 64% of 153 heifers treated with Crestar were in oestrus by 28 h after implant removal compared to 7% of their GenermateTM treated (n=155) herdmates (P<0.01). The average pregnancy rate to first insemination of 56.3% was similar for both synchrony treatments, and for the two insemination times in CrestarTM treated heifers. The earlier onset of oestrus in heifers treated using the CrestarTM system was possibly associated either with persistent and dominant ovarian follicles, or to the injected oestradiol valerate producing behavioural symptoms of oestrus. Nonetheless, inseminating heifers with a shortened interval to oestrus at 28 h rather than 50 h after implant removal may avoid reductions in pregnancy rate which occur with inseminations made after the end of oestrus, or with heifers which ovulate a persistent dominant follicle.

Perspectives for marker assisted selection in dairy cattle breeding - Livestock Improvement Corporation Lecture - Georges M (Proceedings of the New Zealand Society of Animal Production, 1996)
Animal breeders have been manipulating genes for cen-turies, in the sense that by selecting the best performing individuals as the parents for the next generation, they have increased the frequency of favourable alleles and concomi-tantly decreased the frequency of unfavourable alleles at genetic loci influencing the traits of interest. With the intro-duction, in the fifties, of complex biometrical methods to estimate breeding values from own performances and per-formances of relatives, so-called “mass selection” has ma-tured into an extremely powerful methodology. Modern breeding programs are largely responsible for the dramatic increase in the efficiency of livestock production that society has witnessed during the second half of this century.

Plasma carotenoid concentrations early in life can be used as a selection criterion for fat colour in heifers - Death AF; Knight TW; Purchas RW; Morris ST; Burnham DL (Proceedings of the New Zealand Society of Animal Production, 1996)
Plasma carotenoid (PC) concentrations were measured at 2-5 month intervals in 20 Hereford x Jersey (HJ) and 20 Hereford x Friesian (HF) once bred heifers from 10-35 months-of-age. Half of the heifers were slaughtered at 31 months-of-age and the rest at 35 months-of-age. The colour of the subcutaneous and intermuscular fat was measured using a chromameter and c* values were calculated. Subcutaneous and intermuscular fats in HJ heifers were yellower (i.e. they had higher c* values) than in HF heifers. Regression equations that included breed, date of slaughter and PC concentrations at 10-12 months-of-age, accounted for 56% of the variation in c* values for subcutaneous fat and 40% of the variation in c* values for intermuscular fat (P<0.001).

Postmortem changes in pH and shear force in three commercial bull beef cuts - Thomson BC; Dobbie PM; Singh K; Speck PA (Proceedings of the New Zealand Society of Animal Production, 1996)
This experiment investigated the differences between fillet, strip loin and rump cuts obtained from carcasses of pasture-fed bulls. Four samples of each cut were collected on two different occasions and aged at 15 C for 2, 24, 48 ,72 and 120 hours. The pH of the fillet and rump cuts did not change post-slaughter. The pH of the strip loin was higher at slaughter but declined over time and by 48 hrs post-slaughter there were no differences in the pH value of the three cuts. Shear force was determined using a MIRINZ tenderometer. The fillet had the lowest shear force and the rump cut had the highest. There were no differences in the activities of the components of the calpain system at 2 hours post-slaughter. These results suggest that the differences in meat quality and particularly ultimate tenderness, between the three cuts were not due to differences in the activities of the components of the calpain system or pH

Potential for profitable use of DNA markers in the New Zealand Dairy Industry - Garrick DJ; Spelman RJ (Proceedings of the New Zealand Society of Animal Production, 1996)
Annual genetic advance in merit of dairy cattle can be assessed from selection in four pathways: Bulls to breed Bulls (BB); Cows to breed Bulls (CB); Bulls to breed Cows (BC); and Cows to breed Cows. It is usually assumed that breeding merit is determined by actions of a very large number of genes, each having a small effect (infinitesimal model of inheritance). In practice, the number may be finite, with a few genes (known as QTLs) having large effects. DNA technologies allow young animals to be tested for particular QTLs using markers. Benefits of marker assisted selection were calculated for one additive QTL over a range of sizes (allele values of 0.25, 0.38, or 0.5 genetic s.d.) and initial gene frequencies (0.01, 0.10, 0.35). Testing was conducted in the BB, BC and CB pathways. Strategies were compared using the Net Present Value of the stream of productive benefits less costs for a 30 year horizon, assuming one genetic s.d. is worth $160. Superior rates of advance were sometimes achieved at greater cost than benefits. At a cost of $10 per genotype assessment it was never profitable to genotype small QTLs. The largest QTL could be profitably used to screen young bulls before progeny testing except at the lowest starting frequency. In some circumstances, selection for a QTL resulted in improved medium term response but reduced long-term response. Knowledge of the size and frequency of QTLs and a pre-defined time horizon will be essential to discriminate between profitable and costly applications of this technology.

Predicting the onset of nutritional anoestrus in Brahman heifers - Rhodes FM (Proceedings of the New Zealand Society of Animal Production, 1996)
The objectives of this study were to monitor the physiological events associated with decreasing liveweight in Bos indicus heifers and to determine the characteristics which best predicted the onset of nutritional anoestrus. Eleven post-pubertal Brahman heifers received a diet resulting in a liveweight loss of 0.7 kg/day. Changes in ovarian morphology were monitored using daily transrectal ultrasonography. Liveweight was recorded twice weekly. Heifers became anoestrus after 98

Prediction of carcass tissue weight in vivo using live weight, ultrasound or X-ray CT measurements - Young MJ; Nsoso SJ; Logan CM; Beatson PR (Proceedings of the New Zealand Society of Animal Production, 1996)
Twenty-one Dorset Down ewe hoggets (49.4kg body weight, 9months old) were scanned by ultrasound and X-ray computer tomography (CT). Total carcass tissue (fat, muscle and bone) weights were assessed by the Cavalieri procedure from 16-18 CT slices per animal. Additional CT slices were taken at four anatomical reference sites; 7th thoracic (TV7), 2nd lumbar and 5th lumbar vertebrae (LV5), and mid-shaft of the femur. Subcutaneous fat depth and muscle depth were assessed over the last rib using ultrasound. Body weight, ultrasound measurements and reference slice carcass tissue areas were used to predict total carcass tissue weights by multiple regression techniques. In combination with BW, single CT slices predicted tissue weight more accurately than ultrasound measurements with BW for fat (R2=72-84% vs. 63%) but not for muscle (R2=79-87% vs. 83%) or bone (R2=62-66% vs. 65%). The best combination of two CT slices was TV7 & LV5. In combination with BW these improved prediction accuracy further (fat, R2=92%, muscle, R2=91%, bone, R2=71%). It is possible that data from a single CT slice predict carcass tissue weight less accurately than expected due to anatomical registration errors despite CT producing better quality images than ultrasound. These errors are attributed to scanning protocol constraints for CT equipment. Two or more CT slices need to be scanned in order to predict tissue weight more accurately than ultrasound.

Processing for meat quality - Chrystall BB; Daly CC (Proceedings of the New Zealand Society of Animal Production, 1996)
The factors which constitute quality of meat will vary according to its end use. In this sense, quality can be defined as

Profitability of rotational crossbreeding programmes in commercial dairy herds - Lopez-Villalobos N; Garrick DJ (Proceedings of the New Zealand Society of Animal Production, 1996)
Dairy farm profitability can be increased through the use of superior cows in the lactating herd. Genetic superiority is determined by additive genetic effects and heterosis (present in crossbred animals). Profitability is the difference between income (sale of milk, bobby and salvage animals) and costs (related to the number of cows in the herd and the land area farmed). At comparable production, bigger cows consume more feed reducing their profitability per unit feed consumed. Previous studies have identified the high productivity of first-cross cows comprising Holstein- Friesian (F) and Jersey (J) breeds. In a self-replacing herd, first-cross (F1) animals will not be continuously available unless some straightbred animals are maintained. One approach for exploiting heterosis in a self-replacing herd, is to make use of rotational crossbreeding. This paper reports profitabilities of some rotational crossbreeding programs in comparison to farming straightbred dairy animals. A model was used to estimate on an annual basis, the nutritional, biological and economic performance of whole herds consuming 12,000 kg dry matter per ha. Expected performances for straight- and cross-bred cows comprising F, J and Ayrshire (A) breeds, were obtained using estimates of breed and heterosis effects derived from Livestock Improvement

Progress on genetic studies of resilience to nematode parasites in sheep - Morris CA; Bisset SA (Proceedings of the New Zealand Society of Animal Production, 1996)
Recent studies on 3- to 7-month-old lambs have shown that there is genetic variation in the ability to withstand the effects of roundworm challenge and thus maintain acceptable performance (high growth, low dags) when left undrenched for extended periods. This trait is generally referred to as resilience. The heritability of resilience has proved to be low (three years

Prospects for overcoming the physiological limits of dairy cow fertility - Vishwanath R; Xu ZZ; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 1996)
Conception rates to a single first insemination in cycling dairy cows often range between 55% and 75% . This paper outlines the physiological processes that define this outcome and where possible gains could be made. While herd management issues do influence the outcome of a reproduction progamme quite significantly, the main impetus of this review is to identify some opportunities that could raise the threshold level of fertility in New Zealand dairy herds.

Proteases and meat quality - Bickerstaffe R (Proceedings of the New Zealand Society of Animal Production, 1996)
Consumers judge the quality of meat at the point of sale on colour, visible fat content and odour. However, on eating meat, characteristics such as juiciness, flavour and texture also assume importance. Supermarket surveys of customer preferences have indicated that tenderness is the single most important meat quality characteristic that in-fluences whether consumers are repeat buyers. In New Zealand, the industry standard for tenderness is that shear force must be less than 11 kg F for exported meat. The meat industry recognises, however, that 11 kg F is the upper limit for shear force and that for discerning markets, tenderness values of <5 kg F are required if the markets are to be retained or improved.

Quality Meats From The NZ Beef And Sheep Industries - Consistent quality meat products - Speck PA; Kirton AH; Clarke JN (Proceedings of the New Zealand Society of Animal Production, 1996)
Meat quality has different definitions for different people and in different countries, depending on their posi-tion in the value chain. However, the consumer who repre-sents the endpoint of the chain has clearly signaled inconsistent quality of meat as a major consideration in the declining purchases of red meat.

Reducing animal numbers in experiments - Chamove AS; Edwards HP (Proceedings of the New Zealand Society of Animal Production, 1996)
Plasma carotenoid (PC) concentrations were measured at 2-5 month intervals in 20 Hereford x Jersey (HJ) and 20 Hereford x Friesian (HF) once bred heifers from 10-35 months-of-age. Half of the heifers were slaughtered at 31 months-of-age and the rest at 35 months-of-age. The colour of the subcutaneous and intermuscular fat was measured using a chromameter and c* values were calculated. Subcutaneous and intermuscular fats in HJ heifers were yellower (i.e. they had higher c* values) than in HF heifers. Regression equations that included breed, date of slaughter and PC concentrations at 10-12 months-of-age, accounted for 56% of the variation in c* values for subcutaneous fat and 40% of the variation in c* values for intermuscular fat (P<0.001).

Reduction in SCC and colostrum levels in milk after calving - Lacy-Hulbert SJ; Malcolm DB; Copeman PJA; Woolford MW; Franks R (Proceedings of the New Zealand Society of Animal Production, 1996)
Somatic cell count (SCC) and immunoglobulin G1 (IgG1) content were determined in mammary secretions of 15 Friesian x Jersey cows and 5 heifers at each milking for 10 d following natural calving. Milk yields for cows on d 1 were 20.2 l/d, declined sharply on d 2 to 14.4 l/d, then increased slightly, reaching 17.9 l/d by d 10. In contrast, heifer milk yields were low on d 1 (6.6 l/d) but increased steadily to 11.9 l/d by d 10. The SCC and IgG1 levels were extremely high on d 1 (1.50 x106 cells/ml and 24.0 g/l IgG1) but declined rapidly within 48 h of calving. Average SCC and IgG1 reduced below the penalty levels by d 4 for cows, and d 5 for heifers, confirming that milk should be withheld from the bulk tank for 4 d and 5 d after calving for cows and heifers respectively. Individual cows may exceed these levels for short periods.

Relationships between adult liveweights and velvet weights in farmed Red deer - Garrick DJ; Van Den Berg GHJ (Proceedings of the New Zealand Society of Animal Production, 1996)
Deer farmers with velvetting herds are interested in: selection of stags for superior lifetime performance; selection of stags and hinds to produce improved sons; and management of the stag herd to increase returns from velvet. Knowledge of genetic and phenotypic relationships between weights of velvet harvested at different ages and between liveweights and velvet weights will allow benefits from selection and some management practices to be quantified. This paper reports estimates of these relationships from a study involving some 2,021 stags representing 92 sire progeny groups distributed over five farms. Heritability estimates for velvet weight at successive ages from 2 to 8 year old stags ranged from 0.43 to 0.85. The average estimated genetic correlation between velvet weights in successive years was 0.97 but declined to 0.75 as the number of years between harvests increased. Phenotypic correlations were consistently lower than genetic correlations. Treating log- transformed velvet weight as a repeatable trait resulted in an estimated heritability of 0.36 with a repeatability of 0.64 and s.d. of 0.11 (log scale). Average velvet production in kg (Y) can be predicted from age in years (X) from the following equation: log10(Y) = -0.37 + 0.33*X - 0.044*X2 + 0.002*X3 Within a cohort of stags of the same age, heavier stags produced more velvet, with an average genetic correlation of 0.74 and phenotypic correlation 0.44. The genetic correlation between liveweight of hinds at 2 years of age and velvet weight at various ages averaged 0.5. Comparing different cohorts of stags of the same age, there was no relationship between average liveweights and average velvet weights. As stags aged, the average weights of velvet and liveweight increased. Describing velvet weight in kg (Y) as a non-linear function of weight in kg (X) the allometric equation was Y = 0.21*X1.4, indicating velvet weight is later maturing than liveweight.

Repeatabilities of blood plasma metabolites and their associations with leanness in genotypes showing a wide divergence in carcass composition - Clarke JN; Binnie DB; Dobbie JL; Jones KR; Mowat CM; Purchas RW; Uljee AE (Proceedings of the New Zealand Society of Animal Production, 1996)
Strain differences in lean : fat partitioning were typified by a marked contrast in a lean growth index giving equal but opposite emphasis to the weights of protein and fat, in line with previous publications. Strains showed characteristic differences in blood metabolites which did not necessarily reflect genetic variations within a strain and correlated responses to within-breed selection for changes in body composition. High repeatabilities of blood metabolites within a strain were found for pasture-fed lambs aged between 5 and 14 months for samples collected on the same day following overnight fasts of 20 vs 24 hours, but were lower for samples taken from fasted animals at different ages. Between-age within- strain repeatabilities (averaged across two trials) were moderate for plasma urea (0.24) creatinine (0.38) and non-esterified fatty acids (0.18), but low for beta-hydroxybutyrate (0.09). Similar moderate heritability estimates were found for urea and creatinine. Although standard errors were very high for this small dataset based on only 12 sires, estimates for carcass composition were in broad agreement with other more reliable published values. Also in line with other results, sire-progeny variations in urea and beta- hydroxybutyrate were more positively related to carcass protein than carcass fat, while the reverse was true for creatinine. Metabolically contrasting pairs of metabolites showed potentially useful predictive associations with sire- progeny variations in protein:fat partitioning.

Reproductive efficiency in lactating dairy cows - Xu ZZ; Burton LJ (Proceedings of the New Zealand Society of Animal Production, 1996)
Both genetic improvement and milk yield of dairy cows are dependent on a high reproductive performance. Under normal situations, oocyte fertilisation rates following insemination at the appropriate time are high (>90%) and gross genetic defects in embryos are estimated to be around 10%. This means that the biological limit of conception rate should be around 80%. Such a performance has rarely been realised in practice, with 60% being a normal target for lactating cows in New Zealand dairy herds. At a herd level, reproductive performance is best measured by the percentage of cows pregnant within a period after start of the breeding season and this is determined by the combination of submission rate and conception rate. Major factors that affect reproductive performance in New Zealand dairy herds include anoestrus, errors in heat detection, fertilisation failure and embryo mortality. Given adequate nutrition, herd management is undoubtedly the major determinant of reproductive efficiency. The low reproductive efficiency in dairy cows creates a bottleneck to genetic improvement and is a major factor affecting milk production efficiency.

Reproductive senescence in aged red deer hinds - Fisher MW; McLeod BJ; Mockett BG; Moore GH; Drew KR (Proceedings of the New Zealand Society of Animal Production, 1996)
This study reports on the performance of some of the original animals used to establish the Invermay deer farm. These comprised a selection of some of the original 1973 animals, 21 hinds of unknown age and 19 of the first hind calves born at Invermay in that year. Reproductive performance, expressed as the percentage of hinds weaning calves, decreased slowly from 90% at 6 and 7 years of age, to 50% at 17 years, then dropped markedly with only one calf being successfully reared in each season when the hinds were 19 and 20 years. Similarly, few (5/21) of the older unknown-age hinds raised calves when > 17 years old. When blood sampled twice-weekly during the breeding season (rising 21 years of age), only 6/12 of the known-age hinds had significant plasma progesterone concentrations, with only 3 animals displaying anything like normal cyclical patterns. In addition, most had elevated plasma LH concentrations. Post mortem examination revealed that all these hinds had small reproductive tracts and very few ovarian follicles at this age. Despite an ability to live beyond 20 years, these results suggest that waning reproductive performance with age may be due to ovarian failure.

The role of the vagal innervation of the gut in insulin release in lactating ewes - Herath CB; Reynolds GW; MacKenzie DDS; Davis SR; Harris PM (Proceedings of the New Zealand Society of Animal Production, 1996)
The vagal innervation of the pancreas and upper gastrointestinal tract has been implicated in the release of insulin in response to hyperglycaemia in several mammalian species. Therefore the role of the vagal innervation of the abomasum and upper small intestine in the release of insulin and its effect on glucose metabolism was studied in lactating ewes because of the importance of glucose for milk synthesis and secretion in ruminants. Vagal fibres innervating the abomasum, pylorus and duodenum were sectioned in 3 lactating ewes (VAG); 3 control lactating ewes underwent sham- operations (SHAM). Seven and 14 days after the surgery, all animals were given an intravenous injection of glucose (100 mg/kg BW) and jugular blood samples collected for glucose and insulin determinations. Plasma glucose concentration (mean

Seasonal changes in FSH and LH concentrations in ewes with gonadal hypoplasia: Evidence that steroid-independent mechanisms control seasonality in sheep? - McLeod BJ; Kyle SE; Ramsay MR (Proceedings of the New Zealand Society of Animal Production, 1996)
Current hypotheses for the control of seasonality are based on the premise that seasonal changes in sensitivity to ovarian steroid hormones drive changes in reproductive status. Most studies have used the ovariectomised, oestrogen-treated ewe as an experimental model, but such animals may be influenced by previous entrainment or exposure to gonadal steroids. This study uses an infertile animal - the homozygous Inverdale ewe - as a unique

Seasonal effects on fetal growth in sheep - McCoard SA; Peterson SW; Jenkinson CMC; Campbell JW; McCutcheon SN (Proceedings of the New Zealand Society of Animal Production, 1996)
Previous studies have shown that autumn-born lambs are lighter (by 0.4 to 1.0 kg) at birth than spring-born lambs, an effect which is associated with impaired placental development in ewes mated to lamb in the autumn. As previous studies have focused on near-term fetal weights and birth weights, the objective of this study was to determine the pattern of growth throughout gestation in lambs destined to be born in the autumn or spring, and to examine associated changes in placental development. Mature N.Z. Romney ewes were randomly assigned to groups mated in December (n=23) or March (n=28) and managed on pasture in both seasons for similar live- weight profiles from mating to day 140 of gestation. Ewes were slaughtered at day 56, 84, 112 or 140 of gestation, and measures of fetal and placental weight were determined. Fetal weights (kg) of December- versus March- mated ewes were: d56 (0.040

Sequence variations in genes coding for bovine Beta-lactoglobulin and alpha S1-casein - Wilkins RJ; Davey HW (Proceedings of the New Zealand Society of Animal Production, 1996)
The techniques involved in searching for bovine milk protein variants by the direct sequencing of genes are discussed. Examples are drawn from our studies of two major milk protein genes, b-lactoglobulin and aS1-casein. In the former case it was possible to subdivide the A and B variants even further according to point mutations found in the promoter region of the gene, while in the latter case, a New Zealand aS1 casein type A variant in Friesians was shown to arise from a point deletion in the gene which differs significantly from a mutation reported to give rise to the same type A variants in the German Red breed. The potential of this analytical approach for analysing milk protein genes is discussed.

Sperm numbers, semen age and fertility in fresh and frozen bovine semen - Vishwanath R; Pitt CJ; Shannon P (Proceedings of the New Zealand Society of Animal Production, 1996)
The consequence of a seasonal mating pattern is that a significant amount of semen from the top sires is required during this intensive mating period to satisfy the demand. To utilise semen from these top sires efficiently, liquid semen technology has been extensively used in New Zealand. This paper describes the essential physiological differences between liquid and frozen semen and their relative advantages and disadvantages. Alternative technologies such as freezing semen in bulk and later rediluted for use as liquid semen can be used to overcome the constraints of an intensive mating season.

Structural characteristics of the sheepbreeding industry and implications for genetic and reproductive technologies - Stewart JB; Garrick DJ (Proceedings of the New Zealand Society of Animal Production, 1996)
The structure of the sheep breeding industry needs to be understood and documented in order to assess the possible gains resulting from the implementation of genetic and reproductive technologies. This paper reports a structural description of the sheep industry, which apart from census information obtained every 5 years has received little attention since 1948. The proportion of the national flock represented by the minor and

Supplementary feeding and gastrointestinal nematode parasitism in young grazing sheep - Van Houtert MFJ; Barger IA; Steel JW (Proceedings of the New Zealand Society of Animal Production, 1996)
Young Merino wethers (n=240) were allocated to 1 of 8 treatments in a replicated field experiment. Animals grazed semi-improved pasture and received supplements for 14 or 28 weeks based on fish meal (F14, F28), sunflower meal (S14, S28) or oat grain (O14, O28). Unsupplemented parasite-free (C-) and parasitised animals (C+) were included as controls. Animal performance and parasite status were evaluated. During weeks 1-14 faecal egg counts (FEC) were below 120 eggs per gram (epg), due to low larval intake from pasture. Cumulative live-weight gain (LWG) over this period was increased as a result of supplementary feeding from 8.6 (mean C- and C+) to 11.4 kg (F14; P<0.01) or 9.9 or 9.7 kg (S14 and O14 respectively; P>0.05). From week 15 animals were dosed fortnightly with 6000 Trichostrongylus colubriformis and 2000 Haemonchus contortus larvae. Lucerne hay was fed twice weekly from week 17 onwards (2 kg/sheep/week). The FEC increased to about 5900 epg in week 28 for groups C+, F14, S14, O14 and O28 and about 3000 epg for groups F28 and S28 (P<0.05). Cumulative LWG from weeks 15-28 for groups C-, F28, S28 and O28 (0.9, 1.1, 0.6 and 1.4 kg respectively) was higher than for groups C+, F14, S14 or O14 (-1.2, -1.7, - 2.2 and -0.9 kg respectively; P<0.05). Supplementation with F, S and O during parasite infection enhanced the resilience of grazing sheep to gastrointestinal nematodes, while supplementation with F and S appear to have reduced peak FEC.

The use of a novel approach to determine the influence of sward characteristics on the discriminatory grazing behaviour of dairy cows - Griffiths WM; Hodgson J; Holmes CW; Arnold GC (Proceedings of the New Zealand Society of Animal Production, 1996)
Dairy cows were offered choices of patches of vegetation (0.8m2) on a perennial ryegrass (Lolium perenne L.) sward providing combinations of five levels of sward height (8.9 - 19.6 cm) and three levels of herbage bulk density (1.3 - 1.6 mg DM/cm3) in linear sequence. Four cows were used, each of which grazed two out of a balanced set of eight sequences, each sequence being replicated three times in a set of 27 patches in linear sequence. Animal responses were monitored in terms of grazing time and number of bites per patch. Bite number per patch increased from zero to 54 (SEM

Use of bovine oocytes for the evaluation of ram semen - Smith JF; Murray GR (Proceedings of the New Zealand Society of Animal Production, 1996)
In vitro fertilisation (IVF) is one of a range of procedures used to evaluate the fertility of ram semen. This paper reports on the development of a heterologous IVF test, using bovine oocytes for the evaluation of frozen ram semen. An initial comparison of frozen bull (B) and ram (R) sperm with bovine oocytes using either TALP or SOF media showed a significant (P<0.001) species by media interaction on the percentage of fertilised oocytes (B-TALP 88.2

Utilisation of methionine by the mammary gland of the lactating goat - Lee J; Treloar BP; Sinclair BR; Prosser CG; Davis SR; Harris PM (Proceedings of the New Zealand Society of Animal Production, 1996)
The goat milk protein, a-lactalbumin, contains no methionine residues, hence if 35S label is supplied to the gland in the form of labelled methionine only, the appearance of 35S in a-lactalbumin gives a measure of transsulphuration of methionine to cysteine within the gland. Two lactating Saanen goats were surgically modified with catheters implanted in the mammary milk vein, femoral and external pudic mammary artery, and jugular vein to enable infusion of 35S-methionine, into either the whole body (jugular) or directly into the gland, and repetitive blood sampling. Specific radioactivity of methionine in the blood and milk proteins was determined at hourly intervals for 9 hours. Radioactivity of 35S was determined in a-lactalbumin when 35S-methionine was supplied directly to the gland via the mammary artery, but could not be detected when supplied via the jugular vein. Analysis of mammary tissue from the latter experiment did however show the appearance of 35S label in the intracellular cysteine pool which was derived from methionine. Both approaches suggested that transsulphuration within the gland, although small, may be important especially when supply of methionine to the gland is high. The fractional extraction of plasma methionine by the gland for two goats was 46.4

Variation in fleece characteristics over the body of alpacas - Newman S-AN; Paterson DJ (Proceedings of the New Zealand Society of Animal Production, 1996)
Variation in fleece characteristics over the body of alpacas was examined in order to determine the optimum sampling site to provide an estimate of overall fleece properties. Fibre samples were taken from the neck, shoulder, midside, mid-back and rump positions on 35 mature female alpacas. Yield was significantly (P<0.0001) lower on the neck and back and higher on the rump than on the shoulder and midside sites, 91.1, 91.0, 94.4, 94.0, 93.2 % (se 0.3) respectively. Staple length varied significantly (P<0.001) between all sites. Fibres on the neck were considerably shorter than at other sites, with staple length at the neck only 56.7 mm compared to the other sites where length was between 80 and 100 mm. Staple length increased from rump (81.9 mm) to shoulder (99.6 mm) and from the back (86.4 mm) down the midside (92.8). Fibre diameter did not vary over the fleece (mean 33.3

Variation in meat pH in steers and association with other carcass attributes: analysis of a commercial database - Smith DR; Wright DR; Muir PD (Proceedings of the New Zealand Society of Animal Production, 1996)
Measurements of meat pH on 16905 steer carcasses supplied to the Richmond Asian Beef Programme in the 1993/94 and 1994/95 seasons were analysed for variability between suppliers and associations between pH and other carcass attributes. Carcass measurements were made 12 hours or later after slaughter. Factors evaluated included carcass weight, carcass grade, marbling level, age of cattle, mob size, and use of growth promotants. The frequency distribution of meat pH was highly skewed, with 92% of carcasses falling within the range of 5.2 to 5.8, and the remainder forming a long tail above 5.8, ranging to an extreme value of 7.1. For carcasses falling in the pH range of 5.2 to 5.8, pH showed a highly significant positive association with meat colour. As pH rose above 5.8, the slope of the relationship increased and the percentage of carcasses in the darkest meat colour category rapidly approached 100%. In the range 5.2 to 5.8, pH showed highly significant negative (P< 0.0001) associations with degree of marbling and carcass weight. After adjusting for carcass weight and marbling score, pH showed a significant positive association with age of cattle. The percentage of carcasses with a pH above 5.6 was 38% for carcasses with a marbling score of 1. For every unit increase in marbling score (up to 5), the percentage of carcasses above a pH 5.6 specification declined by approximately 5%. However, the proportion of carcasses with pH above 5.8 showed little association with marbling. Similarly, effects of weight and cattle age on pH were much more apparent near the mean pH (5.61) than at pH values at and above 5.8. Mob size had a small but highly significant(P<0.001) effect on the frequency distribution of pH, with smaller mobs tending to have lower pH. The effect of smaller mob size was more evident near the high pH range than in the middle of the frequency distribution. For mobs of 15 or fewer cattle, 94% of carcasses had a pH of 5.8 or less. For mobs larger than 15, 91% of carcasses met this specification.

Variation in sheepmeat odour and flavour - Young OA; Braggins TJ (Proceedings of the New Zealand Society of Animal Production, 1996)
Sheepmeat odour and flavour has received only spo-radic interest from flavour researchers probably because the species has only minor importance in the huge beef and pork dominated markets of North America and Japan. The characteristic odour and flavour of sheepmeat is one of the reasons its consumption is very low in these affluent markets (Young et al.,1994).

Varying the form of oestradiol administration in anoestrous cows previously treated with progesterone - Macmillan KL; Taufa VK; Day AM (Proceedings of the New Zealand Society of Animal Production, 1996)
The hypothesis tested in this field trial was that 1 mg oestradiol benzoate (ODB) could be equally effective where administered to anoestrous animals either by intramuscular injection or in a gelatin capsule per vaginum. The ODB treatment was administered to 412 cows in 8 dairy herds 24 h after the end of a 6-day priming treatment with progesterone, also administered per vaginum. By 48 h after ODB administration, 87% of injected animals had been detected in oestrus and inseminated compared to only 44% of herdmates receiving the gelatin capsule (P<0.01). Re-examination of those animals not detected in oestrus by 13 days after ODB treatment showed that 30% of capsule-treated animals were still anoestrus and another 10% had ovulated without being detected in oestrus. Comparable percentages for the injected animals were 3% and 2% respectively (P<0.01). The vaginal treatment was also associated with a reduced pregnancy rate to first insemination (31.7% vs 47.7%; P<0.05). The reduced efficacy associated with the vaginal administration of ODB to anoestrous animals most probably involved a prolonged rate of absorption which did not stimulate behavioural oestrus or an ovulatory surge of LH but did reduce fertility in those animals which were inseminated.

A view of the markets for beef and lamb and potential opportunities - Burtt A; Francis L (Proceedings of the New Zealand Society of Animal Production, 1996)
This paper identifies some of the changes that have occurred in New Zealand

We couldn't do it without 'em! - Shackell GH (Proceedings of the New Zealand Society of Animal Production, 1996)
The job I found most difficult during my tenure as President of this Sociery,was writing tomembers whose abstracts had not been accepted for the conference. The irony is, that a term as President carries with it the implicit responsibility of presenting a paper that does nut go through a selection process. Even more ironical is that in 1976, the incumbent President Alan Kirton noted in his annual report to the AGM, the consensus of the management committee was that in future the Presidential address should be an optional rather than an obligatory feature of the conference.

A whole farm approach to feed planning and ration balancing using UDDER and CAMDAIRY - Uribe JV; Parker WJ; Dake CKG; McDonald A (Proceedings of the New Zealand Society of Animal Production, 1996)
The potential of New Zealand cows for milk production remains substantially under-utilised as a consequence of pasture-based feeding systems. One means to increase per cow production is to balance pasture diets to provide the correct quantities and ratios of nutrients to meet target levels of milksolids production, but this needs to be done in a manner which is profitable and consistent with good pasture management. The dairy farm simulation model, UDDER, was used to evaluate supplementation strategies for early and late lactation in order to increase milk yields per cow and the farm gross margin. A sample of diets from UDDER were then tested with a ration balancing model (CAMDAIRY) to identify nutrient limitations to milk production. Undegraded protein (UDP) was limiting in all diets. It was concluded that, ration balancing would be useful aid to feed management on New Zealand dairy farms, but in practice could only be sensibly used if feed and animal monitoring systems are in place to determine the type(s) and period(s) of supple

Winter feeding of twinning beef cows - Lambert MG; Devantier BP; Betteridge K; McMillan WH; Pugh PA (Proceedings of the New Zealand Society of Animal Production, 1996)
A grazing trial was conducted in southern North Island hill country during 1994, to determine the influence of pasture allowance during winter on cow/calf performance of 40 twin- (T) and 40 single-calf (S) bearing Friesian-cross beef cows. Groups of T and S cows were grazed at low (L), medium (M) and high (H) pasture allowances for the last 4 months of gestation. Average LW in late autumn was 467 kg, and change up to 4 weeks pre- calving was LS -7.8%, MS -2.4%, HS +1.5%, LT -8.1%, MT -3.0%, HT - 3.5%, suggesting S cows responded to a increased pasture allowance in late gestation, but T only to M and no further to H. Blood serum bOH concentration, which was used as a measure of energy status, was not influenced by allowance treatment, but T (2.2 mmol/l) had higher concentrations than S (0.9). Twinning cows had a shorter gestation length than S cows (277 vs 284 d). Twin calves were lighter at birth (30.9 vs 44.2 kg), had lower perinatal survival (73 vs 96%), and grew more slowly to 4 months of age than single calves (0.76 vs 1.11 kg/d). Our results suggest that

Adapting cattle from pasture to brassica diets - Woods PW; Couchman JN; Barlow HA (Proceedings of the New Zealand Society of Animal Production, 1995)
Strategies for adapting cattle from pasture to brassica diets were compared. Groups of 20 Friesian weaner bulls were offered three diets at a fixed daily allowance of 12% of liveweight as drymatter on offer, for a six week period during February and March 1994. Animals continuously grazing pasture and a Wairoa brassica crop were compared to a group receiving half their allowance as pasture and half as Wairoa brassica, in separate night and day breaks. Unfasted animal liveweights were measured each week for the duration of the trial. Utilisation and botanical compositions were estimated from quadrat harvests to ground level before and after grazing. Liveweight differences among treatments at the start (overall mean 178.9 kg) and at the finish of the trial (overall mean 207.4kg) were non statistically significant (P>0.09), although growth paths differed between treatments. Both groups receiving brassica initially lost weight, the effect being most pronounced after the first week when growth rates were -0.28 kgLW/day in brassica, 0.36 kgLW/day in pasture, and -0.77 kgLW/day in the mixed diet (P<0.05). During the final week of the trial growth rates were 1.12 kgLW/day, 1.86 kgLW/day and 1.44 kgLW/day for brassica, pasture and mixed diets respectively (P<0.05). Overall average growth rates did not differ significantly (P>0.10). Large areas of crop will be required to fully realise the benefits of short term rapid growth rates.

Alkane technology estimates of summer and winter herbage intake of four specialty carpet wool breeds, Romneys and Merinos - Champion SC; Robards GE; Lindsay AR; Friend MA (Proceedings of the New Zealand Society of Animal Production, 1995)
Groups of between 12 and 39 mixed age alpaca females with young at foot, and similar numbers of non-lactating Wiltshire Horn sheep, were grazed in three sets of paired plots of mixed perennial ryegrass/white clover/Yorkshire fog/cocksfoot pastures. Each pair of plots was grazed twice over a period of four months (January-June) in order to compare patterns of grazing behaviour and diet selection. All pastures contained substantial proportions of dead material. Grazing behaviour was recorded manually over 24 hours in each period, and diet selection assessed from marked grass tillers and clover nodes set out on long transects in each plot. Alpacas and sheep spent similar time grazing (8.7 vs 8.5

Antibody class-specific immune responses in ovine milk measured by ELISA - Hodgkinson AJ; McQuoid MR; Hodgkinson SC (Proceedings of the New Zealand Society of Animal Production, 1995)

Apple pomace as a supplement to pasture for dairy cows in late lactation - Edwards NJ; Parker WJ (Proceedings of the New Zealand Society of Animal Production, 1995)
Eye muscle dimensions of meat and fat together with live or carcass weight are important selection criteria for the improvement of carcass traits in sheep. The use of B-mode ultrasound may offer scope for more efficient progeny testing procedures. Two trials examined the use of ultrasound for estimating eye muscle width (A) and depth (B) between the twelfth and thirteenth ribs on live animals, and their carcasses immediately following slaughter and up to nine hours later. These estimates were then compared with ruler measurements on the eye muscle cut surfaces. Correlations between the various estimates of B were high (r = 0.80 to 0.96). While the correlation between the live scan of A and its ruler measurement was 0.75, the correlations between carcass scans and ruler measurements were 0.40 to 0.61. This was due to difficulty in maintaining acoustic coupling over the length of the probe, which was flat relative to the curved carcass surface. A new curved offset offers excellent prospects for overcoming this problem.

Assessment of lamb meat quality in Sydney and Melbourne - Hopkins DL; Ferrier GR; Channon HA; MacDonald BA (Proceedings of the New Zealand Society of Animal Production, 1995)
Over two years at Whatawhata Research Centre mixed age Hereford x Friesian beef cows pregnant with either one or two calves were compared in a feed intake study. Pasture dry matter (DM) intake by the cows was estimated using slow- release, chromic oxide, rumen capsultes. Twin pregnant/suckled cows ate similar amounts per day as

The behaviour of calves tail docked with a rubber ring used with or without local anaesthesia - Petrie NJ; Stafford KJ; Mellor DJ; Bruce RA; Ward RN (Proceedings of the New Zealand Society of Animal Production, 1995)
The concentrations of cholesterol and triglyceride in blood plasma were compared in two genetically distinct herds of Angus cattle. Any concentration differences between the herds should indicate a realised genetic response to selection for yearling weight. Seventy-four yearling Angus cattle from the Waikite weight selection and control herds were blood sampled after a 24-h fast in July, September and November 1993 (heifers twice, bulls three times; n=178 samples). Plasma cholesterol concentrations averaged 2.73 and 2.91 (s.e.d. 0.08) mmol/l in the two herds, respectively (P<0.05), and triglyceride concentrations averaged 0.296 and 0.316 (s.e.d. 0.015) mmol/l, respectively. There was a 30kg (14%) difference in yearling live weight between the two herds (P.001). Both metabolites showed moderate between-animal repeatabilities, 0.52+0.11 and 0.37+0.16 respectively, and there was a positive phenotypic correlation of 0.40 between cholesterol and triglyceride concentrations within herds. These results show that a 14% higher weight-for-age as a result of selection was associated with a 6% lower plasma cholesterol concentration. This was consistent with our previously observed cholesterol difference in cooked beef from the same herds.

Bio-impedance monitoring of genital tissues of cows as an aid in cattle reproductive management - a review - Lehrer AR; Lewis GS; McMillan WH; Aizinbud E (Proceedings of the New Zealand Society of Animal Production, 1995)

Brief Communication - The cost of producing feedlot beef in New Zealand - Muir PD; Smith NB; Wallace GJ (Proceedings of the New Zealand Society of Animal Production, 1995)
In recent years there has been considerable interest in feedlotting as a means of producing beef carcasses with more desirable characteristics (eg. improved fat colour, marbling). This paper outlines the cost of feeding heavyweight cattle on a feedlot ration and the likely premiums required to meet this additional cost. In three experiments Angus steer were fed 70% grain diets ad libitum for at least 14 weeks. In experiments 1, 2 and 3, respectively, steers grew from 621 to 761 kg, 574 to 674 kg and 563 to 657 kg, over 70, 68 and 71 day period, respectively. Feed intakes averaged 15.2 kg of dry matter per day and were 2.2% of bodyweight. Average liveweight gain was 1.60 kg/day and average feed conversion efficiency was 9.5 kg feed per 1 kg of liveweight gain. Based on typical New Zealand feed costs, the average daily feed cost was $3.44 per head and the premium required to recoup the feed cost alone would need to be $1.18 per kg of total carcass weight. Approximately $1.48 per kg would be required to cover all costs.

The Calpain System - genotype, nutrition and their interactions - Speck PA; Singh KK; Thomson BC; Dobbie PM; Mercer GK; Bass JJ; Simmons N; Binnie B; Clarke N (Proceedings of the New Zealand Society of Animal Production, 1995)
Three groups of pregnant (3rd trimester) cows grazing low Se pastures were given daily Se intakes of 0.44, 0.94 and 1.44mg respectively as pasture plus a drench. A significant relationship between blood Se concentration (nmol/l) [y] and daily Se intakes (mg/day) [x] was described by the equation Y=147(44.0+(359(42.1)X***. Given that a mean blood Se concentration of 250 nmol/l reflects an adequate Se status, that is there is no production response to Se supplementation, then the daily Se intake of pregnant cows was determined to be 0.29mg or pasture should contain 0.037mg Se/kg DM to prevent Se deficiency.

Calving patterns in dairy heifers following single 'set-time' inseminations and re-synchrony preceding second inseminations - Cliff SC; Morris GR; Hook IS; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 1995)
Retail audit studies were undertaken in both Sydney and Melbourne to establish benchmarks for quality at the retail level. Midloins were obtained from ticketed carcasses at 14 retail outlets in Sydney, on 3 occasions (2x3) during the same week in March 1994. In Melbourne, midloin samples were obtained from non-ticketed carcasses in 38 and 40 retail outlets in June 1993 and January 1994 respectively. Using an L* value of 32 and a pH value of 5.8 as criteria of acceptability it was found that similar numbers of unacceptable samples occurred in both cities. Using a Warner Bratzler (WB) shear force of 5 kg as an indicator of unacceptable toughness, 15% of samples from Sydney were unacceptable compared to 5% in Melbourne. Carcass age significantly (P<0.001) influenced the WB values for Sydney samples. When WB values were adjusted to 1 or 3 day old equivalents 27% and 6% exceeded 5kg respectively. The results indicate that management options (such as aging), and objective measurement of carcass and meat quality can be applied to increase knowledge and improve the overall quality of lamb and its reputation with consumers.

Characteristics of seasonal dairy farms achieving high per cow production in the lower North Island of New Zealand - Crawford HK; Gray DI; Parker WJ; Edwards N (Proceedings of the New Zealand Society of Animal Production, 1995)
The accuracy of multi-frequency bioimpedance analysis (MFBIA) as a predictor of carcass composition in lambs was assessed in a small study. Impedance and its

Commercial performance of sheep carrying the Inverdale gene (FecX) - Gray AJ; Davis GH (Proceedings of the New Zealand Society of Animal Production, 1995)
The progeny testing of 12 Romney rams from a family in the Woodlands high prolificacy flock provided an opportunity to improve the 88% lambing percentage from the 3200 ewe flock on a Southland farm. Over four years, ewes with the Inverdale gene averaged an extra 35 lambs weaned per 100 ewes jointed. The little size averaged 2.38 for Inverdale ewes, with 11% having singles, 45% twins, 39% triplets and 5% quadruplets. More than 80% of Inverdale ewes reared>lamb, and the second generation Inverdale ewes reared larger and more lively lambs. Weaning weights at 12 weeks of age averaged 22kg, which, due to the large number of lambs reared as multiples, was lighter than the commercial flock. However, by eight months of age Inverdale and commercial hogget weights were similar. High feeding levels during lactation have been critical to the success of the Inverdale flock.

Comparison of cervical, transcervical and laparoscopic insemination of ewes with chilled stored and frozen ram semen - Smith JF; Parr J; Beaumont S; Oliver JE; Upreti GC (Proceedings of the New Zealand Society of Animal Production, 1995)
A technique for transcervical artificial insemination (TAI) of the ewe has been reported as an alternative to laparoscopic intrauterine insemination (LAI). This study evaluated the techniques under New Zealand conditions. Romney ewes (365) were treated in February for 14 days with CIDR

A comparison of protocols for the photoperiodic induction of synchronised wool follicle growth cycles - Craven AJ; Parry AL; Ashby MG; Pearson AJ (Proceedings of the New Zealand Society of Animal Production, 1995)
This study endeavoured to characterise the effects of breed and calving liveweight (CW) on postpartum (pp) ovarian activity in 16 Friesian (F) and 16 Jersey (J) heifers. Half of the animals within each breed were differentially fed (High vs Low: H vs L) during the 8 weeks before calving to achieve CWs (24 h pp) of 404 (FH), 354 (FL), 334 (JH) and 279 (JL) kg. They were fully fed as one group after calving. Ovarian ultrasonography showed that the FL group had the longest postpartum anovulatory interval (PPAI) of 77 days compared to 47 days among other groups. The second dominant follicle pp emerged 6 days later in FL heifers. Breed, but not CW, affected follicle patterns in the first normal oestrous cycle. Underfeeding of Friesian heifers during late pregnancy extended the PPAI whereas Jerseys were not affected to the same extent.

Compensatory growth in cattle - revisited - Nicol AM; Kitessa SM (Proceedings of the New Zealand Society of Animal Production, 1995)
Perendale flocks bred for divergence in lambs

Contract Summary - Rohloff M (Proceedings of the New Zealand Society of Animal Production, 1995)

Cortisol response to ACTH in lambs selected for or against fatness: Effects of maturity and fasting - Veenvliet BA; Littlejohn RP; Stuart SK; Suttie JM (Proceedings of the New Zealand Society of Animal Production, 1995)
Lambs grazing the tannin containing pasture species Lotus corniculatus (cv Goldie) were compared with lambs grazing a high endophyte ryegrass (cv Nui) in order to assess the effectiveness of lotus at reducing dags and flystrike. Two trials of the same design were run consecutively, between January and April 1994. Each of 4 paddocks, 2 of lotus and 2 of ryegrass, were set stocked for 32 and 42 days (respectively for trials 1 and 2) with 62 lambs. Half of the lambs in each paddock were drenched fortnightly with a combination anthelmintic. Lambs were examined for flystrike three times each week and samples were collected for fly identification before strikes were treated with insecticide. Lambs which grazed lotus suffered less flystrike than those grazed on ryegrass in both trials (32% of 51%; P<0.01 and 1.5% cf 7.4%; P<0.05 for trials 1 and 2 respectively). Drenching reduced flystrike in trial 1 (from 57% to 26%; P<0.01), but not in trial 2 (4.8% cf 4.1%; NS). Flystrike was strongly correlated with dagginess (R2=97%). Mean dry weight of dags was reduced by grazing lotus rather than ryegrass (79g cf 108g; P<0.01 in trial 1 and 9.7g cf 14.3g; NS in trial 2) and by drenching (68g cf 118g; P<0.01 in trial 1 and 8.8g cf 15.2g; NS in trial 2). Lambs grazing lotus had significantly (P<0.01) higher faecal dry matter content than those grazing ryegrass. We conclude that lotus has considerable potential for a future role in the integrated management of flystrike and dags.

Dagginess and flystrike in lambs grazed on Lotus corniculatus or ryegrass - Leathwick DM; Atkinson DS (Proceedings of the New Zealand Society of Animal Production, 1995)

Development of a management system to intensify and increase beef production in a range suckler herd in Israel - 'the Amaziah project' - Lehrer AR; Kahn HE; Kreitzer J; Gacitua H; Mizrachi Y; Kali J (Proceedings of the New Zealand Society of Animal Production, 1995)
Repeated sheep treatment with the anthelmintic drug benzimidazole (BZ) resulted in selection of genetically benzimidazole-resistant (BZ-R) nematodes, which code for a specific allele of isotype 1Beta-tubulin. The presence of this allele was tested in the Waikato ovine nematode, using an allele specific PCR. Two isotype allele specific oligomers for O. circumcincta (O.c.) Beta-tubulin gene were designed. The last base at the 3

Differences in propensity of wool to develop yellow discolouration in flocks of Perendale sheep selected for and against - Reid TC; Botica KJ; Sumner RMW (Proceedings of the New Zealand Society of Animal Production, 1995)
CONFIRM is a recently developed test kit for verifying pregnancy in dairy cows on the basis of the concentration of oestrone sulphate (OS) measured in a milk sample taken at least 120 days after mating/insemination. In this study, the performance of CONFIRM was evaluated using milk samples from non-pregnant cows returning a

Discovery of the Inverdale gene (FecX) - Davis GH; McEwan JC; Fennessy PF; Dodds KG (Proceedings of the New Zealand Society of Animal Production, 1995)
Selection for ovulation rate in a screened prolific flock identified a prolific family of Romneys in 1984 that descended from one ewe, and progeny tests for her male descendants carried out from 1985 to 1990 indicated the presence of a major gene (Inverdale) on the X- chromosome. One copy of the gene increases ovulation rate by about 1.0 and litter size by about 0.6. However, research in 1991 found that ewes with two copies of the gene have small non-functional 'streak' ovaries and are infertile. Many of these infertile ewes develop tumour-like structures on their ovaries and these are currently the subject of intensive research. In 1993 a prolific Romney flock in Tokoroa, with no known connection with A281, was also found to have the Inverdale gene. The place of the Inverdale gene in industry will be to increase prolificacy in ewe flocks mated to terminal sires, and a research programme has been established to identify a genetic market for ram breeders.

Early lactation response of dairy cows to pasture under two different nitrogen fertiliser regimes - Mackle TR; Parr CR; Bryant AM (Proceedings of the New Zealand Society of Animal Production, 1995)
Near-infrared (1100-2500 nm) reflectance spectra were measured on 128 beef ribeye samples using a scanning monochromometer and calibrated against standard laboratory analysis to develop a rapid method for measuring intramuscular fat of beef. A pilot run was conducted on 38 frozen ribeye samples, ranging in fat content from 94 to 325g/kg dry weight, to evaluate sample preparation methods (frozen slices, thawed slices, coarse mince. After scanning of subsamples, fat content of the sample was then measured using Soxhlet extraction. Standard error of calibration (SEC) was 9g/kg dry weight for spectra collected from minced samples compared to 25g/kg for frozen slices and 15g/kg for thawed slices. A second set of 90 frozen ribeye samples (fat content range 56-305 g/kg dry weight) was used to test and improve this calibration, using 3 subsamples of minced beef per sample. The ability of the initial calibration equation to predict fat content of these samples was poor. A more robust calibration was then attempted by pooling the data from the two sets. The SEC of this extended set was 16 g/kg dry weight (10% of the sample set mean) and the multiple R2 of calibration was 0.92. The standard error of prediction for new samples was estimated from internal cross-validation runs as 19 g/kg. Prediction of fat content of an independent validation set of 24 samples had a standard error of 20 g/kg dry weight. Analysis of the calibration results suggested that a major source of error in the calibration was hererogeneity between subsamples, with the standard deviation of prediction of different subsamples from the same ribeye being larger than the standard error of cross validation. These results indicate that Near-Infrared reflectance spectroscopy may provide a rapid objective method for estimating intramuscular fat of beef.

Effect of allowance and the rate of adaptation of weaned calves to two brassica types - Muir PD; Wallace GJ; Slay MWA (Proceedings of the New Zealand Society of Animal Production, 1995)
Groups of 10 Friesian bull calves averaging 142 kg were offered Winfred forage brassica (62% leaf) at allowances of 3, 6, 9, 12 or 15% of bodyweight (BW) for 6 weeks. Similarly, groups of 8 Friesian bull calves averaging 150 kg were offered Wairoa forage brassica (67% leaf) at allowances of 3, 5, 7, 9 and 12 % of bodyweight. Calves were weighted weekly and offered fresh allowances each week. The two experiments were conducted between January and March of the same year but were not run concurrently. There was a significant effect (P<0.01) of allowance on liveweight gain for calves offered Winfred, with calves on the lowest allowance (3% of BW) growing at 0.90 kg/day, compared to 1.20 kg/day for calves grazing the other four allowances. Calves grazing the low allowance (3% of BW) utilised 77% of the total crop, but only 43% of the stem. On the other hand, calves grazing the low allowance of Wairoa utilised 90% of the total crop and 72% of the stem without suffering a liveweight penalty. There was no effect of allowance of Wairoa on calf growth rate and overall, calves on Wairoa grew at an average of 1.03 kg/day. Choice of a leafy type of brassica maybe important if the objective is a high degree of utilisation coupled with good animal performance. Alternatively, on

The effect of anthelmintic treatment of ewes during pregnancy - Familton AS; McAnulty RW; Thompson KF; Sedcole JR (Proceedings of the New Zealand Society of Animal Production, 1995)

Effect of continuous stocking of breeding ewes at different sward surface heights during the late summer-autumn on herbage intake and productivity - Panggabean AU; Morris ST; Parker WJ; McCutcheon SN (Proceedings of the New Zealand Society of Animal Production, 1995)
This study aimed to raise GnRH antibodies in young bulls (immunocastration) and determine the subsequent effect on behaviour, sexual development, carcass characteristics and meat quality. Thirty Friesian bull calves were assigned to one of three groups balanced by liveweight (control bulls, immunocastrates and steers). At nine months of age (Day 0) immunocastrates were vaccinated against GnRH (Vaxstrate) and boosted one month later (Day 31). Following immunisation there was a rise in GnRH antibody titre and a decrease in testosterone. Control animals gained significantly more weight than immunocastrates and steers in the first 157 days. Overall there was no difference in weight gain between controls and immunocastrates. Mean scrotal diameter of immunocastrates decreased from Day 31 to Day 110 and then rose to reach a diameter similar to those of the control bulls by Day 322. Leg wear scores were lower for treated animals compared to controls until Day 230 of the trial, although these differences were not significant. Immunocastrates had a significantly higher mean ultimate pH than both control bulls and steers. Bulls were significantly leaner than immunocastrates, and both groups were leaner than steers.

Effect of control of internal parasitism on productivity of Merino breeding ewes - Sumner RMW; Watson TG; Hosking BC (Proceedings of the New Zealand Society of Animal Production, 1995)

Effect of diluent type and storage time on the pregnancy rate of ewes inseminated laparoscopically with chilled ram semen - Smith JF; Parr J; Murray G; Oliver JE; Beaumont S; Upreti GC (Proceedings of the New Zealand Society of Animal Production, 1995)
Five trials involving 879 ewes were conducted in November, December 1993, February, March and April 1994. Ewes were synchronised with CIDR