@conference {3672, title = {Calf and heifer development and the onset of puberty in dairy cows with divergent genetic merit for fertility}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {77}, year = {2017}, month = {06/2017}, pages = {205-210}, address = {Rotorua}, abstract = {A research herd with divergent genetic merit for fertility was established to better understand the underlying drivers of fertility in dairy cattle. This paper describes the establishment of this herd, heifer growth and development, and the effect of divergence in fertility breeding value (FBV) on the timing of puberty. The average FBV of the high and low fertility groups of heifers was +5.6 and -4.6, respectively. The heifers were weighed fortnightly, with body condition score (BCS) and stature recorded at six, nine, 12 and 15 months of age. Weight and age at puberty were defined as the first day when plasma progesterone was >1 ng/ml in two of three consecutive once weekly samples. There was no effect of FBV on live weight (LWT), BCS, nor stature by age as the heifers matured. High-fertility heifers attained puberty at a lighter LWT (271 vs. 296 kg; SED 4.3 kg), an earlier age (358 vs. 379 days; SED 6.0 days) and a lower proportion of estimated mature LWT (51 vs. 55\%; SED 0.7\%), compared with Low-fertility heifers. Therefore, the premise that high genetic merit for fertility is positively associated with reaching puberty earlier is supported. Further work is required to support and assess the value of incorporating a puberty trait into the FBV.}, issn = {1176-5283}, author = {Meier S and Fisher B and Eketone K and McNaughton LR and Amer PR and Beatson P and Bryant JR and Dodds KG and Spelman R and Roche JR and Burke CR} } @conference {3672, title = {Contract session: An overview of postpartum hyperketonaemia and its association with cow health and performance in pasture-based dairy systems}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {77}, year = {2017}, month = {06/2017}, pages = {104-106}, address = {Rotorua}, abstract = {Following calving, dairy cows undergo a period of negative energy balance during which they mobilise body tissue (such as fat) to support the demands of lactation. When the negative energy balance is severe, the inability of the liver to process all the mobilised fatty acids can lead to hepatic lipidosis (i.e., fatty liver disease) and incomplete fatty acid oxidation. The latter results in the hepatic production of ketone bodies, predominantly β-hydroxybutyrate (BHB), which are released into the circulation as the product of ketogenesis. The increased concentration of ketones in blood is known as hyperketonaemia...}, issn = {1176-5283}, author = {Phyn CVC and Kuhn-Sherlock B and Turner S-A and Grala TM and Burke CR and Roche JR} } @conference {3672, title = {Oocyte maturation and quality in dairy heifers with diverse genetic merit for fertility}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {77}, year = {2017}, month = {06/2017}, pages = {29-33}, address = {Rotorua}, abstract = {Oestrous behaviour, cumulus cell-oocyte complex (COC) quality, and steroid concentrations were characterised in dairy heifers of high and low values for fertility breeding value (FBV). The hypothesis was that the greater FBV is partly mediated through improved oocyte quality. Ovum pick-up (OPU) was used to collect COCs from the preovulatory follicle of 40 heifers observed in oestrus. Multiplex Taqman qPCR was used to investigate gene expression in cumulus cells (eight genes) and oocytes (three genes) of the recovered healthy COCs (n=9 per group). Plasma and follicular fluid steroid concentrations were measured using high-performance liquid chromatography. Low-FBV heifers were more active in the first eight hours of oestrus (P<0.05), leading to earlier detection and OPU (P<0.05). Consequently, COCs recovered from low-FBV heifers were morphologically less mature (P<0.05) and tended to have lower expression of genes regulating maturation compared with high-FBV heifers. Our findings suggest COC development is retarded in low-FBV heifers relative to the timing of visually observed oestrus, which may result in a poorly developed oocyte at ovulation. }, issn = {1176-5283}, author = {Reed CB and Meier S and Pitman JL and Burke CR} } @conference {3672, title = {Uncovering genetic variation in cow fertility using simulation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {75}, year = {2015}, month = {07/2015}, pages = {42-47}, address = {Dunedin}, abstract = { Dairy cow fertility is currently measured using two traits: the proportion of cows mated within 21 days of the start of mating (PM21) and the proportion of cows that calve within 42 days of the start of calving (CR42). These traits indirectly measure a cow{\textquoteright}s genetic propensity to return to a fertile state after calving. Both PM21 and CR42 have low heritability (0.05 and 0.03, respectively) and fertility is suspected to have much stronger genetic drivers than indicated by these lowly heritable components. The purpose of this study was to explore genetic and environmental factors that contribute to dairy cow fertility using a stochastic simulation model. The model traces the reproductive life of cows from birth until their second calving date using environmental and genetic variables to simulate fertility phenotypes. The model demonstrated that even when significant genetic variation was simulated in underlying fertility traits, this variation appears only weakly as genetic effects using the current fertility traits evaluated for genetic selection purposes. Potential alternative traits (e.g. gestation length, heifer puberty trait, strength of oestrus expression or post-partum anoestrous interval) were shown to have potential to add value when identifying sires whose daughters calve earlier in the season.}, issn = {1176-5283}, author = {Dennis NA and Stachowicz K and Visser B and Hely FS and Amer PR and Meier S and Burke CR} } @conference {89261, title = {Verification of an automated camera-based system of oestrus detection in dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {73}, year = {2013}, month = {Jan}, pages = {26-28}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {

Accurate oestrus detection is critical in New Zealand dairy farming, where many farms operate a seasonal farming model and, therefore, rely on a compact calving spread and a short mating period to farm efficiently. Automated oestrus detection systems are available that automatically identify and draft cows in oestrus. There are two types of automatic systems available commercially in New Zealand; activity-based systems that involve pedometers/accelerometers and systems that detect mounting behaviour using a sensor attached to the animal{\textquoteright}s back.

}, issn = {1176-5283}, author = {Hempstalk K and Burke CR and Kamphuis C} } @conference {78979, title = {Associations of uterine pathology with milk production and effects of treatment with a nonsteroidal anti-inflammatory drug in dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {72}, year = {2012}, month = {Jan}, pages = {23-27}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {

Subclinical endometritis (SCE) is a form of uterine pathology characterised by an increased proportion of polymorphonuclear cells (PMN) in the uterus post-calving. Previous studies demonstrated a negative association between SCE and lower milk production, with indications that systemic inflammation underlies this link. Accordingly, the hypothesis tested was that treatment with a non-steroidal antiinflammatory drug (NSAID) would increase milk yield in cows with >= 14\% PMN at Day 14. In this study, >= 14\% PMN in the cytological sample collected at Day 14 postpartum was defined as SCE. To test this hypothesis, 213 dairy cows were paired by calving date and Day 14 PMN\%, then randomly assigned to three doses of a NSAID (Carprofen 1.4 mg/kg, n = 103) between 21 and 31 days postpartum or left as untreated controls (n = 108). The effect of the NSAID treatment on milk production was analysed using mixed models. While the results supported previous evidence of a negative association between SCE and milk production, NSAID had no effect on either PMN \% at Day 42 or milk production (P \> 0.1) in this study. The lack of a NSAID effect was possibly because SCE spontaneously resolved in more than 90\% of the cases

}, issn = {1176-5283}, author = {Priest NV and McLeod KLM and McDougall S and Burke CR and Roche JR and Mitchell M and Greenwood SL} } @conference {78982, title = {An evaluation of a progesterone-based diagnostic as an aid to re-insemination decisions in a seasonal, pasture-grazed dairy cow herd}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {72}, year = {2012}, month = {Jan}, pages = {35-37}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {

Progesterone-based diagnostic tests are commercially available to predict pregnancy status 19 to 23 days following an insemination, thus providing decision-making support for artificial breeding. The study objective was to evaluate the likely performance of such a test in a pasture-grazed, seasonal dairy farm. Progesterone was determined in milk samples collected twice weekly from 553 cows at the Lincoln University Dairy Farm. Receiver operating characteristic analysis was applied to these data to determine sensitivity, false positive rate and the positive predictive value using a range of progesterone threshold values for detecting non-pregnant cows. The gold standard was non-pregnancy as measured by ultrasonography. At an optimised threshold of 4.1 ng/mL, the sensitivity, false positive rate and positive prediction rate were 78\%, 2.6\% and 96\% for detecting non-pregnant cows on Days 19 to 23. A major source of inaccuracy was the 28 cows with elevated levels of progesterone in milk on Days 19 to 23 after first insemination that were subsequently diagnosed non-pregnant. Another source of error was the inherent variance in progesterone concentration profiles among individuals. At a current cost of about $5 per test, this technology would have limited appeal for detecting non-pregnant cows in dairy systems where a satisfactory level of oestrus detection performance can be achieved.

}, issn = {1176-5283}, author = {Burke CR and Kamphuis C and Meier S and Pellow R} } @conference {78984, title = {Use of progesterone profiling to investigate factors affecting conception rates in a large, pasture-grazed dairy herd}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {72}, year = {2012}, month = {Jan}, pages = {45-50}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {

A study was conducted at the Lincoln University Dairy Farm to investigate factors influencing conception rate (CR). Relative to the planned start of mating date (Day 0), milk progesterone (MP4) concentrations were determined weekly from Day -20 to 0, twice weekly from Day 0 to 42, and then weekly to Day 70 in 666 cows. Trough-like patterns among individual profiles were identified and defined as periovulatory events. Pre-mating ovulatory status was a predictor (P \< 0.01) of first service CR (FSCR), with anovulatory cows having a lower FSCR (37.4\%) compared with {\textquoteleft}late{\textquoteright} (47.3\%) and {\textquoteleft}early{\textquoteright} (56.4\%) ovulating cows. In turn, interval from calving to Day 0 was a significant determinant for pre-mating ovulatory status. Oestrus detection was performed to a high standard, even though 5\% of the 850 artificial inseminations were coincident with a lack of ovulation. MP4 profiles also indicated that 4\% of cows that conceived during the 37-day artificial breeding period subsequently lost these pregnancies. A 2.6\% error rate for diagnosing pregnancies on Day 78 was detected, mostly due to incorrectly attributing pregnancies following artificial breeding. Findings indicate the critical importance of managerial strategies that promote a high prevalence of cows having ovulated at least 21 days before mating starts.

}, issn = {1176-5283}, author = {Burke CR and Meier S and Pellow R} } @conference {69469, title = {Asssociation among hormones and metabolites during the transition period and early lactation milk production}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {70}, year = {2010}, month = {Jun}, pages = {51-56}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Palmerston North}, abstract = {The transition period is loosely defined as the period from three weeks pre-calving to three weeks post calving, and is regarded as a very important determinant of a cow{\textquoteright}s lactation performance. Data were collated from three experiments in which blood was sampled repeatedly pre- and post-calving and milk production was recorded post-calving. Data were pooled within treatment and associations between blood hormones and metabolites, and milk production determined using regression analysis. Milk and milk solids (MS) yield were positively associated (P <0.05) with pre-calving plasma leptin and glucose concentrations and milk yield was negatively associated (P <0.05) with pre-calving non-esterified fatty acid (NEFA) and β-hydroxy butyrate concentrations. Milk yield was negatively associated (P <0.05) with plasma growth hormone, aspartate aminotransferase, and glutamate dehydrogenase concentrations in the first days of lactation, and with insulin like growth factor and glucose concentrations during the first five weeks post-calving. In comparison, plasma NEFA and albumin (ALB) concentrations post-calving and the ratio of NEFA to ALB were all positively associated (P <0.05) with milk and MS yield during the first five weeks of lactation. Data are consistent with a positive effect of calving body condition on milk production and an increased milk production with increasing condition score loss post-calving.}, issn = {1176-5283}, author = {Edwards P and Mandok K and Lee JM and Burke CR and Kolver ES and Roche JR} } @conference {60934, title = {The effect of feed restriction during peak lactation on milk production parameters : Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {69}, year = {2009}, month = {Jun}, pages = {24-26}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Adverse weather conditions that reduce pasture growth and/or quality can place the lactating dairy cow under periods of transitory nutritional stress. Previous research that has focused on the effects of feed restrictions in a pasture-based dairy system have imposed feed deficits either pre-calving (Roche, 2007), immediately post-calving for five to six weeks (Bryant \& Trigg, 1979; Roche, 2007) or up to a 23\% restriction in dry matter intake (DMI) (Bryant \& Trigg, 1979). All experiments reported an immediate reduction in milk production; however, the longer-term effects varied depending on... Continued }, issn = {1176-5283}, author = {Kay JK and Phyn CVC and Williams YJ and Roche JR and Burke CR and Meier S} } @conference {42024, title = {Presidential Address 2007: The Society{\textquoteright}s role in being empathetic to the animal production industry}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {68}, year = {2008}, month = {Jan}, pages = {1-3}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Brisbane, Australia}, abstract = {Mark Twain once said, "Its better to keep your mouth shut and appear stupid...than to open it and remove all doubt". I considered my strength as President to be more of stewardship than visionary. Alas, it is with some risk to fulfilling Mark Twain{\textquoteright}s prophecy that I continue with this address. I referred to some of the previous Presidential Addresses; to get a feel for what was expected. Certainly, if the Society was to undertake all the {\textquotedblleft}must-do{\textquoteright}s{\textquotedblright} and follow all the visions put forward, we would have made Microsoft Corporation seem like a cake-stall operation by now.}, issn = {1176-5283}, author = {Burke CR} } @conference {41995, title = {Quantifying the importance of submission rate to artificial breeding on reproductive performance and profitability in dairy cattle herds}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {67}, year = {2007}, month = {Jan}, pages = {285-292}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Wanaka}, abstract = {Dexcel{\textquoteright}s Whole Farm Model (WFM) allows the user to construct a mating policy using dates for anoestrous treatment, artificial breeding (AB) and bull mating with corresponding levels of heat detection efficiency. The model then predicts the outcome of the mating programme for each individual animal using an approach based on physiological events, represented by algorithms incorporating current best knowledge. Four commercial dairy farms were initialised in WFM by describing the farm set-up and management decisions for the 2005/06 season. A range of feeding, production and reproduction indicators was used to validate the model predictions against that observed. All four farms had an observed 3-week submission rate (SR) of about 90\%. An alternative scenario with SR at80\% was created for each farm by simulating reduced oestrous detection efficiency during AB. The eight scenarios were then run for 20 random simulations over three consecutive years. The trend was for SR 90\% to result in more milksolids in the second and third years, improved reproductive outcomes and, despite higher AB costs, an increased (P<0.05) economic farm surplus of $80+/ha. This exercise demonstrated that the WFM is capable of simulating reproductive performance in dairy herds and holistically linking this performance to productivity and profit over successive seasons.}, issn = {1176-5283}, author = {Beukes PC and Tiddy RM and Burke CR and Levy G and Lancaster JAS} } @conference {41967, title = {Validation of a technology for objectively measuring behaviour in dairy cows and its application for oestrous detection}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {67}, year = {2007}, month = {Jan}, pages = {136-142}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Wanaka}, abstract = {Devices (IceTag{\textregistered}ActivityMonitor) using accelerometer technology to determine the behaviour of cows (proportion of time lying, standing, active and step count) were attached to 15 cows (2 per cow) and validated between devices and against observed behaviour. For standing and active, 95\% of paired (within cow) one minute data points were within 7\% points, 95\% of the lying data points were within 1\% point, and 95\% of stepping data were within 3 steps. The device recorded 100\% of lying bouts within {\textpm}1 minute of visually observed data. In a second experiment, 16 lactating dairy cows were fitted with IceTag{\textregistered}s and the relationship between behaviour profiles and oestrus evaluated. Blood progesterone concentration and twicedaily visual observations were used to identify precisely ovulation events and four algorithms, based on active and lying behaviour, were developed. A 24 hour rolling mean of activity and a slope threshold of 0.2 calculated for either the previous 10 hours (Activity24/10) or 5 hours (Activity24/5) correctly identified 93\% of oestrous events, with 21\% and 18\% false positive alerts, respectively. Two further algorithms, Lying<20\% or Active>5.5\% between midnight and 05:00hrs identified 50\% and 64\% of oestrous events, with 36\% and 18\% false positive alerts, respectively. In a third experiment using 30 cows, 56 oestrous events were identified through milk progesterone profiles and visual observation. Algorithm Activity24/10 and Activity24/5 identified 84\% and 76\% of oestrous events respectively. The IceTag{\textregistered}accurately recorded several types of cattle behaviour suggesting useful applications as both a research and industry tool.}, issn = {1176-5283}, author = {McGowan JE and Burke CR and Jago JG} } @conference {41652, title = {Effect of genotype and diet on milksolids production, body condition, and reproduction of cows milked continuously for 600 days}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {66}, year = {2006}, month = {Jan}, pages = {245-251}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Napier}, abstract = {Milking cows for two consecutive years, with calving and mating occurring every second year, may exploit the superior lactation persistency of high yielding cows while improving reproductive performance. This study tested the feasibility of extended lactations in pastoral systems using divergent dairy cow genotypes (New Zealand [NZ] or Overseas [OS] Holstein-Friesian [HF]) and levels of nutrition (0, 3, or 6 kg concentrate DM/cow/day). Cows calved on 28 July 2003 and remaining cows were dried off by 6 May 2005. Of the 56 cows enrolled, 93\% were milking at 500 days in milk (DIM) and 18\% were milking at 650 DIM. Dietary treatments did not affect DIM (605 {\textpm} 8.3; Mean {\textpm} SEM), but there was a trend (P=0.09) for OS HF to have longer lactations than NZ HF. Genotype x diet interactions were detected for the total yield of milk and milksolids per cow, and as a percentage of liveweight. Differences between genotypes were greatest at the highest level of supplementation. Compared to NZ HF, OS HF produced 35\% more milk, 24\% more milk fat, 25\% more milk protein, and at drying off had 1.9 units less body condition. Annualised milksolids production from NZ HF was 79\% of a normal season{\textquoteright}s production, compared to OS HF that produced 94\%. Compared to NZ cows, OS cows had a similar 21-day submission rate (85\%), a lower 42-day pregnancy rate (56\% vs. 79\%), and a higher final empty rate (30 vs. 3\%) when mated at 451 days after calving. These results indicate that productive extended lactations up to 650 days are biologically possible on a range of pasture diets, and with appropriate cow genetics and feed management may ameliorate poor reproductive performance in high yielding dairy cows without sacrificing milksolids production. }, issn = {1176-5283}, author = {Kolver ES and Roche JR and Burke CR and Aspin PW} } @conference {41921, title = {A nutrient-signalling effect of grain feeding on postpartum anovulatory intervals in mature dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {66}, year = {2006}, month = {Jan}, pages = {334-338}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Napier}, abstract = {Our previous study with mature dairy cows found that increased pasture intakes in early lactation resulted in more milk being produced but with no change in postpartum anovulatory intervals (PPAI). The present study used a 2 x 2 factorial to determine PPAI in 68 cows with pre- and post-calving diets that were iso-energetic, but varying in the ratio of structural to non-structural carbohydrate. At 36 {\textpm} 8.7 days prepartum, cows were assigned iso-energetic diets (114 MJ ME/cow/day) of either pasture/pasture silage (n=34) or the same diet supplemented with 3 kg DM/cow/d barley-maize concentrate (n=34). After calving, cows within each prepartum diet were assigned iso-energetic diets (179 MJ ME/cow/d) of either pasture/pasture silage (n=34) or the same diet supplemented with 5 kg DM/cow/d concentrate (n=34). Postpartum grain feeding reduced (P < 0.05) PPAI (28.4 {\textpm} 1.8 day) compared to the pasture/pasture silage only diet (36.4 {\textpm} 2.5 day). Prepartum diet did not affect PPAI. Body condition score was inversely related to PPAI at all time points (P < 0.05), but explained little (5-12\%) of the variability in PPAI. Significant relationships to PPAI were also found for blood non-esterified fatty acids, urea and magnesium, but again, r2-values were <= 0.1. None of the milk characteristics measured were significantly related to PPAI. This study supports the premise that discrete or specific nutritional cues unrelated to general energy status can favourably target physiological functions in reproductive tissues at the brain and/or ovarian levels. }, issn = {1176-5283}, author = {Burke CR and Roche JR and Aspin PW and Lee JM} } @conference {41937, title = {Supplementation with concentrates either pre- or post-partum does not affect milk production when diets are iso-energetic}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {66}, year = {2006}, month = {Jan}, pages = {416-422}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Napier}, abstract = {Dairy cow glucose requirements increase dramatically during the weeks preceding calving, suggesting that supplements that increase glucose supply (rapidly fermentable carbohydrates) would reduce precalving mobilisation of body tissue and improve subsequent milk production. Sixty-eight multiparous dairy cows were randomly allocated to one of two diets for 36 {\textpm} 8.7 days precalving. All cows were fed pasture and pasture-silage precalving, with one group also receiving 3kg DM of a barley-maize concentrate. Precalving diets were iso-energetic (114 MJ/cow/day). At calving, cows within each precalving feeding treatments were randomly allocated to two dietary treatments for 35 days in a 2x2 factorial arrangement. Postcalving, all cows received pasture and pasture silage with one group also receiving 5.0 kg DM of a barley-maize concentrate. Postcalving diets were also iso-energetic (179 MJ/cow/day). Milk yield and composition, and liveweight (LW) and body condition score (BCS) were assessed weekly for five weeks. Blood was sampled on day -21, -14, -7, 0, 1, 2, 3, 4, 7, 14, 21, 28 and 35 relative to calving, and plasma samples were analysed for indicators of energy status. Average milksolids yield (1.9 kg/cow/d) during the five weeks postcalving was not affected by either pre- or postcalving concentrate supplementation, although protein to fat ratio was higher in supplemented cows. Similarly, concentrate supplementation pre- or postcalving did not affect either LW or BCS change before or after calving. Cows receiving concentrates precalving had higher (P<0.001) plasma non-esterified fatty acid (NEFA) concentrations, but otherwise were not different to those receiving an equivalent energy intake from pasture and pasture silage. Postcalving concentrate supplementation increased (P<0.01) plasma glucose and NEFA and decreased (P<0.001) plasma B-OH butyrate. Results suggests little effect on milk production by replacing energy from structural carbohydrates in high quality pasture with energy from non-structural carbohydrate during the transition period. }, issn = {1176-5283}, author = {Roche JR and Lee JM and Aspin PW and Sheahan AJ and Burke CR and Kolver ES and Sugar B and Napper AR} } @conference {41571, title = {Effect of pre- and postpartum pasture feeding intakes on postpartum anoestrous intervals in dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {221-224}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Extended postpartum anoestrous intervals (PPAI) are the predominant source of infertility on New Zealand dairy farms. A 2 x 2 factorial design was used to investigate pre- and postpartum pasture feeding levels on PPAI. Sixty-eight multiparous Holstein-Friesian dairy cows due to calve in the first three weeks of the calving period were randomly assigned to a high (11.9 kg DM/cow/day) or low (4.8 kg DM/cow/day) pasture feeding intake for 29 {\textpm} 7.7 days pre partum. After calving, cows within each prepartum feeding level were assigned to a high (13.5 kg DM/cow/day) or low (8.6 kg DM/cow/day) pasture feeding intake for 35 days. At 35 days post partum, cows were grazed as a single group with pasture silage supplementation. Concentrations of progesterone were determined in milk samples collected on Mondays and Thursdays until cows were confirmed to have resumed oestrous cycles or until one week before planned start of mating. High intakes pre-calving increased (P < 0.05) the proportion of cows cycling by the third week postpartum (38 {\textpm} 8\%) compared with a low pre-calving intake (13 {\textpm} 6\%). There was a tendency (P = 0.07) for a reduced mean PPAI in the high (29.7 {\textpm} 2.6 days) versus low (33.4 {\textpm} 2.3 days) pre-calving intake treatments, among cows that initiated oestrous cycles during the experimental period. Post-calving intake did not affect PPAI (P = 0.4), nor was an interaction detected. Body condition score (BCS) at all time points in this study, including before treatments were initiated, was negatively correlated with PPAI (P < 0.05). In contrast, PPAI was not associated (P > 0.1) with changes in BCS during the pre- or post-calving periods, or with milk production characteristics. In this study, resumption of oestrous cycling post partum was strongly linked to pre-existing differences in BCS, and modified by pre-calving pasture intake, but not influenced by feeding intakes or milk production characteristics in early lactation. KEYWORDS: anoestrus; nutrition; dairy cow. }, issn = {1176-5283}, author = {Burke CR and Roche JR and Aspin PW and Lee JM and Taufa VK} } @conference {41570, title = {Effects of feeding level for four weeks precalving on milk production is small and dependent on level of feeding in early lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {215-220}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {The aim was to quantify the relationship between pre- and postcalving level of feeding and their effect on milk production. Sixty-eight multiparous dairy cows were randomly allocated to two levels of pasture feeding (Low and High; 4.8 and 11.9 kg DM/day) for 29 {\textpm} 7.7 days precalving. At calving, cows were randomly allocated (within precalving levels) to two levels of pasture feeding (Low and High; 8.6 and 13.5 kg DM/day) for 35 days postcalving. Daily milk yields were recorded and fat, protein and lactose concentrations determined on 2 days each week for 5 weeks postcalving, and once weekly for an additional 10 weeks post treatment. Body condition score (BCS) at calving was 4.2 and 4.7 for precalving Low and High treatment groups, respectively. Precalving restriction reduced milk fat production by 8.4\% during the first five weeks postcalving, but these differences were not evident subsequently. Postcalving feed restriction reduced yields of milk, fat and protein by 25, 21 and 28\%, respectively, during the first five weeks postcalving. Decreased (P < 0.05) yields of milk, fat and protein (12, 10 and 9\%, respectively) were also evident for ten weeks after the feed restriction finished. There was a trend towards a treatment interaction (P = 0.13) in milksolids (MS) production during the first five weeks of lactation between pre- and postcalving level of feeding. High- High cows produced 7.1 kg more MS than Low-High cows, but there was no effect of precalving level of feeding in cows that were restricted postcalving. Results confirm that level of feeding postcalving influences the milk production effect of precalving feeding. Nevertheless the effect of precalving energy intake on postcalving milk production is small. KEYWORDS: transition cow; pasture; dry matter intake. }, issn = {1176-5283}, author = {Roche JR and Kolver ES and Lee JM and Aspin PW and Burke CR and Taylor P and Napper AR} } @conference {41535, title = {Influence of dairy cow genotype on milksolids, body condition and reproduction response to concentrate supplementation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {46-52}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Responses to supplementary feeding overseas (OS) and New Zealand (NZ) Holstein-Friesian (HF) cows were investigated over two years using 57 cows receiving a high pasture allowance and 0, 3 or 6 kg concentrate DM/cow/day. Cows of similar Breeding Worth ($BW) grazed as a single herd and were individually fed a grain-based supplement. Important production genotype x diet interactions of a scaling nature were detected. Across all supplementation levels, OS cows gave a greater (P < 0.05) linear production response than NZ cows (74 vs 37 g MS/kg concentrate DM; 1.22 vs 0.67 kg milk/kg concentrate DM consumed, respectively), but gave a similar response in live weight and condition score gain during lactation per kg of concentrate DM consumed. However, because OS HF appeared to have a larger relative feed deficit than NZ HF when fed ad libitum on pasture, OS HF maintained a lower body condition score throughout lactation and produced less milksolids (as a \% of live weight). Current supplementary feeding decision rules which recommend reducing supplementary feed use when abundant pasture is available remain appropriate for high $BW NZ HF cows. However, reasonable responses to high-energy supplements will continue to be obtained from high $BW OS HF cows, even when pasture supply appears adequate to meet cow requirements. Use of indicators of relative feed deficit such as milksolids as a \% of live weight and body condition score, may be a better guide to predicting the production response to supplementation, rather than decision rules based on genotype. KEYWORDS: Holstein-Friesian; genotype; supplements. }, issn = {1176-5283}, author = {Kolver ES and Roche JR and Burke CR and Aspin PW} } @conference {41843, title = {Mathematical modelling of anoestrus in dairy cows and the linkage to nutrition}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {324-328}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Postpartum anoestrus is a major reproductive problem in New Zealand dairy cows and its duration is related to the nutrition levels both pre and post calving. However, the mechanistic details of this relationship are largely unknown. A better understanding of the interactions between nutritional status, and the levels of the reproductive hormones controlling follicle development and ovulation is needed. A mathematical model consisting of a set of interactive nonlinear differential equations and describing the dynamics of the interactions among luteinising hormone (LH), follicle stimulating hormone (FSH) and oestradiol was developed. The model depicts oestradiol profiles generated by individual follicles from the first follicular wave after calving until ovulation, and changes in LH pulsatility leading to the first pre-ovulatory surge are also produced. The robustness of the model was ascertained from iterative processes, and it was also checked against existing experimental data so as to mimic observed changes in hormone levels. It was shown that two mathematical parameters which control: i) the speed of changes in the feedback of LH activity to oestradiol; and, ii) the sensitivity of the ovarian response to LH, have the greatest effect on duration of anoestrus. KEYWORDS: mathematical model; anoestrus; dairy cows; nutrition; oestradiol; LH; FSH. }, issn = {1176-5283}, author = {Smith JF and Soboleva TK and Peterson AJ and Pleasants AB and Chagas LM and Burke CR} } @conference {41554, title = {Modelling the effects of zero-inductions on profitability in dairy systems}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {132-136}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Inductions are an animal welfare issue and regulations aim to achieve < 2\% inductions on a national basis by 2010. There is a need to assess the longer-term impacts of alternative reproduction management strategies on farm economics and their success in solving the problem of poor reproductive performance. Dexcel{\textquoteright}s Whole Farm Model was calibrated against observed data from Lincoln University Dairy Farm where 11\% of the herd was subjected to inductions in the 2002/03 season, but a zero-induction policy has since been adopted. Results from one-year simulations over five different climate years showed a significant decrease in farm profit ($105/ha, P < 0.05) from the benchmark farm with 11\% inductions (following {\textquoteleft}best practice{\textquoteright} guidelines) to a farm where the late-calvers were culled and replaced by bought-in early-calving heifers and where stocking rate was raised moderately (< 10\%) to compensate for the higher proportion of heifers in the herd. Multiple-year simulations reflecting carry-over effects showed that a strategy with a 10-week mating period, annual culling of 25\% of the herd including all empties and replacement with synchronized heifers mated to start calving one week before planned start of calving can match the farm profitability of the {\textquoteleft}Induction{\textquoteright} strategy if implemented consistently for 5-8 years. Key words: calving spread; modelling; synchrony; mating; replacement. }, issn = {1176-5283}, author = {Beukes PC and Thorrold BS and Wastney ME and Glassey CB and Burke CR and Van Bysterveldt AM} } @conference {41825, title = {Predicting next oestrous date and drafting automatically milked cows for focused attention on oestrous detection}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {231-235}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {The autumn-calving herd at the Dexcel Automatic milking farm was used to test a system of predicting next oestrous date for individual cows and automatically drafting them for focused observation of behavioural oestrus. During the first 21 days of artificial inseminations (AI), the automatic milking system was programmed to draft cows into a holding paddock on each of three days either side of the due date for next oestrus, which was predicted from oestrous dates and milk progesterone concentrations collected prior to the planned start of mating. Cows drafted into the holding paddock were visually checked in the morning, released if not in oestrus or retained if in oestrus for AI later in the morning. The remainder of the herd was also visually checked for oestrus in the morning and afternoon. During the first 21 days of mating, 29 of the 37 cows (78\%) were inseminated, and 22 (76\%) of these were inseminated within the predicted {\textquoteleft}six-day separation window{\textquoteright}. Of these 22 cows, 15 (68\%) were detected as being in oestrus after being drafted into the holding paddock. A system for drafting cows due to be in oestrus for focused observation is achievable in practice, although improved performance will be necessary to reach the desired level of reliability. KEYWORDS: oestrous detection; automation; dairy cattle. }, issn = {1176-5283}, author = {Burke CR and Davis KL and Jago JG} } @conference {41844, title = {Relationships among metabolic hormones, luteinising hormone and anoestrus in periparturient dairy heifers fed two nutritional levels prepartum}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {329-334}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {A mathematical model that describes the dynamics of reproductive hormones was developed to estimate the duration of the postpartum anoestrus interval (PPAI) in cows. The model identified two relatively separate mechanisms: one influenced PPAI through luteinising hormone (LH) release; and it is suggested that another one controlled ovary sensitivity to LH. Examining the role played by these mechanisms in the relationships between nutrition and PPAI involved analysing the data from an experiment that measured the effects of prepartum nutrition on PPAI in which levels of insulin-like growth factor-I (IGF-I), insulin, glucose, leptin and growth hormone (GH) were recorded. Five months before calving, 30 Holstein-Friesian heifers were randomly allocated to a high (HP) or low plane (LP) of nutrition. Body condition scores at calving were 6.3 and 4.1 for the HP and LP treatments respectively. Both groups were fed ad libitum after calving. Secretion patterns of LH were measured at 2, 5 and 8 weeks after calving. PPAI differed between treatments (HP 62.0 {\textpm} 7.95 days; LP 83.1 {\textpm} 6.95 days; P < 0.05), as did the level of GH at calving (HP 5.8 {\textpm} 1.23 ng/ml; LP 10.3 {\textpm} 1.23 ng/ml; P < 0.001). The within treatment variation in PPAI was partitioned into that associated with LH frequency post calving and that orthogonal to LH pulse frequency. Within each treatment, GH was associated with the LH frequency and insulin was associated with the component orthogonal to LH frequency. These results link nutrition to the PPAI through the dynamics of insulin and GH. KEYWORDS: mathematical model; anoestrus; dairy cows; nutrition; metabolites; LH. }, issn = {1176-5283}, author = {Pleasants AB and Chagas LM and Burke CR and Smith JF and Soboleva TK and Peterson AJ} } @conference {41471, title = {Efficacy of pre-mating supplementation with mono propylene glycol on reproductive performance of cows in commercial dairy herds}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {53-57}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {Prolonged postpartum anoestrous intervals (PPAI) are the major source of infertility in New Zealand dairy cows. Postpartum supplementation with mono propylene glycol (MPG) was previously shown to reduce PPAI in heifers. The present experiment tested this treatment in four large commercial dairy herds. During the six-week period preceding the planned start of mating (PSM; week 0), cows were drenched either once (1xMPG) or twice (2xMPG) daily with 200 ml MPG, or served as untreated controls (CON). Analyses were confined to the group of cows that were anoestrus at Week {\textendash}6 or calved between Week {\textendash}6 and Week {\textendash}4 relative to PSM (n = 662 to 669 per treatment). Change in body condition score between Week {\textendash}6 and Week {\textendash}1(∆BCS), and proportion of cows that were anoestrus at Week {\textendash}1 were influenced by herd, age and time of calving (P<0.05) but not by treatment (P>0.1). Treatment did not influence the proportion of anoestrous-treated cows inseminated after oestrus detection (n =263), or the pregnancy rate among all cows. Pre-mating supplementation with MPG did not influence ∆BCS, the percentage of cows that were anoestrus at Week {\textendash}1, or rates of submission and conception. Change in BCS affected both milk yield and pregnancy rates, where cows that gained BCS produced less milk but showed higher 6-week pregnancy rates. This study highlighted that key factors influencing the percentage of anoestrus at PSM are cow age, time of calving and management of the herd. }, issn = {1176-5283}, author = {Tunon GE and Taufa VK and Burke CR and Holmes CW and Chagas LM} } @conference {40997, title = {Effect of luteolysis on control of ovarian follicles using oestradiol benzoate and progesterone in cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {58}, year = {1998}, month = {Jan}, pages = {89-91}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {This study aimed to determine whether progesterone from intravaginal insertion of a CIDR device could substitute for luteal progesterone and facilitate oestradiol benzoate (ODB)-induced control of ovarian follicle waves in the event of luteolysis. Luteolysis was induced by an injection of prostaglandin-F2a on Day 13 of the oestrous cycle in 24 lactating dairy heifers. Concurrent treatments on Day 13 were: i) 1 mg ODB i.m. (ODB1); ii) CIDR for 6 days (CIDR); iii) 1 mg ODB i.m. plus CIDR for 6 days (ODB1/CIDR); or, iv) 2 mg ODB i.m. plus a CIDR for 6 days (ODB2/CIDR). Examination of the ovaries using ultrasonography showed that oestrous cycles comprising 2 follicle waves predominated among ODB1 and CIDR groups; whereas combination treatments produced mostly 3-wave cycles (p<0.05). Day of ovulation was 15.4 {\textpm} 0.3, 21.2 {\textpm} 0.2 and 22.5 {\textpm} 0.2 for ODB only, CIDR only and 1 or 2 mg ODB plus CIDR cows, respectively (p<0.01). The interval from day of emergence to ovulation of the ovulatory follicle was less (p<0.01) in cows treated with ODB only (6.0 {\textpm} 0.3 days), or ODB plus a CIDR (7.2 {\textpm} 0.6 days), compared to a longer interval in those receiving a CIDR only (11.0 {\textpm} 0.8 days). These results showed that progesterone from a CIDR device was able to facilitate ODB-induced follicle wave turnover at the time of luteolysis in lactating dairy heifers. }, issn = {1176-5283}, author = {Burke CR and Morgan S and Clark BA and Rhodes FM} } @conference {40995, title = {Manipulating patterns of ovarian follicle development in cattle with progesterone and gonadotrophin releasing hormone to produce oestrous cycles with two or three follicle waves}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {58}, year = {1998}, month = {Jan}, pages = {85-87}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {This study tested the hypothesis that oestrous cycles with two follicle waves created using progesterone, could be converted to oestrous cycles with three follicle waves using gonadotrophin releasing hormone (GnRH). Oestrus (Day 0) was synchronised in 24 Friesian cows. On Day 2, a progesterone containing device (CIDR) was inserted into the vagina of 16 cows for 10 days. Eight of these animals received 8{\textmu}g of buserelin (GnRH) at device removal. Eight untreated animals formed the Control group. Daily transrectal ultrasonography showed that the oestrous cycles of the cows treated only with a CIDR device had two ovarian follicle waves compared to 1/8 in CIDR+GnRH and 3/8 in Control groups (p<0.01). The average length of the oestrous cycle was shorter in the CIDR-only group (19.3 {\textpm} 0.5 days), compared to the CIDR+GnRH (20.9 {\textpm} 0.2 days) and Control (22.3 {\textpm} 1.1 days) groups (p<0.05). These results demonstrate that strategic administration of GnRH can convert progesterone induced two-wave oestrous cycles into a three-wave pattern. }, issn = {1176-5283}, author = {Clark BA and Rhodes FM and Burke CR and Morgan SR and Macmillan KL} } @conference {40944, title = {Effect of hormonal environment at emergence on persistence of ovarian follicles in cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {57}, year = {1997}, month = {Jan}, pages = {239-240}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Reduced fertility often occurs when progestins are used to control the timing of oestrus in cattle and is espe-cially evident when a corpus luteum (CL) is not present in the ovary (Kinder et al., 1996). The lowered conception rates at the synchronised oestrus are associated with the development of abnormally large, {\textquotedblleft}persistent{\textquotedblright} ovarian fol-licles as a result of increased secretion of LH. An under-standing of the endocrine regulation of persistent follicles is essential for development of methods to prevent ovula-tion of this aberrant structure in progestin-based oestrous control systems. The influence of time of luteal regression relative to follicle emergence on persistence of dominant follicles was evaluated in progestin-treated cows.}, issn = {1176-5283}, author = {Day ML and Burke CR and Nation DP and Rhodes FM and Macmillan KL} } @conference {40946, title = {Use of pregnant dairy cows in product development of the intravaginal progesterone releasing (CIDR) device.}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {57}, year = {1997}, month = {Jan}, pages = {242}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {This study aimed to confirm that pregnant cows could be used to study release rates of progesterone (P4), the hormone of {\textquoteleft}pregnancy{\textquoteright}, 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.}, issn = {1176-5283}, author = {Burke CR and Burggraaf S and Bunt C and Rathbone M and Macmillan KL} } @conference {40823, title = {An attempt to create an {\textquoteright}anoestrous cow{\textquoteright} model by restricting feed allowances in non-lactating cyclic cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {233-235}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {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 }, issn = {1176-5283}, author = {Burke CR and Verkerk GA and Macmillan KL} } @conference {40822, title = {Hormonal induction of oestrus during the early postpartum period and the subsequent effects of nutrition on ovarian activity in dairy heifers}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {230-232}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {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.}, issn = {1176-5283}, author = {Burke CR and Macmillan KL and Verkerk GA} } @conference {40722, title = {The effect of stocking rate and breed on the period of postpartum anoestrum in grazing dairy cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {236-238}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The effects of stocking rate (low, L; and high, H), breed (Jersey, J; and Friesian, F) and age (2, 3, >3 years old) on the intervals from calving to first ovulation and to first oestrus were assessed in pasture grazed dairy cattle using a 2 x 2 design. Cows in the FH herd had longer intervals from calving to first postpartum ovulation (C-ovn1; 49.2 vs 24.7, 31.1 and 29.4 days) and C-hl (47.1 vs 32.5 days) intervals than older cows, with 3 year old cows intermediate. The high stocking rate herds had reduced CS, liveweight and milk production compared to the low stocking rate herds. Condition score and milksolids production were inversely related to the C-ovnl and/or C-hl intervals. Increased stocking rates were associated with longer periods of postpartum anoestrum. }, issn = {1176-5283}, author = {McDougall S and Burke CR and Williamson NB and Macmillan KL} } @conference {40673, title = {Effects of breed and calving liveweight on postpartum ovarian activity in pasture-fed dairy heifers}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {76-78}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {There is little information available on the muscle biology of deer and how this affects meat quality. The reported effects of the calcium dependent protease system (calpains and their inhibitor calpastatin) on protein turnover in vivo and myofibrillar structure posts mortem suggest it may have a pivotal role in regulating muscle growth and meat tenderisation. This study examines inter-muscle variation in the calpain system under two physiological conditions in red deer and its relation to meat tenderness. Nine muscle samples from 3 stags in rut (IR) and 3 out of rut (OR), were processed for calpain and calpastatin analysis within 20 minutes of slaughter. Tenderness of aged muscles was determined by measurement of ultimate shear force. The majority of the inter-muscle differences in the calpain system were associated with calpastatin activity. A positive relationship between muscle calpastatin levels and meat ultimate shear force was found. }, issn = {1176-5283}, author = {Burke CR and McDougall S and Macmillan KL} } @conference {40402, title = {The effect of pretreatment with progesterone on the oestrous response to oestradiol-17Beta benzoate in the post-partum dairy cow}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {52}, year = {1992}, month = {Jan}, pages = {157-160}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Crossbreeding with Booroola Merino rams was initiated in 1986 in Israel to transfer the FecB allele to the Awassi (Aw) and the Assaf (As) dairy breeds to increase their prolificacy. The prolificacy of the F1 ewes was higher by about 0.6 lambs/ewe lambing (P<0.05) over the prolificacy of Aw and As ewes. Growth rate up to 150 days of age did not differ between As, }, issn = {1176-5283}, author = {McDougall S and Burke CR and Macmillan KL and Williamson NB} }