@conference {75923,
	title = {Feeding behaviour differs between dairy calves selected for divergent feed conversion efficiency},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {71},
	year = {2011},
	month = {Jan},
	pages = {281-285},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Invercargill},
	abstract = {Feeding behaviour and efficiency of feed utilisation, measured as residual feed intake (RFI; defined as actual feed intake minus predicted feed required), were measured in dairy calves aged six to seven months-old, and associations between the two variables were determined. The intake, feeding behaviour, and live weight of 219 female Holstein-Friesian calves were recorded for 46 days. Animals were housed in an outdoor facility comprising 28 pens, each with a single-access feeder containing dried, cubed lucerne. Efficient animals were associated with lower intakes (r{\texttwosuperior} = 0.29), fewer meals/day (r{\texttwosuperior} = 0.05), less time spent eating/day (r{\texttwosuperior} = 0.03), and slower eating rates (r{\texttwosuperior} = 0.03). The 30 most efficient animals consumed less (mean {\textpm} standard error of difference; 6.15 vs 7.46 {\textpm} 0.20 kg cubes/day), had fewer meals (4.03 vs 4.85 {\textpm} 0.29 meals/day), and spent less time feeding (2.68 vs 2.93 {\textpm} 0.11 hours/day) compared to the 30 least efficient animals (all P <0.05). Rate of liveweight gain, eating rate, amount eaten per meal, and meal duration did not differ between the 30 most efficient and 30 least efficient animals (P >0.05). In conclusion, differences in feeding behaviour were found between dairy calves selected for divergence in efficiency which may have implications for their management.},
	issn = {1176-5283},
	author = {Green TC and Waghorn GC and Beausoleil NJ and MacDonald KA}
}
@conference {69476,
	title = {Prediction of herbage dry matter intake for dairy cows grazing ryegrass-based pastures},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {70},
	year = {2010},
	month = {Jun},
	pages = {80-85},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {A model that combines theoretical and empirical equations was developed to predict daily dry matter intake (DMI) for Holstein-Friesian (HF) cows grazing ryegrass-based swards and offered differing levels of concentrate supplementation. An upper limit to potential herbage dry matter (DM) intake at grazing was set, which is the lower of three limits set by either physical (rumen fill), metabolic (energy demand) or grazing restrictions. Potential herbage DMI at grazing and the herbage allowance were then used to predict herbage DMI, of cows fed only pasture, using an empirical algorithm. If supplements are fed, substitution rate was predicted to calculate actual herbage DMI. An independent dataset, with individual herbage DMI measurements (n = 1,147) of three strains of lactating HF cows, was used to validate the model. Data within strains were averaged for every month of lactation, allowing 27 data points for validation. The fitness of the model was satisfactory, with a relative prediction error (RPE) of 0.083 and a concordance correlation coefficient (CCC) of 0.74. Herbage DMI was simulated for HF cows of different genotypes fed different levels of concentrate supplementation at different herbage allowances. The model successfully predicted herbage DMI of grazing cows under different combinations of nutritional, physiological and genetic variables.},
	issn = {1176-5283},
	author = {Baudracco J and Lopez-Villalobos N and Holmes CW and MacDonald KA}
}
@conference {69515,
	title = {Variation in feed conversion efficiency in Holstein-Friesian heifer calves},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {70},
	year = {2010},
	month = {Jun},
	pages = {250-252},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {Feed conversion efficiency (FCE) is a measure of an animal{\textquoteright}s ability to convert feed into product and is a major determinant of profitability in livestock production. This study evaluated two determinants of FCE in Holstein-Friesian heifer calves, growth rate and residual feed intake (RFI). The improvement in FCE, measured as feed intake per unit of liveweight gain (kg/kg), associated with increased growth rate is well known (see Archer et al., 1999). It is measured when the energy costs of maintenance are relatively small compared to the energy intake that is partitioned into growth of animal tissues or lactation.},
	issn = {1176-5283},
	author = {Carnie KR and Davis SR and MacDonald KA and Waghorn GC and Obolonkin VV and Spelman RL}
}
@conference {60935,
	title = {Using an existing intake model to demonstrate relationships between herbage allowance, hunger drive, days in milk and actual intake in grazing dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {69},
	year = {2009},
	month = {Jun},
	pages = {28-31},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {A sheep intake model was adjusted for dairy cows and used to illustrate intake in relation to inherent hunger, days in milk (DIM), and herbage allowance. Intake is predicted by an exponential function of pregrazing herbage mass, stocking density and hunger drive (k). In adjusting the model, k was re-parameterised using a data set of n = 1,198; it was then adjusted to represent intake decline from peak to end of lactation. This adjustment resulted in splitting k into a and b. Parameter a represented inherent hunger and b its persistence during lactation. The re-parameterised model was tested against an independent data set (n = 287). The square root of mean prediction error was 1.57, indicating good prediction accuracy. Data from three different cow strains, New Zealand-70 and -90 and North American-90 (n = 210, 293 and 271, respectively) were used to reestimate a and b, and to illustrate inherent hunger drive. a and b differed (P <0.01) between strains. Then, with the adjusted and re-parameterized models, the interaction effect of herbage allowance, strain, and DIM on intake were simulated. The adjusted model offers an easy-to-use tool to compare, interpret and illustrate feeding scenarios. },
	issn = {1176-5283},
	author = {Gregorini P and Romera AJ and Beukes PC and Rossi JL and MacDonald KA}
}
@conference {41778,
	title = {Indole and skatole as markers for nitrogen utilisation in dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {68},
	year = {2008},
	month = {Jan},
	pages = {23-26},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Brisbane, Australia},
	abstract = {Indole and skatole are products of amino acid degradation in the rumen which could be useful to monitor protein utilisation in grazing ruminants. Two groups ("1970s" strain and "current" strain) of mixed age Holstein Friesian cows were housed indoors and fed cut pasture for 21 days. Concentrations of indole and skatole in milk fat and of milk urea nitrogen were determined. No significant differences were observed between strains of cow for indole and skatole concentration in milk fat, but they were different (P<0.01) between sampling dates. Both indole and skatole had moderate positive (r ~0.50) correlation with the rumen degradable protein (RDP) balance, whilst skatole had a weaker (r ~0.30) correlation with crude protein intake, metabolisable protein supply and RDP supply. Indole and skatole concentrations in milk fat were more closely correlated to the estimated RDP balance in the rumen than milk urea. A large proportion of individual animal variation in milk metabolites remains unaccounted for by protein intake, and may relate to individual differences in detoxification and elimination of indole and skatole. },
	issn = {1176-5283},
	author = {Pacheco D and Lane GA and Fraser K and MacDonald KA and Back PJ}
}
@conference {41989,
	title = {Restricted postpartum feeding in grazing dairy heifers decreases milk production but does not lengthen oestrous interval},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {67},
	year = {2007},
	month = {Jan},
	pages = {255-260},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Wanaka},
	abstract = {The aim of this study was to determine the effects of pasture allowance postpartum on the initiation of ovarian activity, metabolite and hormonal secretion, and milk production. After calving, thirty six HolsteinFriesian heifers (BCS 5.0) received either unrestricted pasture allowance (UNR; n=18) or restricted (RES; 73\% dry matter intake of the unrestricted group;n=18) pasture allowance. The LW was lower (P < 0.05) for the RES group than the UNR group. Body condition score of all heifers decreased after calving in both groups. The mean time to ovulation was similar for UNR 50.0 and RES 50.3 sed. 8.2 days after individual calving date. The daily average from week 2 for milksolids, protein and lactose yield was lower (P < 0.05) in the RES group. Plasma concentrations of insulin were lower (P = 0.0085) in the RES group when compared to the UNR group. Glucose concentrations was lower (P = 0.016) in the RES group. Plasma concentration of NEFA was greater (P = 0.001) in the RES group. There was an interaction with treatment differences decreasing by week 11 and 12 for glucose (P =0.001) and NEFA (P =0.006). Plasma concentrations of leptin (P = 0.013) and IGF-I (P = 0.026) were lower in the RES. No differences, associated with postpartum nutrition, were found for plasma GH. Restricted feeding postpartum had no effect on days to first postpartum ovulation but decreased liveweight, milk production and affected some metabolic hormones during postpartum.},
	issn = {1176-5283},
	author = {Chagas LM and Gore PJS and MacDonald KA and Blache D}
}
@conference {41934,
	title = {Effect of cow genotype and feed allowance on milk composition},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {66},
	year = {2006},
	month = {Jan},
	pages = {397-402},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Napier},
	abstract = {The effect of strain of Holstein-Friesian and level of feed allowance on milk composition, individual milk proteins, and minerals was examined in a seasonal calving pastoral dairying system. The trial included two high genetic merit strains of either North American (OS90) or NZ (NZ90) genetics, and one strain representing NZ 1970{\textquoteright}s genetics (NZ70). Each strain was farmed under systems designed to provide total feed allowances of 4.5 to 7.0 t DM/cow/year. Milk composition was affected by strain of cow and by feed allowance. Strain of cow influenced crude protein (P<0.05), true protein (P<0.01) and casein (P<0.01) concentrations, with the NZ90 and OS90 strains having higher concentrations than the NZ70 strain. Increased feed allowance resulted in increased crude protein (P<0.05), true protein (P<0.05) and casein (P<0.05) concentrations. Strain, but not increased feed allowance affected the protein:fat ratio, with the OS90 strain having a higher ratio (P<0.05) than the NZ strains. Strain altered concentrations of {\'a}-casein (P<0.05), with NZ90 having the highest concentrations and NZ70 the lowest concentrations. No consistent effect of strain or feed allowance was determined on whey proteins except for {\^a}-lactoglobulin (P<0.027), where the OS90 strain had higher concentrations than the NZ strains. No consistent effect of strain or increasing feed allowance was seen on milk mineral concentrations. These results demonstrate that different selection and breeding policies have influenced major milk components which may influence milk processing and product characteristics. },
	issn = {1176-5283},
	author = {Turner S-A and MacDonald KA and Back PJ and Thomson NA}
}
@conference {41572,
	title = {Comparing feed allowances to inferred energy intake using data from a dairy grazing farm trial},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {65},
	year = {2005},
	month = {Jan},
	pages = {225-230},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {The main objective of this research was to investigate whether calculating intake of dairy cows using equations to predict energy requirements provides a good alternative to conventional ways of estimating intake. The method was applied to data from the Dexcel Holstein-Friesian strain trial over three seasons. Feed intake per cow was calculated as the sum of the energy requirements for maintenance, milk production, pregnancy, growth and body tissue mobilisation using measured yields of milk, fat, protein and lactose, live weight and body condition score of cows and calf live weights. In order to compare the estimates of feed intake to the amount of feed offered, linear regressions of calculated (ME) intake (grouped by farmlet) on the amount ME offered per farmlet were performed by season. The relationship between ME intake and ME offered was weak in the first year, with a limited response to increasing the amount of feed offered. This was because all the cows were two-year-olds with lower live weights and milk yields and consequently lower feed intakes. In the subsequent two years of the trial, the relationship between ME intake calculated using the energy equations were 67\% and 72\%. The modern strains of dairy cows responded well to higher levels of feed offered, while the 1970s strain of New Zealand dairy cows failed to increase intake when offered diets of higher total ME. Our results show that energy prediction equations offer a viable and cheap alternative of estimating ME intake of lactating dairy cows.
KEYWORDS: dairy cows; energy intake; strain comparison; efficiency. },
	issn = {1176-5283},
	author = {Pryce JE and Harris BL and Montgomerie WA and Jackson R and MacDonald KA and Glassey CB and Thorrold BS and Holmes CW}
}
@conference {41826,
	title = {Differences in grazing behaviour and herbage intake between genotypes of Holstein-Friesian dairy cows grazing short or long swards},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {65},
	year = {2005},
	month = {Jan},
	pages = {236-240},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {The objective of this work was to compare dry matter intake and grazing behaviour of different strains (S) of Holstein-Friesian dairy cows during early lactation. Three strains of different origin [two 1990{\textquoteright}s genotypes of Holstein- Friesian from Overseas (OS90) or New Zealand (NZ90) origin and a 1970{\textquoteright}s NZ Friesian (NZ70)] were offered low or high pre-grazing herbage mass (HM) (2100 vs 2800 kg DM/ha) at a common daily allowance (35 kg DM/cow) between September and November 2004. Pasture dry matter intake (IT) and digestibility (D) were determined using the n-alkanes methodology. Time spent grazing (GT) and ruminating (RT) were observed for 24 hours. Intake per empty body live weight unit (ILW) and rate of intake (IRATE) were calculated. There was a significant SxHM interaction (P < 0.001) for IT and ILW. IT was similar at low HM across strains, whereas at high HM, a lower IT was recorded for the NZ70 while it was higher for the OS90. At low HM, ILW was slighter lower in the OS90 than in the NZ90 (P = 0.06) while at high HM both NZ90 and OS90 showed a higher ILW. In vivo digestibility was similar across strains but was higher at high HM (P < 0.001). There was a significant SxHM interaction for GT (P < 0.01) with both NZ strains spending more time grazing at low HM, in contrast, GT was similar across strains at high HM. RT was higher for the OS90 strain than for both NZ strains (P < 0.05) and greater at high HM (P < 0.001). There was a significant SxHM interaction for IRATE (P < 0.05) with the NZ90 and OS90 strains showing similar IRATE at low HM but different at high HM. Results indicate a difference in the ability of the strains to adjust their grazing behaviour to different pre-grazing herbage mass.
KEYWORDS: Holstein-Friesian; high-merit dairy cow; intake; grazing behaviour, herbage mass. },
	issn = {1176-5283},
	author = {Rossi JL and MacDonald KA and Thorrold BS and Hodgson J and Holmes CW}
}
@conference {41539,
	title = {Economic comparison of Holstein-Friesian strains},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {65},
	year = {2005},
	month = {Jan},
	pages = {68-73},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {The objective of this research was to identify major determinants of net profit per cow. Data were from the Dexcel strain trial over three seasons, in which Holstein-Friesian cows were managed in groups of 12 to 20 cows in eleven farmlets. Milk returns were calculated from lactation yields of milk, fat and protein. Net profit per cow was calculated as the net return from milk sales plus sales of calves minus feed, fertility, health, shed and working expense costs. Annualised present values were derived using asset replacement theory and discounting to account for different numbers of years of data according to the year in which an animal entered the herd. Net replacement costs and average replacement returns were included where animals were replaced before the end of the trial. Partition analysis was used to identify indicators of cow profitability. Partition analysis recursively sub-divides data creating a tree of partitions. Each split is chosen to maximise the difference in profitability between branches of the split. Variables on which data could be partitioned included breeding values, Breeding Worth and traits measured in first parity. The key determinants of profitability were lactation yield of protein and fat, percentage of fat and Breeding Worth. When these variables were fitted to a multiple regression model where the response was annualised present value, the adjusted R2 was 52\%.
KEYWORDS: asset replacement model; economics; dairy cattle. },
	issn = {1176-5283},
	author = {Pryce JE and Harris BL and Glassey CB and Montgomerie WA and Jackson R and MacDonald KA and Thorrold BS and Holmes CW}
}
@conference {41534,
	title = {Impact of farm management decision rules on the production and profit of different strains of Holstein-Friesian dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {65},
	year = {2005},
	month = {Jan},
	pages = {40-45},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Management decision rules ({\textquoteleft}old{\textquoteright} rules) have been used at the Dexcel No. 2 Dairy Farm to remove subjectivity from the management of farm systems research and have also been promoted to the dairy industry. A trial involving these rules where three strains of Holstein-Friesian (HF) cows were compared has completed its third season. The trial included two high breeding worth (BW) strains of either North American (OS90) or New Zealand (NZ90) genetics, and one low BW strain of NZ genetics (NZ70). Under the {\textquoteleft}old{\textquoteright} rules the OS90 cows had fewer days in milk than the other two strains, mainly because they were dried off earlier due to their lower body condition score (BCS). In the third lactation {\textquoteleft}new{\textquoteright} rules were applied that allowed cows at the higher feed allowances to be dried off later (but at the same BCS) than would have been allowed under the {\textquoteleft}old{\textquoteright} rules. For the herds receiving the higher feed allowances, this change resulted in increased days in milk (NZ90 + 2 days; OS90 + 17 days) more milksolids (MS) per cow (NZ90 +2 kg; OS90 +21 kg), and more feed required (NZ90 + 10 kg; OS90 + 157 kg DM/cow) with all herds reaching target BCS by their next calving. It is calculated that this reduced the difference in economic farm surplus (EFS) per ha between the NZ90 and OS90 from $488 to $219. These results indicate the need to alter management rules to get the best performance from North American HF genetics.
KEYWORDS: Holstein-Friesian; body condition score; drying-off decision rules. },
	issn = {1176-5283},
	author = {MacDonald KA and Thorrold BS and Glassey CB and Holmes CW and Pryce JE}
}
@conference {41568,
	title = {Modelling dairy system efficiencies},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {65},
	year = {2005},
	month = {Jan},
	pages = {203-208},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {The Dexcel Whole Farm Model (WFM) is being developed to simulate dairy systems based on the interaction of system components. The WFM was fitted against observed data from the Resource Efficient Dairying (RED) trial, Scott Farm, Hamilton (Treatment A, 2002/2003 season) and used to explore the effects of different stocking rates on measures of system efficiency, i.e. feed utilisation (FU) and feed conversion efficiency (FCE). At the same stocking rate as RED treatment A (3 cows/ha), and with the observed {\textquoteleft}bestpractice{\textquoteright} management principles in place, the WFM predicted a FU 7\% higher compared with the observed (73\% vs 66\%). Increasing stocking rate in the WFM resulted in an increase in FU, but the predicted FCE did not decrease as was expected. The model showed the importance of adhering to proven management principles to reduce feed wastage and thereby improve system efficiencies.
Key words: stocking rate; simulation modelling; pasture utilisation; dairy farm. },
	issn = {1176-5283},
	author = {Jensen RN and Beukes PC and Clark DA and MacDonald KA}
}
@conference {41511,
	title = {Milk production and grazing behaviour during early lactation of three strains of Holstein-Friesian dairy cows managed in different feeding systems},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {64},
	year = {2004},
	month = {Jan},
	pages = {232-236},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {The objective of this work was to compare individual intake and grazing behaviour of different strains of Holstein-Friesian dairy cows. Strains tested were high breeding worth 1990{\textquoteright}s Holstein-Friesian of overseas (OS90) or NZ origin (NZ90), and a 1970 NZ strain of Friesian (NZ70), farmed under different feeding systems defined by feed allowance per cow per year. Feed allowance ranged from 4.5 to 7.0 t DM cow-1 year-1, based on different stocking rates and supplement inputs. Each system (one strain at one total annual allowance) was managed using a common set of decision rules and all the strains were in similar body condition score (BCS) at calving. Milksolids production, liveweight and BCS were measured routinely, and during September 2002 (55-75 days in milk) daily DMI and digestibility (DMD) were estimated for each cow by the n-alkane method. Grazing behaviour was observed visually.
Daily milksolids yield (per cow and per 100 kg LW) were similar for NZ90 and OS90, which were higher than NZ70 (p<0.01). At the start of the season OS90 cows were heavier (p<0.05) than cows of the other two strains and NZ90 cows heavier (p<0.05) than NZ70 cows, however they were similar in BCS. During September OS90 cows were just slightly heavier than the other two strains (p=0.16), but with lower BCS (p<0.01). Between the start of the season and September, LW and BCS decreases for OS90 cows were significantly higher (p<0.05) than for cows in the other two strains. Slightly higher DMI (per cow and per 100 kg LW) were recorded for the NZ90{\textquoteright}s than for NZ70 and OS90. Grazing time, ruminating time or biting rate was similar across strains. These results suggest that the OS90 was not able to eat sufficient pasture and used more body energy reserves to produce similar MS yield as NZ90. },
	issn = {1176-5283},
	author = {Rossi JL and MacDonald KA and Thorrold B and Holmes CW and Matthew C and Hodgson J}
}
@conference {41409,
	title = {Evidence of a genotype by feeding level interaction in grazing Holstein-Friesian dairy cattle at different stocking rates},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {63},
	year = {2003},
	month = {Jan},
	pages = {73-76},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Queenstown},
	abstract = {Lactation yields and estimated breeding values (EBVs) for protein, fat and milk were obtained for individual cows in a farmlet trial carried out at Dexcel in Hamilton, using Holstein-Friesian cows, to test for the existence of a genotype by environment interaction across the range of feeding levels, and EBVs typically found on New Zealand pasturebased dairy farms. At very low levels of feeding, with yields of 267 - 307 kg milksolids per cow (kg MS/cow), regression coefficients of lactation yield on EBVs were not significantly different from the expected value of 1. At high levels of feeding, with yields of 383 - 411 kg MS/cow, most of the regression coefficients for yields of protein, fat and milk on EBVs were significantly greater than 1. The results of this study show that at low levels of feeding the actual differences in production between cows, which differ in EBVs correspond to the actual differences in EBVs, whereas at high levels of feeding the difference in milk yields between genetic groups are greater than the difference in EBVs. This constitutes a form of genotype x environment interaction, in which genotype is measured as breeding values, and has important practical and economic implications for dairy farms, and for the expected value of genetic improvements. },
	issn = {1176-5283},
	author = {Bryant JR and Holmes CW and Lopez-Villalobos N and MacDonald KA and Brookes IM}
}
@conference {41410,
	title = {Postpartum anoestrous intervals and reproductive performance of three genotypes of Holstein-Friesian dairy cattle managed in a seasonal pasture-based dairy system.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {63},
	year = {2003},
	month = {Jan},
	pages = {77-81},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Queenstown},
	abstract = {An extended postpartum anovulatory interval (PPAI) is the major form of infertility in New Zealand (NZ) dairy cattle. Recently, Holstein cows, originating from North American genetic strains (Overseas; OS), have been widely used in NZ. Worldwide, there is concern over an apparent decline in the fertility of Holstein-Friesian dairy cattle. This study determined whether differences existed in PPAI, BCS and parameters of reproductive performance between NZ and OS Holstein-Friesians. One hundred and forty-six records from 88 NZ animals of high genetic merit for milk production (NZH), 81 records from 48 NZ animals of low genetic merit (NZL), and 137 records from 88 OS high genetic merit animals that calved in Years 1 (all two-year-olds) and 2 (two- and three-year-olds) were included. Over both years PPAI in two-year-olds were significantly shorter in OS (20 days shorter) and NZL (12 days shorter) than in NZH animals (P<0.05). Body condition score at calving, and BCS loss from calving to four weeks postpartum were not different between strains. In Year 1 of the study significantly more NZH than NZL or OS 2-year-olds were treated for anoestrus prior to the start of mating (P=0.001). Other measures of reproductive performance did not differ significantly between strains. The differences in PPAI require further investigation. },
	issn = {1176-5283},
	author = {McNaughton LR and Verkerk GA and Parkinson TJ and MacDonald KA and Holmes CW}
}
@conference {41310,
	title = {Effects of time-of-calving on dairy production: a farmlet study},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {62},
	year = {2002},
	month = {Jan},
	pages = {42-43},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {Most dairy cows in New Zealand are calved just prior to spring in order to maximise pasture utilisation. This practice is associated with marked irregularities in the volume and composition of milk supplied to factories, which is a major limitation of seasonally-calving, pasture-based dairying systems. The need to accommodate peak milk flow means that manufacturing plants are underutilised for most of the season. Further, changes to milk composition can make it difficult to manufacture dairy products of high quality during some parts of the season, which necessitates the storage of product to meet out-of-season demand.
Such irregularities are caused by a number of factors, including nutritional factors associated with the changing quality and availability of pasture, and physiological and hormonal factors associated with the stage of lactation of the cows (Auldist et al., 1997). One way of manipulating the lactation curve of the cows may, therefore, be to adjust the time of the year at which calving occurs. A previous study in New Zealand showed that autumn calving herds could be as profitable as spring calving herds (Garcia et al., 1998). In that study, nutritional demands were matched with pasture availability by adjusting stocking rate and feeding varying amounts of pasture and maize silage when required. A premium for winter milk was also applied.
The current study was designed to investigate the effects of calving at four different times of the year on milk production in farmlet systems which were otherwise similar in stocking rate and other farm management variables. },
	issn = {1176-5283},
	author = {Audlist MJ and MacDonald KA and Thomson NA and Coulter M and Lancaster JAS and Penno JW}
}
@conference {41330,
	title = {Managing dairy calves using continuous stocking and sward surface height - a review},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {62},
	year = {2002},
	month = {Jan},
	pages = {124-127},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {The objectives of this review are (i) to examine the role of continuous stocking management in grazing experiments and on farm; (ii) to discuss the measurement of sward surface height; (iii) and to present experimental liveweight gain data obtained from calves continuously stocked from weaning to nine months of age. Sward height can be used as a guide in cultivar evaluations to maintain equal sward conditions between plots and treatments using put-and-take and continuous stocking management. Continuous stocking management can also be used on farm to achieve the recommended liveweight targets for dairy calves. However, further research is needed to determine the optimum sward height for calves. Weaned Friesian dairy heifers continuously stocked from November 2000 to April 2001 at Dexcel, Hamilton, and grazed to a mean sward height of 5 cm, steadily gained 0.8 kg/day, reaching a final mean of live weight of 226 kg at 9 months of age. The average stocking rate over this period was 7.1 calves/ha and the total liveweight gain was 822 kg/ha. These calves achieved the recommended liveweight targets set for replacement dairy heifers. },
	issn = {1176-5283},
	author = {Bluett SJ and MacDonald KA}
}
@conference {41358,
	title = {Salt supplementation of lactating cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {62},
	year = {2002},
	month = {Jan},
	pages = {236-239},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {<p>Increased intensification of dairy production has contributed to a decrease in the sodium (Na) status of soils throughout New Zealand. This decline has the potential to detrimentally affect animal health and production. A trial was established to determine whether milk production responses would be obtained to sodium supplementation of cows receiving about 0.1\% (0.06-0.14\%) Na in pasture. The cows were in mid-lactation and were randomly allocated to either the control group or a group receiving 14 g Na/cow/day. Supplementation with 14 g Na did not increase milk yield or affect milk composition and there was no interaction with stocking rate. Serum Ca, Mg, Na, and Cl concentration were not affected by treatment, but serum K concentration decreased with Na supplementation. In summary: 0.1\% Na in the diet is sufficient for mid-lactation dairy cows producing 10-12 litres milk/cow/day (0.9 kg milksolids/cow/day) and a milk production benefit will not be achieved through Na supplementation.</p>},
	issn = {1176-5283},
	author = {MacDonald KA and Lile JA and Lancaster JAS and Coulter M and O{\textquoteright}Connor MB}
}
@conference {41329,
	title = {A whole-farm model applied to a dairy system},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {62},
	year = {2002},
	month = {Jan},
	pages = {120-123},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {The complex interactions between the biological, physical and management aspects of a farm can be represented mathematically using a computer model. A whole-farm model has been developed that links published sub-models for cow metabolism together with climate-driven pasture models, in a framework that allows for different management options. The model framework is written in VisualWorks Smalltalk, with submodels written in several programming languages linked to the framework using Microsoft COM protocol. Predictions of the whole-farm model have been compared with pasture and animal production data obtained from a dairy system trial at Dexcel in the Waikato. The system consisted of a herd of 19 cows, at a stocking rate of 3.2 cows/ha. The Whole Farm Model was used with Baldwin{\textquoteleft}s MOLLY cow model of metabolism, the McCall (1984) model of pasture growth, daily climate data and a management policy whereby daily activities on the farm were enacted by the framework. These activities included, for example, assignment of paddock for grazing, closure and cutting of paddocks for conservation, calving and drying off dates of each cow, and supplement feeding. At the end of each season the whole-farm model predicted 75\% of pasture growth compared with observed values assessed by visual assessment, 98\% of milk yield and 98\% of cow live weight. In addition to annual production by the whole farmlet, the whole-farm model can simulate individual animal and paddock production on a monthly and daily basis, so that patterns of change can be compared over the whole season. The whole-farm model is being used as a tool to design and analyse new dairy farm systems. },
	issn = {1176-5283},
	author = {Wastney ME and Palliser CC and Lile JA and MacDonald KA and Penno JW and Bright KP}
}
@conference {41294,
	title = {Adapting the MOLLY cow model to fit production data from New Zealand animals},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {234-236},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {To assist in the planning of farm systems trials, Dexcel is developing a computer model of a pasture-based, rotationally grazed dairy system. The model includes published component models (or submodels) for cow metabolism and pasture growth, as well as climate and management information. It is currently being evaluated against production data obtained from the Whole Farm Efficiency Trial at Dexcel No 2 Dairy. The cow component being used is MOLLY, a dynamic model based on the underlying processes of ruminant digestion and metabolism. The parameters of MOLLY are based on animals that are efficient on high-energy diets. To make the computer model more accurate as a predictive tool for use in NZ, some of the parameters of the MOLLY submodel have been adjusted to fit the production data of NZ dairy cows on pasture, namely bodyweight changes and daily milk yields. MOLLY initially under-predicted by approximately 20\% the body weight of older cows (>4 years) for the pre-calving and early lactation periods. Resetting some parameters in MOLLY significantly improved the prediction of these bodyweight changes: to 2\% for the pre-calving period and 14\% for early lactation. Milk yield per cow was under-predicted in early lactation by MOLLY but the fit for each cow was improved by entering the observed peak daily milk value, although further fitting is required. We conclude that MOLLY is suitable for use as a research tool to gain insights into changes in metabolism of NZ cows grazed on pasture.},
	issn = {1176-5283},
	author = {Palliser CC and Bright KP and MacDonald KA and Penno JW and Wastney ME}
}
@conference {41272,
	title = {Magnesium supplementation of lactating dairy cows in the summer and autumn},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {148-151},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {A series of three trials were established with 188 lactating dairy cows which were supplemented daily with either 0, 10 or 20 g Magnesium (Mg) during 18 weeks from January to May. Cows in each trial were allocated to treatments randomly in a cross-over design with each treatment lasting 2 weeks. This design was replicated three times during the 18 weeks. There was no treatment effect on serum Mg or milksolids (MS) production, (0.82, 0.82 \& 0.83 mmol/l or 0.78, 0.79 \& 0.77 kg MS/cow/day for 0, 10 \& 20 g Mg, respectively; averaged across all trials) and there were no farmlet-by-treatment interactions. Based on visual assessments of pasture intakes and pasture mineral analysis, mean pasture Mg intakes during all three trials ranged from 23 to 35g Mg/cow/day (SEM 1.14). Urine Mg-creatinine ratio of 50 cows during Trial 3 indicated that the urinary Mg concentration increased linearly with increasing dietary Mg (1.38, 1.87, 2.01 for the 0, 10 and 20 g treatments, respectively; SED 0.175). Trial three results suggest that Mg surplus to requirement was being voided by the cow and that it is unlikely that even at the higher stocking rates, a milk production response to Mg supplementation will occur in the summer/early-autumn period when Mg in diet is >0.18\%. },
	issn = {1176-5283},
	author = {MacDonald KA and Penno JW and Verkerk GA and Jago J and Dow BW}
}
@conference {41244,
	title = {Monitoring adrenal activity in dairy cows under various feeding regimens using faecal glucocorticoid metabolites},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {52-55},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Adrenal activity in cattle can be measured by changes in plasma glucocorticoid concentrations. Cows treated with synthetic adrenocorticotrophic hormone (ACTH) to stimulate the adrenal cortex exhibited elevated plasma cortisol concentrations for 4-5h. Concentrations of faecal glucocorticoid metabolites (FGM) peaked between 8-9.5h after ACTH treatment, 2.5 fold higher than basal (P<0.05) and remained elevated for 13h (range, 11.1-16.1h). Faecal glucocorticoid concentrations were monitored in two strains of Holstein Friesian (HF) dairy cows farmed in New Zealand under two systems: NZ pastoral and North American concentrate-based. The overseas (OS) and New Zealand (NZ) HF were fed a pasture-based diet (Grass) or a total mixed ration (TMR) throughout lactation. Faecal samples were collected on four occasions during lactation. Faecal glucocorticoid concentrations of the cows fed Grass were consistently higher (P<0.05) than cows fed TMR. There was also a significant genotype effect; FGM concentrations of the NZ HF cows were higher than OS HF cows (P<0.05). In a separate study, no obvious trends were evident in FGM in NZ HF grazing pasture at three stocking rates (2.2, 3.2, 4.3 cows per hectare). Measuring FGM can be used to monitor acute adrenal activity in cows, but is more difficult to interpret as a measure of chronic stress. },
	issn = {1176-5283},
	author = {Morrow CJ and Kolver ES and MacDonald KA and Verkerk GA and Matthews LR}
}
@conference {41293,
	title = {Toward a predictive model of supplementary feeding response from grazing dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {229-233},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Many experiments have measured the responses of grazing dairy cows to supplementary feeds, but few have studied the reasons for the large differences in responses between experiments. Data derived from two trials, in which supplementary feeds of either maize grain or a nutritionally balancing ration were offered to cows in early, mid, and late lactation in each of spring, summer, autumn and winter, were used to calculate the marginal milksolids responses to supplements. The data set created was subject to multiple regression analysis in an attempt to quantify the effect of the different variables on the magnitude of the response to supplementary feeds. The factor that was of greatest importance was the relative feed deficit (RFD) of the cows measured by the reduction in milksolids yield (kg MS/cow/day) of the respective control groups that had occurred when the restricted feeding treatments had been imposed. Total marginal milksolids responses were greatest when severe feed restrictions, relative to current feed demand, resulted in large reductions in milksolids yield of the control groups. Total marginal milksolids response increased (P<0.01) by 0.9g MS/MJME offered as supplement per 0.1 kg MS/cow/day RFD. Total marginal milksolids responses also declined (P<0.01) by 0.2 g MS/MJME offered as supplement as pasture allowance increased by 10 MJME/cow/day. },
	issn = {1176-5283},
	author = {Penno JW and MacDonald KA and Holmes CW}
}
@conference {41209,
	title = {The effect of pasture silage quality on milk production and liveweight gain of dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {60},
	year = {2000},
	month = {Jan},
	pages = {253-255},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {Farmers in NZ have recently been encouraged to increase the quality of pasture silage they harvest. However, there was no New Zealand information available to ascertain the benefits of improved silage quality when it was offered as a supplement to grazing cows. Identical twin sets were divided into three groups in the winter, spring, summer and autumn during the 1998/99 season. Each group was offered a low pasture allowance and in addition, were offered 3 kg (winter) and 5 kg (spring, summer and autumn) DM/cow/day, of High, Medium and Low-quality pasture silage (nominally 10.4, 9.4 and 8.3 MJ ME/kg DM, respectively) as a supplement to pasture. In spring, summer and autumn offering a high quality silage increased milksolids yield from 1.57 to 1.78, 1.09 to 1.28 and 0.63 to 0.89 kg/cow/day, respectively (P<0.05) relative to cows offered Low-quality silage. There were no consistent live weight responses due to pasture silage quality. The spring, summer and autumn measured milksolids response can be calculated as having a net return (at $3.50/kg MS) of 6.7, 5.1 and 8.3 cents per MJME/kg DM increase. },
	issn = {1176-5283},
	author = {MacDonald KA and Nicholas PK and Kidd JM and Penno JW and Napper AR}
}
@conference {41116,
	title = {Increasing milksolids production with supplementary feeds},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {59},
	year = {1999},
	month = {Jan},
	pages = {188-191},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Four farmlets were established at a stocking rate of 4.41 Friesian cows per hectare to compare rolled maize grain, maize silage and a nutritionally balanced ration as supplementary feeds for grazing dairy cows, for three complete seasons. Supplements were offered whenever it was estimated the herds were eating less than 15 kg DM/cow/day or were leaving a post-grazing residual herbage mass of less than 1800 kg DM/ha. Offering 1.3 to 1.5t DM/cow/year of supplement increased net herbage accumulation from 18.3 to 19.2 t DM/ha, however, this did not result in higher annual herbage intake. The use of rolled maize grain, maize silage, and balanced ration supplements increased production from 1188 kg milksolids (MS)/ha to 1763, 1602, and 1769 ({\textpm}69.6) kg MS/ha/year, with responses of 98, 77, and 99 g MS/kg DM, respectively. The magnitude of the response to the supplementary feed was directly proportional to the increase in metabolisable energy supplied by the supplement. Full lactation responses to supplementary feeds were two fold greater than those measured in short term feeding trials. Responses of 7.5g MS/MJME can be expected over the complete lactation when supplements are offered to dairy cows grazing restricted pasture. },
	issn = {1176-5283},
	author = {Penno JW and McGrath JM and MacDonald KA and Coulter M and Lancaster JAS}
}
@conference {41113,
	title = {Validation of body condition scoring by using ultrasound measurements of subcutaneous fat.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {59},
	year = {1999},
	month = {Jan},
	pages = {177-179},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Visual assessment of body condition score (BCS) is used to aid individual cow and herd management, but the assessment is subjective and does not estimate actual body tissue reserves. Ultrasound (US) measurements of external fat reserves may be more objective. To quantify fat reserves at differing BCS{\textquoteleft}s, fat depth was measured by US on 87 mixed aged Friesian dairy cows on 6 occasions during a year. The US measurements were made at the 12th rib (RIB) and mid-way between the hip and pin bones (HIP). Animals were weighed (LW) and their BCS assessed visually at the same time. Mean BCS was greatest in early summer at 4.5 and lowest in late summer at 3.6. Mean RIB varied from 2.2 mm in mid spring to 3.6 mm in early winter, while mean HIP varied from 1.6 mm in early summer to 4.2 mm in early winter. Changes in BCS and LW were positively correlated. Age and growth in 2 year old animals did not appear to affect this relationship. BCS was positively correlated to both RIB and HIP fat depth. The correlation coefficient varied with time, being smallest in late summer (r = 0.37 \& 0.26 for RIB \& HIP respectively) and greatest in late lactation (r = 0.69 \& 0.82 for RIB \& HIP respectively). The ability of RIB \& HIP measurements to predict BCS was low when BCS was <4.5, but predictability increased as fat depth and body condition increased. Cows at lower scores may deposit or deplete fat internally while having few external fat deposits. Because large changes in liveweight (LW) occurred without changes in BCS, or US, it is possible that fat deposits are internal or intramuscular rather than subcutaneous, and therefore not detectable from external inspection. Since most BCS values are <4.5 for lactating cows, the value of ultrasound to assess fat depots in lactating dairy cows is limited; however it may be of some value with cows of BCS >4.5. },
	issn = {1176-5283},
	author = {MacDonald KA and Verkerk GA and Penno JW}
}
@conference {41001,
	title = {Balancing pasture and maize silage diets for dairy cows using urea, soybean meal or fishmeal},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {58},
	year = {1998},
	month = {Jan},
	pages = {102-105},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Four treatment groups of 10 Holstein-Friesian cows were established at the DRC No. 2 dairy in the spring, summer and autumn of 1996/97 to test the efficacy of providing urea, soybean meal or fishmeal supplement to overcome the protein deficiency that occurs when cows are supplemented with large amounts of maize silage.  Pasture allowance was manipulated to achieve an average pasture dry matter (DM) intake of 6.6kg/cow/day for each group.  Treatment groups were supplemented with 75 MJ ME/cow/day as either 7.0kg DM of maize silage, 7.0kg DM of maize silage plus 90g of urea,  5.2kg DM of maize silage plus 1.4kg DM of soybean meal, or 5.8kg DM of maize silage plus 1.0kg DM of fish meal.  The addition of urea as a source of non-protein nitrogen had no effect on milk, milkfat or milk protein production.  Soybean meal increased milk protein production by 0.06kg/cow/day in both summer and autumn (P<0.01). Fishmeal increased milkfat production by 0.07 (P<0.01) and 0.08kg/cow/day (P<0.05) in summer and autumn and increased milk protein by 0.06 (P<0.01), 0.10 (P<0.01) and 0.08kg/cow/day (P<0.001) in spring, summer and autumn, respectively.},
	issn = {1176-5283},
	author = {MacDonald KA and Penno JW and Kolver ES and Carter WAC and Lancaster JAS}
}
@conference {41004,
	title = {The effect of stage of lactation and season on milksolids response to supplementary feeding of dairy cows.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {58},
	year = {1998},
	month = {Jan},
	pages = {113-116},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {A factorial design was used to determine the effect of offering cows (n=8) in early, mid, and late lactation 50 MJME/cow/day of rolled maize grain (T2) or a nutritionally balanced supplement (T3) in spring, summer, autumn and winter at a restricted pasture allowance. The average milksolids production of the early, mid and late lactation groups was 1.16, 1.10, and 0.96 kg MS/cow/day ({\textpm} 0.013), respectively. When compared to a non-supplemented control (T1), offering T2 and T3 supplements increased MS production from 0.91 to 1.14 and 1.13kg MS/cow/day (P<0.01), respectively. The milksolids responses to T2 was 150g MS/cow/day greater in summer and winter than in spring and autumn (P<0.05). Stage of lactation, or form of supplement, had no effect on milksolids response (P>0.05). These results suggest that the milksolids response to supplementary feeding was determined by the extent supplementary feeding increased total ME intake. },
	issn = {1176-5283},
	author = {Penno JW and Holmes CW and MacDonald KA and Walsh BJ}
}
@conference {41009,
	title = {Management decision rules to optimise milksolids production on dairy farms},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {58},
	year = {1998},
	month = {Jan},
	pages = {132-135},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {A review of grazing management research has provided a series of decision rules for the management of seasonal calving pastoral dairy farm systems. These rules have been used at the DRC No. 2 Dairy to remove subjectivity from the management of farm systems research. Cows are dried off with sufficient time for second calvers and mixed age cows to achieve condition scores of 5 and 4.5 by 1 June. Target pasture average herbage mass at calving is 2200 kg DM/ha. Optimum grazing management during autumn/winter, spring and summer has been shown to increase milksolids production by 29, 70 and 41 kg MS/ha, respectively. Grazing management during late spring must meet the dual objectives of generously feeding the herd, while maintaining pasture quality. Conserved pasture supplements should be fed in late autumn/early winter to meet cow condition, grazing management, and herbage mass objectives. Substantial increases in animal productivity can be achieved by sound farm management during periods of feed deficit. },
	issn = {1176-5283},
	author = {MacDonald KA and Penno JW}
}
@conference {41005,
	title = {Using nitrogen fertiliser to increase dairy farm profitability},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {58},
	year = {1998},
	month = {Jan},
	pages = {117-120},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Five farmlets were established to investigate the profitability of using nitrogen fertiliser (N) to increase pasture supply and milksolids production. Farmlets were stocked with 3.34 (low) or 4.42 (high) Friesian cows/ha and received 0, 200 or 400 kg N/ha/year. Total annual pasture production was increased by 1.76 and 0.97 t DM/ha when 200 kg N/ha was applied and by 3.2 and 3.6 t DM/ha using 400 kg N/ha at the low and high stocking rate, respectively. Annual milksolids production increased by 142 and 218 kg MS/ha after the application of 200 and 400 kg N/ha, respectively. Increasing stocking rate from 3.34 to 4.42 cows/ha reduced milksolids production by 99 kg MS/cow. Applying 200 kg N/ha at the lower stocking rate increased economic farm surplus by $148/ha. Increasing stocking rate reduced total milksolids production and profitability at both rates of N. },
	issn = {1176-5283},
	author = {McGrath JM and Penno JW and MacDonald KA and Carter WA}
}
@conference {40919,
	title = {The effect of level of feeding during rearing on the first lactation milk yield of Friesian replacement heifers.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {57},
	year = {1997},
	month = {Jan},
	pages = {176-178},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Six nutritional regimes were imposed on Friesian heifers (n=270) from weaning to 22 months of age to determine the effect of level of feeding during rearing on subsequent milk production. Nutritional treatments resulted in groups weighing 480, 406, 455, 376, 398, and 342 kg (P<0.05) at 22 months of age. However, once the heifers entered the herd differences liveweight were lost. By 28 months of age the difference between the heaviest and lightest treatment groups was only 44 kg (P<0.05). Level of feeding from 90 to 200 kg liveweight had no effect on subsequent milkfat or protein yield (P>0.05). Heifers offered a high feeding level after 200 kg produced 9.6 kg more milkfat (P<0.01) and 6.6 kg more protein (P<0.01) than heifers offered the low feeding regime. These data suggest that Friesian heifers produce an additional 0.12 kg MS over their first lactation for each additional 1 kg liveweight gained during rearing. },
	issn = {1176-5283},
	author = {Penno JW and MacDonald KA and Bryant AM}
}
@conference {40920,
	title = {Growth of friesian calves offered three allowances of milk replacer.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {57},
	year = {1997},
	month = {Jan},
	pages = {179-181},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {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. },
	issn = {1176-5283},
	author = {MacDonald KA and Penno JW}
}
@conference {40832,
	title = {Effect of body covers on the liveweight gain of heifer replacement calves and yearlings, and the liveweight gain and milksolids production of dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {266-269},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {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 (},
	issn = {1176-5283},
	author = {MacDonald KA and Penno JW}
}
@conference {40824,
	title = {Effect of nitrogen fertiliser and supplements on pasture production and milksolids yield from dairy farm systems},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {236-238},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {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. },
	issn = {1176-5283},
	author = {Penno JW and Bryant AM and MacDonald KA}
}
@conference {40669,
	title = {Effect of nitrogen fertiliser and summer rotation length on milk production in a dry Waikato summer.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {55},
	year = {1995},
	month = {Jan},
	pages = {64-66},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Muscling is considered important by the New Zealand meat industry.   As Texel cross lambs contain more muscle than most other sheep genotypes,   a muscling trial was undertaken using Texel and Oxford cross and High   Romney mixed sex lambs. Eighteen lambs were slaughtered from each   breed. The muscle, bone, subcutaneous and intermuscular fat were separated   from the leg and shoulder of the 54 right sides. The leg comprised on   average 64.4\% lean in the High Romneys, 66.2\% in the Oxford cross lambs   and 67.4\% in the Texel cross lambs (p<0.05). The corresponding figure for   shoulder lean 58.8\% (Romney), 59.9\% (Oxford) and 62.1 (Texel) (p<0.05).   The eye muscle area (cm2) for these lambs was 9.8 (Romney), 11.0 (Oxford)   and 11.7 (Texel). The muscle:bone ratio (weights) for 4 leg muscles to the   femur were 7.0 for the Romneys, 7.6 for the Oxford and 8.3 for the Texel   cross lambs (p<0.10). Only 2 non Texel lambs were classed E under the   European classification system.   },
	issn = {1176-5283},
	author = {Penno JW and Bryant AM and Carter WA and MacDonald KA}
}
@conference {39931,
	title = {Comparative dairy production of Jersey and Friesians},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {45},
	year = {1985},
	month = {Jan},
	pages = {7-12},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Reasons for a temporary infertility syndrome in pasture-fed dairy cows were sought. Low submission and conception rates in 35 mature Friesians (either of high or low breeding index) were associated with low plasma albumin and glucose concentrations at the commencement of mating and poor body condition prior to calving. Discriminant function analysis indicated that albumin concentration was the most important variable in the allocation of cows to "fertility" groupings. Breeding index and level of milk production were relatively unimportant. A disturbance in protein metabolism was implicated as the cause of the infertility syndrome. A concentrate supplement containing 19\% crude protein, fed to monozygous twin cows at 1.4 kg/d for 3 weeks prior to mating led to a marked improvement in conception rate.},
	issn = {1176-5283},
	author = {Bryant AM and Cook MAS and MacDonald KA}
}
@conference {39937,
	title = {Effects of varying feeding time on diurnal calving patterns in dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {45},
	year = {1985},
	month = {Jan},
	pages = {35-38},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Season has important effects on reproduction in cows, although they may ovulate throughout the year. During winter, the effects of season delay puberty, prolong post-partum anoestrus and reduce fertility. There are seasonal differences in gonadotrophin secretion, pre-ovulatory follicular development and corpus luteum function. Furthermore, effects of season are more likely to be expressed when factors such as nutrition, age and lactation limit reproduction performance. Significant interactions occur between season and nutrition in the onset of puberty and the length of the post-partum anoestrous interval. In the pasture-based agricultural system in New Zealand, minimum feed supply occurs in winter when season depresses cow reproductive performance. A concentrated calving pattern is essential to improve feeding management and herd performance. To maintain a concentrated calving and high weaning percentage, calving date must be adjusted to reduce the effects of season and improve herd nutrition.},
	issn = {1176-5283},
	author = {Macmillan KL and Pearce MG and Copeman PJA and MacDonald KA and Kilgour R}
}
@conference {39831,
	title = {Relationships between amount of feed on the farm, autumn-winter grazing management and dairy cow performance},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {43},
	year = {1983},
	month = {Jan},
	pages = {93-96},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {A selection experiment which has resulted in dairy cows of extremes susceptibility to bloat is reviewed. The low susceptibility cows had a higher liquid milk production and a lower milkfat percentage than the high susceptible ones. They showed little or no bloat on highly potent pastures. Comparison of the herds was directed towards physiological differences and relationships which could explain the origin of low susceptibility and lead to phenotypic definition useful for selection. Some differences were found in proportions of salivary proteins and progress has been made in their separation, definition and measurement. In vitro experiments have not indicated sufficient differences in gas or foam production per litre of rumen fluid to explain bloat grade variation but observation followed by direct experiment has shown that a greater volume of rumen fluid is associate4d with a high susceptibility to bloat. This could form a basis for commercial selection if appropriate measurement methods can be devised.},
	issn = {1176-5283},
	author = {Bryant AM and MacDonald KA}
}
