@conference {69516,
	title = {Application of genomic information in a dairy cattle breeding scheme},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {70},
	year = {2010},
	month = {Jun},
	pages = {253-256},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {Marker assisted selection has been applied in dairy cattle breeding schemes over the last decade with minor to moderate improvements in genetic gain. In most cases, the cost effectiveness of marker assisted selection has been neutral, at best. The completion of the sequencing of the bovine genome in 2006 has generated a large number of single nucleotide polymorphisms that has allowed the application of genomic selection. In addition, the cost of genotyping single nucleotide polymorphisms is considerably lower than microsatellite genotyping. Livestock Improvement Corporation has undertaken extensive genotyping of the sires that have been progeny tested in the last 20 to 30 years. Analysis of these data by Livestock Improvement Corporation researchers has identified combinations of markers that were used to obtain genetic evaluation of bulls from their DNA. By utilising this genomic information, semen from two-year-old sires has been sold to New Zealand dairy farmers. Over the past two years, the genomically selected bulls have accounted for approximately 15 to 20\% of the inseminations. It is expected that selection based on genomic information, termed genomic selection, will increase the rate of genetic gain in New Zealand by 30 to 50\%.},
	issn = {1176-5283},
	author = {Spelman RJ and Arias J and Keehan M and Obolonkin V and Winkelman A and Johnson D and Harris BL}
}
@conference {69460,
	title = {Automatic reading of Kamars for heat detection in dairy herds},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {70},
	year = {2010},
	month = {Jun},
	pages = {8-12},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {Most existing heat detection systems for dairy cattle are labour-intensive requiring manual inspection of 
every animal to maximise submission rates. Our solution is to automate heat detection using Kamar HeatMount 
Detectors and a camera-based recognition system. The goal of our system is to obtain 99\% sensitivity and 
specificity, ensuring that cows that are on heat are rarely missed and over-drafts are kept to a minimum. Trials 
of various camera prototypes have been undertaken over the past three years, most recently during the artificial 
breeding period in the Spring of 2009. Over 70,000 images from four farms were taken during the latest trials; 
these photographs were used to assess the system. When considering photo observations, the fully automated 
system had an error rate less than 1\% across all sites in the latest trial, and reaches our goal of 99\% sensitivity 
and specificity. },
	issn = {1176-5283},
	author = {Hempstalk K and Harris BL and Lopdell TJ}
}
@conference {69529,
	title = {Improving the power of activity-based heat detection using additional automatically captured data},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {70},
	year = {2010},
	month = {Jun},
	pages = {299-302},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Palmerston North},
	abstract = {The purpose of this study was to determine the current performance of activity monitoring devices on New Zealand pasture-based farms and investigate the potential for improved detection using additional automatically captured data. The data consisted of heat events that were assigned from pregnancy diagnosis and mating records, and from milk progesterone levels collected twice weekly during mating period. Daily milk production, milking order, milk flow rate and milk conductivity records were also collected during the mating period. The best single predictor of oestrus was 24 hour milk yield difference (P <0.01) for Herd 1 and normalised milking order (P <0.01) for Herd 2. The normalised pedometer data was the next best predictor of oestrus in both herds (P <0.01). A linear logistic regression model was fitted within each herd. The best model included normalised milk production, milking order, milk flow rate and pedometer variables. Machine learning models with balanced bagging were also fitted to the data. The machine learning models provided a better fit than traditional statistical models. Pedometer data can aid in the detection of cow oestrus, however the power of detection improves significantly with the addition of milk yield, milk flow and milking order data.},
	issn = {1176-5283},
	author = {Harris BL and Hempstalk K and de le Rue BT and Jago JG and McGowan JE}
}
@conference {41762,
	title = {The genetic relationship between heifer and cow fertility},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {67},
	year = {2007},
	month = {Jan},
	pages = {388-391},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Wanaka},
	abstract = {Initial predictors of dairy bulls{\textquoteright} fertility proofs are currently limited to body condition score (BCS), milk yield and success of mating in the first 21 days (PM21) for their two-year-old lactating daughters. The first calving rate trait (CR42) is available after a cow has calved for a second time. Obtaining an earlier indication of fertility would be useful for genetic evaluation purposes. The aim of this study was to investigate the genetic and phenotypic control of heifer fertility in addition to investigating the relationship between heifer fertility and traits already included in the prediction ofthe fertility breeding value. Data were available on LIC{\textquoteright}s Sire Proving Scheme animals born from 1989 to 2003 and included records on 244,453 animals. Using data on the first calving, planned start of calving was defined as the day within contemporary group when greater than 10\% of animals had calved. A multivariategenetic analysis was undertaken with the traits PM21, CR42, BCS and 270-day milk yield recorded in lactating cows, in addition to a heifer fertility trait where success is defined as heifers that calve within21 days from the planned start of calving (CR21). The model fitted to these traits included contemporary group of the milking herd, breed proportions and age at first calving as linear and quadratic effects. The mean CR21 in this dataset was 71\%. Heifers failing to calve within 21 days of the herd{\textquoteright}s planned start of calving for heifers also had poorer fertility in first lactation, with a least-squares-mean of 75.5\% (s.e. 0.2) versus 81.5\% (0.1) for PM21 and 54.2\% (0.22) and 62.4\% (0.1) for CR42. The heritability estimate of CR21 was low (0.012), yet the genetic variation was comparable to other fertility measures. CR21 had a positive genetic correlation with CR42, indicating that CR21 may be a useful early indicator of fertility for use in genetic evaluations.},
	issn = {1176-5283},
	author = {Pryce JE and Harris BL and McNaughton LR}
}
@conference {41760,
	title = {Multiple trait national genetic evaluation for cow longevity},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {67},
	year = {2007},
	month = {Jan},
	pages = {377-381},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Wanaka},
	abstract = {In New Zealand genetic evaluation for cow longevitywas based on a single trait model where the phenotypic record was actual or predicted days survived in the milking herd. Cows which were yet to express their actual longevity received a predicted phenotypic record based on the milk production and liveweight production values, traits other than production (TOP), and fertility breeding values. The prediction equation was a proxy for a multiple trait model. At the time of implementation a full multiple trait model was not computationally feasible. A study was undertaken to investigate the feasibility of developing a full multiple trait model. The multiple trait model has the advantage of incorporating the appropriate genetic relationships among the predictor traits and the longevity traits, as well as allowing different genetic correlations among the individual longevity traits. The first stage of the study was to estimate the genetic correlations among all traits under genetic evaluation and two longevity traits; survival from first to second lactation and first to fifth lactation. Data used for genetic correlation estimation was from first lactation records from the Sire Proving Scheme herds for seasons 1987 to 2005. The two fertility traits, 42 day calving rate and percent mated in the first 21 days, had the highest genetic correlations with the longevity traits, ranging from 0.84 to 0.27. Body condition score, management TOP and the milk production traits had moderate genetic correlations with the longevity traits, ranging from 0.42 to 0.24. Somatic cell score, udder support, udder overall, legs, capacity and dairy conformation had low genetic correlations with the longevity traits but were significantly greater than zero. Four longevity traits, and 9 predictor traits were included in a national genetic evaluation for cow longevity. The 9 predictor traits were chosen from the traits that had significant genetic correlations with cow longevity and contained genetic information that was not already included in other predictor traits. Comparisons between sire breeding values from the single trait model and the multiple trait model show good agreement with a correlation of 0.95 for Animal Evaluation enrolled sires. Investigation of the sire breeding values shows that the multiple trait model puts a greater emphasis on cow fertility than the single trait model.},
	issn = {1176-5283},
	author = {Harris BL and Montgomerie WA}
}
@conference {41761,
	title = {Test-day model for national genetic evaluation of milk production traits},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {67},
	year = {2007},
	month = {Jan},
	pages = {382-387},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Wanaka},
	abstract = {Genetic evaluation for milk, fat and protein yields, using 270-day lactation yields in an across-breed animal model (AM), has been performed in New Zealand since 1996. A new system has been developed to calculate breeding values from herd-test data. In the current AM, a 270-day lactation yield record is calculated based on 1 to 10 test-day records. The environmental effect of herd-test-day (HTD) is removed during the 270-day lactation yield calculation. However, this is done outside the AM, without reference to the genetic level of the HTD contemporary group. A test-day model (TDM) can simultaneously account for the fixed effects such as HTD contemporary groups,and the genetic, permanent environmental (PE) and temporary environmental randomeffects that affect the trait. By including the effect in the model, the TDM allows the environment specific to each test-day to be better taken into account, resulting in an improved accuracy of evaluation. A TDM can accommodate changes in the genetic and PE effects over time by fitting polynomials of time to these effects. A random regression (RR) TDM can accommodate changes in the genetic and PE effects overtime by fitting Legendre polynomials of days in milk (DIM) to these random effects. The RR TDM allows each cow{\textquoteright}s lactation curve to have a different shape. TDM evaluations are more stable than evaluations obtained using 270-day lactations because they account for genetic differences in maturity rate and persistency of lactation. The sire breeding values (BVs) from the TDM were compared to those from the AM. For sires with more than 30 daughters, the correlations between the BVs from the two models were 0.990, 0.988 and 0.990 for milk, fat and protein yields, respectively. The TDM demonstrated improved stability for sires undergoing their widespread proof. There was less variation in the change in BVs for reproof sires from August through to October compared to the AM. The sires that show the greatest change during early reproof under the AM were sires that were outliers for their TDM persistency breeding values for their breed.},
	issn = {1176-5283},
	author = {Harris BL and Winkelman AM and Johnson DL and Montgomerie WA}
}
@conference {41875,
	title = {Body condition score as a candidate trait in the breeding worth dairy index},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {66},
	year = {2006},
	month = {Jan},
	pages = {103-106},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Napier},
	abstract = {Body condition score (BCS) has been proposed for inclusion in the New Zealand national dairy index, Breeding Worth (BW), to account for replenishment of body tissue. Currently, the breeding objectives model positively accounts for body tissue mobilisation (through extra yield), but not the negative cost of replenishing body tissue. Two methods have been proposed: 1) Including BCS directly into BW by calculating and assigning an economic value to BCS and 2) Adjusting liveweight Breeding Values (BVs) for BCS, which would mean that liveweight BVs would be expressed at a constant BCS (indirect method). Energy equations were used to calculate the direct economic value for BCS and included a sensitivity analysis. With an economic weight of $25, the percentage emphasis of BCS in BW would be 3.4\%. Including BCS in BW, either directly or indirectly, had little impact on sire rankings (rank correlations with and without BCS within breed were >0.99) and would only have a small impact on the economic response of BW ($0.02 net /cow/annum) and the improvement in BCS (0.006 BCS units/cow/annum). It is concluded that there would be little benefit to including BCS as an independent trait in BW. Body condition score is already included as a predictor in the genetic evaluation of fertility and breeding values for BCS will be estimated routinely from the fertility model.},
	issn = {1176-5283},
	author = {Pryce JE and Harris BL and Johnson DL and Montgomerie WA}
}
@conference {41876,
	title = {Development of new fertility breeding values in the dairy industry},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {66},
	year = {2006},
	month = {Jan},
	pages = {107-112},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Napier},
	abstract = {This paper provides the basis for a new method for calculating fertility breeding values. The objective of this study was to: firstly, investigate the data extract of mating and calving records from Livestock Improvement{\textquoteleft}s national database to identify improvements, secondly investigate the definition of the fertility trait from percent of calves born from artificial insemination (AI) to 42 day calving rate, and thirdly explore the inclusion of milk production and body condition score information. The overall aim was to improve the accuracy of the fertility breeding values available when a sire{\textquoteleft}s daughters have completed their first lactation (i.e., the time of the sire{\textquoteleft}s first proof). A new procedure for routine national evaluation of these traits is outlined. Results from the new system are given. Possible future enhancements to the new system are discussed. The new method improves the accuracy of the fertility breeding value for first crop sires with 80 daughters from 45\% to 52\%. The inclusion of body condition score and milk production in the calculation of the fertility breeding value improves the response to selection for fertility within breeding worth index by 34\% per annum. The improvement in response to selection is worth 0.18 $/cow/year or approximately $700,000 annually to the dairy industry. },
	issn = {1176-5283},
	author = {Harris BL and Pryce JE and Xu ZZ and Montgomerie WA}
}
@conference {41874,
	title = {Genetics of stillbirth in dairy calves},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {66},
	year = {2006},
	month = {Jan},
	pages = {98-102},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Napier},
	abstract = {The aim of this study was to investigate factors affecting, and estimate variance components of, stillbirth using data collected as part of Livestock Improvement{\textquoteright}s Sire Proving Scheme. Only calves that reached full-term of gestation were considered (i.e. abortions and inductions were excluded). After editing there were 773,904 records on calf-fate collected from 1987 to 2004. The mean incidence of stillbirth was 7.2\%. The fixed effect model fitted to the data included the effects of contemporary group, birth assistance code, the sex of the calf, the gestation length of the dam, whether the dam was primiparous or multiparous and mating type e.g. a Jersey cow mated to a Holstein-Friesian sire etc. Breed proportions of New Zealand (NZHF) and North American (OSHF) origin Holstein-Friesian and Jersey were also fitted in addition to the proportion of heterosis expected in the calf. Data were analysed by considering stillbirth as a binomial trait using the logit transformation in ASReml that included a sire-maternal-grandsire pedigree. The direct heritability of stillbirth was estimated to be 0.010 (s.e. 0.009). It was not possible to estimate the maternal heritability using this dataset. Estimates of fixed effects were obtained from ASReml by analysing stillbirth as a continuous trait, as back-transformed fixed effect estimates obtained using a binomial model are unreliable when the incidence is small. The largest effect on the probability of stillbirth was calving difficulty. Compared to no assistance at calving, the two categories of greatest calving difficulty resulted in 22\% and 41\% mortality. The next largest effect on stillbirth was gestation length, with longer gestations being associated with more stillbirths. Males were 1\% more likely to be stillborn than females. OSHF were most likely to be stillborn, followed by Jerseys and then NZHF. Heterosis effects were significant and favourable, except between the two strains of Holstein-Friesians where there was no significant heterosis. The largest heterosis estimate was between NZHF and Jerseys. Unlike some overseas programmes, genetically selecting for reduced stillbirths would not be effective in New Zealand, crossbreeding and devising strategies to manage calving assistance and gestation length appear to be more worthwhile. },
	issn = {1176-5283},
	author = {Pryce JE and Harris BL and Sim S and McPherson AW}
}
@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 {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 {41838,
	title = {Estimation of lactation persistency in crossbred grazing dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {65},
	year = {2005},
	month = {Jan},
	pages = {300-305},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Lactation persistency is commonly referred to as the rate of decline in daily yield after the peak of lactation and can be measured in different ways. The objective of this study was to calculate different measures of persistency for milk traits and estimate the correlations between parameters of the lactation curve in crossbred cattle. Herd test records of milk, fat, protein and lactose from 810 first lactation cows were used to obtain individual lactation curves using a mixed model fitting six knots splines. The model included the fixed effects of contemporary group (year-calving week), sire, age at calving (linear and quadratic) and an average spline and the random effect of cow-spline interaction. All cows were in their first lactation, second cross Friesian x Jersey from a crossbreeding experiment established for quantitative trait loci identification. Persistency was measured in three different ways: P1, slope of the line fitted using linear regression of daily yield on day of lactation from day 60 to day 220; P2, the area under the lactation curve from day 121 to 180 divided by the area under the curve from day 1 to 60; and P3, the 240-day lactation yield divided by peak yield multiplied by 240. Correlations between measurements of persistency ranged from 0.24 to 0.81 and were significantly different to zero (P < 0.001). Correlations between lactation yield and measurements of persistency ranged from -0.43 to +0.33 and were significantly different to zero (P < 0.01). These results indicate that measurements of persistency are not invariant and highlight the need to calculate persistency in a more consistent way. When cows were classified for persistency P2 of fat plus protein, cows of high persistency (top 25\%), compared with cows of low persistency (bottom 25\%), had significantly (P < 0.05) more days in milk, higher total yields of milk and its components, lower peak yields, later day of peak yield and lower rate of decline in daily yield from day 60 to day 220 (P1), but similar 240-day total yield of fat and protein. Farming cows of high persistency may be an alternative to reduce farm investments in peak notes and risks of metabolic problems and reproductive failures.
KEYWORDS: lactation persistency; milk yield. },
	issn = {1176-5283},
	author = {Lopez-Villalobos N and Spelman RJ and Harris BL and Stanley G and Harcourt S}
}
@conference {41537,
	title = {National genetic evaluation for somatic cell score},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {65},
	year = {2005},
	month = {Jan},
	pages = {59-62},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {The method for the national genetic evaluation of somatic cell score (SCS) in New Zealand is described. Evaluation was done using a multiple-trait random regression test day animal model. Trait one was the first-lactation SCS record and trait two was the records from the second and third lactations. Third-order Legendre polynomials of days in milk were fitted to the genetic and cow effects. The evaluation was done across breed. In the first national evaluation, the pedigree contained 15.9 million animals. There were 22.7 million first lactation test day records and 35.4 million second/third lactation test day records. Solutions were obtained using a preconditioned conjugate gradient solver and iteration on data. The resulting breeding values (BVs) indicate a small annual increase (0.01 to 0.03 genetic standard deviation units) in SCS. The range in sire BVs indicate the potential to select for decreased SCS.
KEYWORDS: somatic cell score; genetic evaluation; test day model; dairy cows. },
	issn = {1176-5283},
	author = {Harris BL and Winkelman AM and Montgomerie WA}
}
@conference {41488,
	title = {Genetic and phenotypic relationships between milk protein percentage, reproductive performance and body condition score in New Zealand dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {64},
	year = {2004},
	month = {Jan},
	pages = {127-131},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {Recent research from the Australian In-Calf and New Zealand Monitoring Fertility projects have demonstrated that low milk protein percentage in early lactation is phenotypically linked to poor reproductive performance. The purpose of this study was to quantify the phenotypic and genetic relationship between body condition score (BCS), protein percentage (and other milk production traits) and the reproductive measures used to predict the female fertility breeding value in New Zealand{\textquoteright}s Animal Evaluation System: probability of mating in the first 21 days of a herd{\textquoteright}s mating period (PM21) and the probability of having a calf born to AI (CAI). Data on 99,870 first lactation cows, recorded as part of Livestock Improvement{\textquoteright}s and Ambreed{\textquoteright}s progeny test schemes were used for both a phenotypic analysis and to estimate genetic parameters. Effects of breed, heterosis, BCS, protein percentage and dairy conformation were statistically significant in logistic regression analyses on both CAI and PM21. Genetic correlations between protein percentage and PM21 and CAI were 0.18 and 0.20 respectively and genetic correlations of BCS and PM21 and CAI were 0.48 and 0.38 respectively. These results show that selection for protein percentage is unlikely to have a large effect on reproductive performance, while BCS is a promising tool to aid in selection for improved fertility. },
	issn = {1176-5283},
	author = {Harris BL and Pryce JE}
}
@conference {41487,
	title = {Mate selection to control inbreeding and maximise farm profit of commercial dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {64},
	year = {2004},
	month = {Jan},
	pages = {122-126},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {The objective of this study was to demonstrate the potential benefits of computerised mate selection in a commercial crossbred dairy herd of 411 cows mated to 10 Holstein-Friesian and 10 Jersey bulls. Mate selection was carried out using an evolutionary algorithm to perform single- or multiple-objective optimisation to maximise farm profit ($/4.5 t DM) and/or minimise inbreeding level of progeny. Restrictions were placed on the total number of mating pairs, the maximum number of matings per bull and per cow. Selection and mate allocation of bulls and cows at random produced progeny with average farm profit of $94 and inbreeding level of 1.70\%. Mate selection applied to maximise farm profit yielded a mating set with an average farm profit of $181 and inbreeding level of 2.07\%. Mate selection applied to minimise inbreeding level selected a mating set with average farm profit of $65 and inbreeding level of 0.03\%. Mate selection applied to optimise farm profit and minimise level of inbreeding with a weighted ratio of 1:1, resulted in a mating set with average farm profit of $176 and inbreeding level of 0.44\%. The results demonstrate that in the short term, inbreeding can be controlled at the same time as maximising farm profit using a computerised mating selection program with multiple-objective optimisation. },
	issn = {1176-5283},
	author = {Lopez-Villalobos N and Harris BL and Pryce JE}
}
@conference {41417,
	title = {Comparison of multivariate statistical methods for the prediction of reproductive performance of Holstein Friesian cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {63},
	year = {2003},
	month = {Jan},
	pages = {112-115},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Queenstown},
	abstract = {The objectives of this study were to predict success or failure at mating (1/0) using information on 168 first lactation dairy cows from the Dexcel Strain Trial. The farmlets were established by allocating heifers from three genetic strains to eleven groups. The groups were managed under a range of feeding systems, ranging from moderate to generous allowances. Measurements were taken on milk, fat and protein yields, liveweight and condition score and variables derived from these used as predictors of success at mating in a series of models. Reproductive measures used for analysis were cows in calf at 42, 49 and 56 days after the planned start of mating. Three statistical methods were used to determine suitable predictive models of success at mating: logistic regression, discriminant analysis and partition analysis. Partition analysis was the best method of prediction. Kappa values, measuring the degree of agreement between observations and predictions ranged between 0.32 and 0.38 for discriminant analysis, 0.41 and 0.44 for logistic regression and 0.70 and 0.74 for partition analysis. The partition analysis produced a set of rules for predicting likely success at mating. Important rules were CS > 4.75 in month three of lactation and calving before week four after the start of calving for the herd. },
	issn = {1176-5283},
	author = {Harris BL and Pryce JE and Verkerk G}
}
@conference {40762,
	title = {Across breed evaluation of dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {12-15},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = { Genetic analysis of dairy cattle has been undertaken using an animal  model including pedigree records since 1940 and performance records since  1986. The animal model analyses all breeds and breed crosses  simultaneously allowing accurate estimation of hybrid vigour effects for  milk production, liveweight, four survival traits and 16 linear type traits.  The animal model allows the effects of induction, age at calving and herd-  year-season to be taken into account when estimating an animal},
	issn = {1176-5283},
	author = {Harris BL and Clark JM and Jackson RG}
}
@conference {40616,
	title = {Accounting for scale effects in genetic evaluation of dairy cattle.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {54},
	year = {1994},
	month = {Jan},
	pages = {276-280},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Lactation records of dairy cows calving between 1986 and 1989 were  
obtained from the Livestock Improvement Corporation of the New Zealand  
Dairy Board.  There were milkfat yields from 2,004,854 lactations in 83,805  
contemporary groups.  The data were divided into three equal-sized subsets  
based on average level of production (scale) in the contemporary group; these  
being (kg milkfat {\textpm} sd) High (H), 172 {\textpm} 28; Medium (M), 152 {\textpm} 26; and Low  
(L), 139 {\textpm} 25.  The objectives of this study were to provide evidence of  
heterogenous variance and to identify the best of three methods to stabilise  
the variance of milkfat yields for use in the genetic evaluation of New Zealand  
dairy cattle based on a best linear unbiased prediction procedure using an  
across breeds animal model which will be implemented in July 1996. 
 
The methods investigated for the accounting of scaling were adjustment based  
on: contemporary group standard deviation (SD); contemporary group means  
(MEAN); and logarithmic transformation (LOG) of milkfat yield.  The overall  
correlation between contemporary group means and standard deviations was  
0.44.  This value was reduced to 0.31 in SD-transformed data, -0.27 (MEAN)  
and -0.24 (LOG). 
 
Correlations between breeding values for sires estimated from the independent  
data sets using a mixed model but without adjustment for scale were 0.76, 0.73  
and 0.78 in the L-M, L-H and M-H comparisons.  These were lower than  
expected correlations of 0.85, 0.85 and 0.87, reflecting inaccuracies in sire  
evaluation when scaling is ignored.  Calculated correlations were similar for  
SD and MEAN (0.78, 0.75 and 0.80; 0.78, 0.74 and 0.78), but LOG reduced  
the calculated correlations (0.73, 0.69 and 0.75). 
 
Results confirm the problem of scaling on genetic evaluation of New Zealand  
dairy cattle and indicate other methods need to be studies to correct the  
scaling problem. },
	issn = {1176-5283},
	author = {Lopez-Villalobos N and Garrick DJ and Harris BL and Blair HT}
}
@conference {40463,
	title = {A prototype sire evaluation for New Zealand dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {53},
	year = {1993},
	month = {Jan},
	pages = {91-94},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Growth of mammary epithelium is regulated by endocrine signals, local factors and sensitivity of epithelial cells to mitogens and inhibitors. This study was designed to identify how these factors interact in regulating mammogenesis and determine if breed differences exist among these factors.  Mammary epithelial cell organoids were isolated from five pairs of beef and dairy heifers (7 to 9 months of age) and cultured within collagen gels. Sera were collected from all heifers and pooled within breed for use in culture. At slaughter, explants of mammary fat pad were also prepared for culture.  Culture treatments were arranged in a 2x2x3x4 factorial design. Factors included source of cells (beef or dairy), addition of growth factors (10 ng/ml IGF-I + 50 ng/ml EGF or control), source of mammary fat pad explants (beef, dairy or none) and source of serum added to culture media at 5\% final concentration (beef, dairy, foetal calf serum, or none). Mammary growth was assessed as incorporation of [3H]thymidine into DNA. Mammary epithelial cells from beef heifers grew more rapidly than dairy cells (2518 vs 1192) cpm/ug; P<0.01). Growth of epithelia was enhanced by addition of growth factors (2265 vs 1445 cpm/ug; P<0.01). Sera from both beef and dairy heifers stimulated growth 2-fold compared to no serum (P<0.01), but addition of mammary fat inhibited epithelial growth (P<0.05). Cells from beef heifers were also more responsive to addition of serum and growth factors. These findings demonstrate that multiple factors interact to control mammary growth. Mammary fat pad of ruminants, unlike rodents, appears to inhibit epithelial growth.},
	issn = {1176-5283},
	author = {Garrick DJ and Harris BL and Shannon P and Sosa-Ferreyra C}
}
@conference {40125,
	title = {Optimal cow replacement on New Zealand seasonal supply dairy farms},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {48},
	year = {1988},
	month = {Jan},
	pages = {243-246},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {The use of computer models to predict the ratio of outputs to inputs can be considerable assistance in developing breeding objectives and assessing research priorities and evaluating the impact of changes in management on efficiency of production in the deer industry. Therefore we have developed a model (based on Parks (1982) which quantifies the inputs of feed and the output of carcass to calculate the biological efficiency of the hind/calf unit over the lifetime of the breeding hind. The model has been used to examine the effects of reproductive lifespan (age of culling), calving rate, twinning, changes in sex ratio and changes in calving date on efficiency. In all cases there was a peak in efficiency at 62-64 weeks of age. In terms of reproductive lifespan, the most efficient sustainable system involved slaughtering hinds after only 3 calvings, although the overall impact of this factor on efficiency was small. Changes in calving rate (proportion of hinds calving) had a marked effect with efficiency declining by 5 to 7\% for a 10\% decline in the calving rate. Twinning also had a major effect with about a 3\% change for a 10\% change in twinning rate although the higher pre-weaning mortality of twins compared with singles would markedly reduce real gains. Changes in the sex ratio also altered the efficiency of the system by 3 to 4\% per 10\% unit change in the proportion of males. In contrast, advancing the calving rate by 3 or 6 weeks did not change efficiency or live weight of progeny at the same age but did result in a 2.8\% increase in live weight at the same date for every 3 weeks advancement in calving.},
	issn = {1176-5283},
	author = {Harris BL}
}
