@conference {41744,
	title = {Effect of increased somatic cell count on lactation yields of milk , fat and protein},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {67},
	year = {2007},
	month = {Jan},
	pages = {293-296},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Wanaka},
	abstract = {The purpose of this study was to estimate the effect of increased SCC on production in New Zealand dairy farms. Herd test data from lactations one through six were used in the study. Herd test milk, fat and protein yields were modelled as a function of days in milk at the time of the herd test and the logarithm (base 2) of SCC. The model estimates were used to obtain the predicted value for each observation using the actual log SCC and again where the log SCC was increased by one (i.e. doubling the SCC level). For first-lactation cows, the reduction in a 270-day lactation yield from a doubling of the SCC was estimated to be 78 litres, 2.39 kilograms and 2.04 kilograms for milk, fat and protein yield, respectively. Herd SCC level also influenced the extent to which a doubling of SCC decreased production. For first-lactation cows every doubling of SCC was predicted to result in an average loss of 67 and 90 litres in the lowest and highest quartiles, respectively.},
	issn = {1176-5283},
	author = {Winkelman AM and Montgomerie WA and Johnson DL}
}
@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 {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 {41227,
	title = {Genetics of milk characteristics in New Zealand dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {60},
	year = {2000},
	month = {Jan},
	pages = {318-319},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {Data collection was integrated with LIC{\textquoteright}s herd testing service using a sample of 102 herds involved in LIC{\textquoteright}s SireProving Scheme (SPS) in 1995. In addition to milk volumefrom herd testing, the concentrations of fat, crude protein(total nitrogen), casein, whey and lactose were determined.The data was collected from over 3,000 cows born in 1996and first calving in the 1998 spring season, these beingpredominantly the daughters of approximately 220 SPSbulls. The milk characteristics were measured at three herdtests on each cow, with each herd having a herd test in eachof the Sept/Oct, Nov/Dec and Jan/Feb periods. Hereafter,we refer to these three periods as stages of lactation.},
	issn = {1176-5283},
	author = {Johnson DL and Petch SF and Winkelman AM and Bryant M}
}
@conference {40766,
	title = {Associations between milk protein genetic variants and production traits in New Zealand dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {24-27},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Records on 7574 first lactation cows were used to investigate the  associations between milk protein genetic variants and 305-day milk, fat,  and protein yields. Friesians, Jerseys and Ayrshires and their crosses were  represented in the data. Milk samples were typed for 3 casein (CN) proteins  as1-CN (B,C), b-CN (A1, A2), k-CN (A,B) and 1 whey protein b- lactoglobulin (LG) (A,B). The model used to describe the data included the  additive genetic effect of animal and the four protein phenotypes. The interaction between breed and as1-CN phenotype and between breed  and b-CN phenotype was significant (P<0.05) for milk, fat and protein  yields while the interaction between breed and k-CN phenotype was  significant (P<0.05) only for protein yield. The interactions associated with  the as1-CN and k-CN phenotypes were scale effects while the interactions  associated with b-CN resulted from reranking of protein phenotype across  the breeds. Friesian and Jersey as1-CN BB cows had higher (2.8\% and  0.8\%, respectively) milk production and lower (0.3\% and 1.2\%,  respectively) protein production than BC animals while the differences  between the phenotypes for fat production were small. The b-CN A2 allele  was associated with increased production in the Friesians with A2A2 cows  producing approximately 2\% more milk, fat and protein than A1A1 cows.  The opposite effect was found in Jerseys where A2A2 cows produced 3-4\%  less milk, fat, and protein than A1A1 cows. The B allele of k-CN was  associated with a 0.6 to 3.5\% increase in production. The b-LG BB  phenotypes produced approximately 1.3\% less milk and protein and 1.2\%  more fat than the AA phenotypes. The dominance effect was not significant  (P<0.05) for any of the protein phenotypes. },
	issn = {1176-5283},
	author = {Winkelman AM and Wickham BW}
}
