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Correlation Analysis among Milk Yield, Milk Composition, and Somatic Cell Scores by Definition of Contemporary Group  

Jung, Woon-Young (National institute of Animal Science, RDA)
Cho, Kwang-Hyun (National institute of Animal Science, RDA)
Choi, Tae-Jeong (National institute of Animal Science, RDA)
Choi, Jae-Kwan (National institute of Animal Science, RDA)
Choi, Ho-Sung (Department of Animal Biotechnology, Jeonbuk National Univ)
Cho, Ju-Hyun (National Agricaltural Cooperative Federation)
Choy, Yun-Ho (National institute of Animal Science, RDA)
Publication Information
Journal of agriculture & life science / v.46, no.1, 2012 , pp. 113-121 More about this Journal
Abstract
A total of 150,624 records of Holstein milk production collected from 2005 to 2009 were analyzed to investigate the effects of two different contemporary group definitions, parity and somatic cell score (SCS). The first definition (H BY S) of contemporary group was milking cows and heifers born in the same year and season. And the second thing (H CY S) was milking cow and heifers that delivered calves in the same year and season. Effects of contemporary group, parity and regression effect on SCS from two models were highly significant sources of variation. Coverage of variation ($R^2$) was somewhat higher in models with H BY S as contemporary group. From multivariate models with H BY S, phenotypic correlation coefficients of milk components were estimated high and positive. However, the phenotypic correlation coefficient between milk yield and SCS was -0.09, which was low enough to evidence no correlation between them. Phenotypic correlation between SCS and butter fat or between SCS and protein were also negligible but negative. From multivariate models with H CY S as contemporary group, phenotypic correlation among milk traits and SCS were similar to the estimates from models with H BY S. However, SCS in these models were lowly but negatively correlated with milk yield, milk protein, butter fat or SNF, and the phenotypic correlation coefficients of which were -0.10, -0.08, -0.08, -0.11, respectively.
Keywords
Somatic cell score; Milk components; Environmental effect; Contemporary Group;
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