Genetic correlations of milk production and type traits with somatic cell score from Holstein cows in Hokkaido [Japan]
2005
Miura, S.(Obihiro Univ. of Agriculture and Veterinary Medicine, Hokkaido (Japan)) | Suzuki, M.
Genetic correlations between somatic cell score (SCS) and other traits (milk, fat, SNF and protein yields, and type traits) were estimated using test-day records from Hokkaido Dairy Cattle Milk Recording and Testing Association and conformation records from Hokkaido Holstein Agricultural Cooperation. The numbers of records used for estimation of genetic correlation in most type traits were 181291, 104105, and 30973 records on first to third lactation, respectively. The bi-variate statistical model contained additive genetic effects and residual errors as random effects, and they also contained fixed effects for herd-test-day, age of calving, linear regression on days after calving, and Wilmilk's function of days after calving in somatic cell score and herd-classification, age of classification, stage of lactation, and classifier in type traits. Genetic correlations estimated between SCS and milk production traits were low (from -0.22 to 0.15), and were positive in the first lactation and negative in later lactations. Genetic correlations among SCS and conformation traits were also estimated. Signs of the correlations changed across the parities, most likely depending on the growth. Higher negative genetic correlations with SCS were estimated for udder depth (from -0.29 to -0.19) and for fore udder attachment (from -0.25 to -0.07). These conformation traits were associated with the lifetime production and herd life ; thus, genetic improvement of these conformation traits may reduce SCS, further increasing lifetime production.
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