|Van Vleck, Lloyd|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 5/30/2000
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: For four generations, half of the university research Holstein herd was bred to Holstein sires with predicted transmitting ability for type (PTAT) > 1.50 and the remainder to sires with PTAT < 1.25, with nearly equal PTA for yield traits for both groups. Data on first lactation cows for 16 linear type traits, final score, and milk, fat, and protein lactation yields were collected from 1986 to 1999 and on somatic cell scores (SCS) from 1992 to 1999. Estimates of heritabilities, genetic correlations, and phenotypic correlations were obtained from REML estimates of (co)variance components. Fixed effects were date cows were classified, age in days at freshening as a linear covariate, and days in lactation at classification as linear and quadratic covariates in model for type and year-season in which a cow freshened in model for yield and SCS. Animal genetic and residual were random effects. Heritability estimates for linear type traits sranged from 0.04 to 0.47. Final score, and milk, fat, and protein yields had heritability estimates of 0.38, 0.13, 0.22 and 0.09, respectively. Heritability estimate of SCS was 0.38. Estimates of genetic correlations among linear type traits ranged from -0.79 to 1.00 and of phenotypic correlations ranged from -0.27 to 0.84. Estimates of genetic correlations of final score with SCS and milk, fat, and protein yields were -0.68, 0.04, -0.16, and 0.10, respectively. Phenotypic correlations of final score with SCS and milk, fat, and protein yields were -0.16, 0.17, 0.10, and 0.22, respectively. The genetic correlation between final score and SCS suggests that selection for increased final score would decrease SCS, whereas, the correlations between final score and yield traits suggests that selection for increased final score would result in little change in yield traits.