Gestation length in Danish Holsteins has weak genetic associations with stillbirth, calving difficulty, and calf size

The objective of this study was to make inference about direct and maternal heritabilities of gestation length (GL), stillbirth (SB), calving difficulty (CD), and calf size (CS) at first calving and to examine whether non-linear genetic associations between these traits exists. Field records from 184 000 Holstein cows calving from 198 8 to 2002 were analysed. Bayesian methodology with Gibbs sampling was used to fit a univariate linear model for GL and a univariate threshold model for the other traits. Bivariate linear models were used to estimate genetic correlations between all traits with a restricted maximum likelihood procedure. The marginal posterior mean of the direct heritability was 0.42 for GL, 0.11 for CD, 0.22 for CS, and 0.10 for SB. The marginal posterior mean of the maternal heritability was 0.07 for GL, 0.07 for CD, 0.04 for CS, and 0.13 for SB. Linear and quadratic regressions of expected breeding values indicated genetic associations between many of the traits, but no indication of non-linear genetic associations was found. Direct effects of GL were estimated to be weakly correlated with direct effects of SB (0.18) and CD (0.38). (C) 2004 Elsevier B.V. All rights reserved.