Direct genetic and maternal genetic influences on first lactation production in four breeds of dairy goats

摘要

First lactation records from 1985 to 1995 on 2204 goats of the Alpine, Toggenburg, Saanen and Nubian breeds distributed in 485 herd-years were used to study maternal effects on production. Derivative free restricted maximum likelihood methods were used to fit a model that included breed, herd-year, age at first kidding and site- and dam-phantom groups as fixed effects, and animal direct genetic and maternal genetic effects and residual as random effects. The relationship matrix included relationships among individuals due to direct and maternal genetic effects and due to the covariance between direct and maternal effects. The heritability estimates for direct genetic effects for milk yield were 0.19 +/- 0.06 (without maternal effects in the model) and 0.13 +/- 0.08 (with maternal effects in the model) the corresponding values were 0.21 +/- 0.06 and 0.11 +/- 0.07 for fat yield, and 0.17 +/- 0.06 and 0.07 +/- 0.07, for protein yield. The heritability estimate for maternal effects was 0.05 +/- 0.04 for milk yield, 0.10 +/- 0.04 for fat yield and 0.09 +/- 0.04 for protein yield. The covariance between direct and maternal effects accounted for a small and statistically non-significant proportion of the phenotypic variance for all traits