Development of a model for estimation of breeding values for beef cattle in Germany .2. Estimation of genetic parameters

Estimation of genetic parameters for birth weight, weaning weight, and yearling weight was based on field data from Charolais and German Angus. Maternal permanent environmental effects as well as maternal genetic effects allowing for covariance between direct and maternal effects were taken into account. Considering maternal genetic effects for Charolais decreased residual variances and increased log-likelihoods significantly for all traits, The genetic correlation between direct and maternal genetic effects was consistently negative for all traits (r(am) = -(.)49 to -(.)54 for Charolais). However, estimated heritabilities showed high values, especially for German Angus. The maternal genetic effect of:Charolais was highest for weaning weight (m(2) = 0.21). Maternal heritabilities for birth and yearling weight were 0.16 and 0.13, respectively. Fitting a maternal permanent environmental effects led to robust estimation of genetic variances, independent of the data structure. Therefore, this model seems to be appropriate for the estimation of breeding values based on the present structure of beef cattle breeding. For Charolais the estimates of the maternal permanent effects ranged from c(2) = 0.07 (yearling weight) to c(2) = 0.12 (weaning weight). Direct heritability estimates for birth, weaning, and yearling weight of Charolais were 0.28, 0.21, and 0.26, respectively Corresponding heritabilities for German Angus were 0.24, 0.31, and 0.30, respectively. Genetic correlations between all traits were positive. Especially, estimated genetic correlation between weaning weight and yearling weight was high (Charolais: r(g) = 0.92; German Angus: r(g) = 0.97). For a practical estimation of breeding values a multitrait animal model fitting the maternal component as maternal permanent environmental effect may presently be recommended. In future, models should be developed which incorporate a maternal genetic effect.