ESTIMATES OF DIRECT AND MATERNAL CORRELATIONS AMONG GROWTH TRAITS IN AUSTRALIAN BEEF-CATTLE

Estimates of covariance components between birth, weaning, yearling and final weight of Australian Angus and Zebu Cross cattle were obtained from a series of bivariate Restricted Maximum Likelihood analyses, fitting an animal model incorporating both genetic and permanent environmental maternal effects. This involved the estimation of up to 16 parameters simultaneously. Problems encountered with this kind of analysis are discussed. On the whole, estimates of variances and heritabilities agreed well with results from previous, univariate analyses. Correlations were considerably more robust against an incorrect model of analysis than heritabilities. Estimates of maternal genetic and environmental correlations among the three later weights were essentially unity. Genetic correlations amongst these traits were very high, 0.9 or more for Angus and 0.7 or higher for Zebu Crosses.