Estimates of Covariance Components for Growth Traits of Australian Charolais Cattle

Restricted maximum likelihood estimates of covariance components and the resulting genetic parameters were obtained for birth, weaning, yearling and final weights and postweaning gain of Australian Charolais cattle fitting an animal model including genetic or permanent environmental maternal effects. No 'carry-over' of maternal effects till weaning on postweaning weights w& found. Direct heritability estimates were 34, 41 and 22% for yearling weight, final weight and postweaning gain respectively. Maternal genetic effects were not important for birth weight and were small for weaning weight. Permanent environmental maternal effects affected birth weight to a moderate extent, but were the main factor determining weaning weight, explaining 4% and 21% of the respective phenotypic variance while direct heritabilities were 21% (birth) and 12% (weaning). Direct genetic correlations between birth and the other weights were medium, ranging from 0.44 to 0.67, while estimates between weaning, yearling and final weight were close to unity.