VARIANCE COMPONENT AND HERITABILITY ESTIMATES FOR GROWTH TRAITS IN THE NGUNI CATTLE STUD AT BARTLOW COMBINE

Data collected from calves born at the Bartlow Combine Breeding Station were analysed to estimate direct and maternal additive genetic variances and resulting heritabilities for weight at birth, 205, 365 and 540-days of age. The estimates of direct heritability were 0.41, 0.29, 0.26 and 0.19; maternal heritability 0.16, 0.20, 0.08 and 0.003 and total heritability 0.44, 0.40, 0.34 and 0.21, respectively. The correlations between the direct and maternal components were -0.49, -0.39, -0.08 and 0.97. It is suggested that both direct and maternal breeding values be included in a selection programme for birth and 205-day weight. Because the Nguni is classified as a dam line, the improvement in the maternal component is of particular interest. The results for 365 and 540-day weights indicate that the maternal component is less important and that selection for direct additive values may well be successful in eliciting a response.