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 Statio n were analysed to estimate direct and maternal additive genetic varia nces and resulting heritabilities for weight at birth, 205, 365 and 54 0-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 tot al heritability 0.44, 0.40, 0.34 and 0.21, respectively. The correlati ons between the direct and maternal components were -0.49, -0.39, -0.0 8 and 0.97. It is suggested that both direct and maternal breeding val ues 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 importan t and that selection for direct additive values may well be successful in eliciting a response.