Variance component and heritability estimates for growth traits in the Nguni cattle stud at Bartlow Combine

Data collected from calves bom 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. Data van kalwers wat op die Bartlow Combine Teelstasie gebore is, is ontleed om direkte en maternale additiewe genetiese variansies en gevolglike oorerflikhede van gewig op geboorte,205-,365- en 540-dae ouderdom, te bepaal. Die beraming van direkte oorerflikheid was 0.41,0.29,0.26 en 0.19; maternale oorerflikheid 0.16,0.20,0.08 en 0.003 en totale oorerflikheid 0.44,0.40,0.34 en 0.21, onderskeidelik. Die korrelasie tussen die direkte en maternale komponente was -0.49, -0.39, -0.08 en 0.97. Dit word voorgestel dat beide direkte en maternale teeltwaardes in'n seleksieprogram vir geboorte en 205-dae gewig ingesluit word. Weens die klassifikasie as'n moederlyn is die verbetering van die maternale komponent van spesifieke belang by die Nguni. Die resultate vir 365- en ,540-dae gewig dui daarop dat die maternale komponent van minder belang is en dat seleksie gebaseer op direkte teeltwaarde, gewig op hierdie ouderdomme suksesvol kan verander.