Sire x ecological region interaction in Bonsmara cattle

The possible interaction between sire and four ecological regions in which Bosmara cattle are mainly found in South Africa was investigated. Birth and weaning weight records of 43 628 registered Bonsmara calves born between 1 976 and 1997 from 18 herds were available. Restricted Maximum Likelihood (R EML) procedures were used in the analyses. Genetic correlations and expecte d correlated response to selection were estimated assuming the same trait ( e.g. weaning weight) to be a different trait when measured in each of four different regions. The results indicate that for the purpose of genetic eva luation, the three bushveld regions need not be separated, but that it woul d be advisable to consider the highveld region as a separate environment. S election of bulls bred on the Highveld for the purpose of genetic improveme nt in the bushveld regions is likely to be less effective than selection of bulls bred anywhere in the bushveld and conversely. The results have also, once again, confirmed that the interaction between sire and contemporary g roup (HYS) is usually more important than between sire and any designated r egion.