GENETIC CORRELATIONS BETWEEN PERFORMANCE OF INDIVIDUALLY FED AND FEEDLOT FED BULLS

The performance of Bonsmara bulls tested in Phase C of the South Afric an Performance Testing Scheme (intensive test in which individual feed intakes are measured) was compared with the performance of the half-s ib bulls tested in Phase D (comparable to commercial feedlot condition s). Birth weight and yearling weight did not differ significantly betw een bulls tested in the two phases. Although bulls entering Phase C we re selected for weaning weight, the ADG (average daily gain) and Kleib er ratios (ADG/yearling weight0.75) of bulls in Phase D were significa ntly higher than those of bulls in Phase C. Preweaning performance sho uld thus not be used to predict postweaning performance. As the geneti c correlations between half-sibs in Phases C and D for yearling weight (1.104 +/- 0.141), ADG (1.008 +/- 0.005) and the Kleiber ratio (0.777 +/- 0.179) were close to unity, it is concluded that the progeny of b ulls performing well in Phase C will perform well under intensive feed lot conditions.