EFFECTS OF DIETARY ENERGY PLANES ON GROWTH AND HERITABILITY ESTIMATES FOR POSTWEANING GROWTH TRAITS IN YOUNG BEEF BULLS

Records of young AN and young HE bulls were analyzed to evaluate the influences of dietary energy planes on growth and heritability estimates of growth traits during 168-d postweaning test. Estimates of h(a)(2) for end of test weight (WT168), average daily gain on test (ADG 0-168) and relative growth rate on test (RGR 0-168) were much higher in the MED line than in the HED line. Between lines, maternal heritability estimates (h(m)(2)) for WTO and ADG 0-168 were similar. Estimates of h(m)(2) for WT168 was much higher in the HED line than in the MED line. All direct-maternal genetic correlations (r(am)) were negative. These results may indicate that the antagonism between direct and maternal genetic effects for postweaning growth traits in the MED line was much less than that in the HED line.