Abstract:
Proc- Aust. Soc. Anim Prod. (1978) 12: 182 BREED AND CROSSING EFFECTS ON POST-WEANING GROWTH RATE OF STEERS J.H.L. MORGAN*, D.W. McKEOWN* and G.R. SAUL* Post-weaning growth rate is together with initial weight and carcass weight at any given age. parisons need to be substantiated important to the steer fattener because, dressing percentage, it determines The results of overseas breed comfor the pastoral environment of Victoria. . From 1970 to 1973 Hereford (H) and Friesian (F) cows were inseminated to H, F, Charolais (C) and Brahman (B) bulls. Each year's steer progeny were weaned at eight months, grazed on'improved pasture at a moderate stocking rate,without supplementation and slaughtered at two of the following ages : 8, 16, 27 and 42 months. Least squares means of live weights and average daily gains (g day-l) based on unfasted live weights are presented in the table; there were no significant interactions between the effects of the dam and sire breeds. The progeny of H dams grew faster than those of F dams from weaning to 16 months of age, demonstrating an ability to compensate, in part, for their lower weaning weight. Nevertheless the progeny of F dams retained most of their liveweight advantage to 42 months of age. F sired steers grew the fastest from weaning to 16 months of age and tended to maintain some growth advantage to 27 months. Despite the advantage in postweaning gain of F over C sires, their carcases were of similar weight at 27 months (Morgan et a$. 1978) due to differences in weaning weight and dressing percentage. From 27to 42 months of age, H and C sired steers grew the fastest and B sired steers the slowest. However, sire breed differences in carcass weight at 42 months were relatively small and non significant. These results are in general agreement with those of Everitt, Jury and Ward (1975) in demonstrating the high post-weaning growth rate of F sired steers in a temperate pastoral environment. But they also show that differences in post weaning growth rate between these four sire breeds were relatively small in terms of their influence on carcass weight. We suggest, therefore, that for the pastoral conditions of southern Australia, the choice between these breeds should be based on characteristics other than post-weaning growth rate. EVERITT, G.C., JURY, K.E. and WARD, J.D.B. (1975). Proc. N.Z. Soc. .Anim. P&L g: 147. MORGAN, J.H.L., CLARKE, A.J., McKEOWN, D.W. and SAUL, G.R. (1978). Proc, Aust. Soc. Anim. Prod. 12: ----.- - * Pastoral Research Institute, P.O. Box 180, Hamilton, Vic. 3300. 182.