EVALUATION OF BOS-INDICUS AND BOS-TAURUS STRAIGHTBREDS AND CROSSES .2. POST-WEANING GROWTH, PUBERTY, AND PELVIC SIZE OF HEIFERS

Post-weaning growth and body condition, puberty and pelvic size of 197 heifers comprizing straightbred Hereford (HxH) and Brahman (BxB), fir st-cross (BxH) and back-cross (HxBH and BxBH) heifers were evaluated. The heifers were born over a 3 year period, and grazed improved and se mi-improved pastures following weaning at Grafton, New South Wales. Pr ior to weaning, heifers had been reared by dams on three pasture syste ms (high, medium and low quality pastures). Heifers from low quality p re-weaning pasture had higher (P < 0.05) post-weaning liveweight gain than those from high and medium quality pastures. BxH heifers gained 7 1 g/day more (P < 0.05) than the mean gain of their contemporaries of the other genotypes, whose gains were similar, from weaning to either 26 or to 30 months of age. Liveweight at all ages was influenced by ge notype x pre-weaning pasture system interaction. At 30 months of age, BxH heifers from high and medium pre-weaning pastures were the heavies t. At the same age, but from low quality pre-weaning pasture, heifers with crossbred dams (HxBH and BxBH) were the heaviest. Wither height d epended significantly (P < 0.05) on the proportion of Bos indicus gene s, increasing from 113.8 cm in the HxH heifers to 124.4 cm in the BxB heifers at 30 months of age. BxH heifers had a higher (P < 0.05) body condition score than their contemporaries of the other genotypes, whic h were in similar condition, at 26 and 30 months of age. On average (a cross pre-weaning pasture system), 9% of BxB heifers had reached puber ty by 22 months of age compared to 62, 95, 82 and 64% (s.e.=9) for HxH , HxBH, BxH and BxBH heifers respectively. No significant genotype dif ferences were obtained in the height, width and size of the pelvic ope ning of the heifers, measured just prior to the beginning of the matin g season at 26 months of age.