EFFECT OF TIME OF CALVING AND SIRE TYPES ON GROWTH OF PROGENY TO WEANING

摘要

Between 232 and 283 cows in each or autumn (March-April) or winter (June-July) calving treatments were artificially inseminated by sires with high estimated breeding values (EBVs) for either retail beef yield (RBY) or intramuscular fat (IMF) in each of two years in the south-west of Western Australia. Calves were raised to weaning in January the following year at approximately 9 and 6 months of age for the autumn and winter calves respectively. Calves by high RBY sires had higher (P<0.001) weaning weight (319.2 vs 308.8 kg) and liveweight gain per day (1.15 vs 1.11 kg) and lower ultrasonically scanned P8 fat thickness (4.44 vs 5.47 mm) than calves by IMF sires had Autumn calves were heavier and fatter (P<0.001) at weaning than winter calves but winter calves grew at a faster rate to weaning (PO.001) than autumn calves.