Some benefits and costs of genetic improvement in New Zealand's sheep and beef cattle industry

摘要

Abstract Breeding objectives for sheep or beef cattle are those which contribute most to increasing a farm's net income. The biological characteristics whose variation contributes most are described, and changes attainable by genetic selection for single characters are calculated. In terms of gain per generation, responses were computed as 0.07 lambs weaned per ewe joined, or 0.85 kg weaning weight, or 0.19 kg greasy fleece weight; in beef cattle, 9.7 kg carcass or 0.032 calves weaned per cow joined. Returns are estimated for single character selection flocks/herds, net of anticipated cost rises associated with higher output, and then calculated again for combined selection. At the same intensity of selection, smaller responses in each character are expected if combined selection is practised, although the rise in net income is expected to be larger with combined selection. In a 200-ewe flock, single character responses and index selection were expected to achieve annual improvements of 0.024 (0.024, inde...