Proceedings of the New Zealand Society of Animal Production.
1992, 52: 145-148
Proceedings of the New Zealand Society of Animal Production.
1992, 52: 145-148
Our analyses show that, for the same winter feed requirement, the selected herd when compared with the control herd would have: 88 vs 100 cows wintered; 65 vs 72 calves weaned, and mean calf weaning weight would be 174 vs 158 kg per head. Efficiency was estimated to be 99.8 vs 100 units. Theses results indicate that while selection for yearling weight has resulted in heavier calves and breeding cows, the calculated extra winter feed costs associated with the heavier selected herd makes them no more efficient than the randomly bred control herd. For the selected herd to be more efficient, either a reproductive advantage well in excess of the 3 percent point advantage achieved would be required, or the metabolic efficiency of the selected cows would need to increase. In economic terms, the selected herd may be more efficient than the control herd for 2 reasons. Firstly, since herd size is lower, total herd costs are likely to be lower. Secondly, if a premium exists for heavier calves, the calves from the selected herd are likely to be worth more per head.
Keywords: NZSAPAB; Breeding cows; selection lines; feed requirements; weaning weight; Angus cattle.
