Proceedings of the New Zealand Society of Animal Production. 1971, 31: 151-163
Proceedings of the New Zealand Society of Animal Production. 1971, 31: 151-163
The first experiment compared, over six years progeny of 62 bulls selected for either fast or slow post-weaning gain in breeders' herds. Differences in progeny gains after weaning were small, reflecting a realized heritability of 0.16.
Six years data were analyzed from a subsequent closed herd selection experiment and associated progeny test herd. Correlations among growth traits, both for individuals (within sires) and for progeny means, were high for liveweights themselves but lower for gains or between weights and gains. For 29 sires progeny-tested in two herds, the repeatability of tests was 0.36 for weaning and 0.43 for yearling weight. The regressions of progeny performance on sire's own performance, based on a total of 55 sires, are presented for different growth traits. Derived heritability estimates were of the order of 0.25 and 0.40 for weaning and yearling weight, but were small and non-significant for post-weaning gain.
The results are compared with overseas findings and discussed in relation to improvement of beef cattle growth performance. It is concluded that worthwhile genetic gains will be achieved by sire selection on yearling or weaning weight but not on weaning to yearling weight gain,
Keywords: NZSAPAB;
