Previous studies have reported up to double the expected rate of response to selection in breeding schemes based on embryo transfer, compared to conventional schemes. However, these studies ignored variation in family size and reduction in genetic variance in selected populations. Using Monte-Carlo simulation for these factors, schemes based on embryo transfer (ET) were found to give responses up to 138 per cent greater than conventional schemes using the same number of sires and generating the same number of calves to go on performance test. A more realistic comparison of a conventional versus an ET scheme is one at the same level of inbreeding generating the same number of calves on test, in this case the ET scheme gave a 53 per cent advantage over the conventional scheme. Previous studies are likely to have overestimated absolute response by up to 50 per cent and to have underestimated rates of inbreeding by 150-250 per cent. In addition, assumption of constant family may have overestimated response by 0-11 per cent and underestimated rates of inbreeding by 11 -48 per cent.

N. R Wray, G. Simm

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume XV. Beef cattle, sheep and pig genetics and breeding, fibre, fur and meat quality., , 315–318, 1990
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