Lambing  performance for 878 Hyfer ewes joined three times in February, October and June in an 8-monthly lambing system is reported. The ewes were unselected progeny from a Control flock and a flock selected for weight of lamb weaned per ewe joined. The Select flock ewes were 9% higher than the Control flock ewes for weight of lamb weaned (P<0.05), with the component traits lamb survival and lamb growth contributing most of the difference. There were significant effects of season on fertility, litter size (P<0.05) and lamb survival (P<0.01). Joinings in June resulted in the lowest fertility and litter size, whereas lamb survival was lowest from the February joining. Estimates of heritability for litter size and lambs bom were 0.15+0.06 and 0.08+0.04 respectively with little additive variation for the other traits. Between season repeatability ranged from 0.12 to 0.17 for all traits except lamb survival which was zero. Keywords: reproduction, breeding season, heritability, repeatability, Hyfe

N. M Fogarty, A. R Gilmour

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 27: Reproduction; fish breeding; genetics and the environment; genetics in agricultural systems; disease resistance; animal welf, , 55–58, 1998
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