Heritability of litter size components were measured on 445 to 528 Romanov ewes, born from 46 sires, and controlled during the first years of reproduction : 1st mating at 9 months of age in November ; 2nd mating at 19 months of age in August-September. The inter-year repeatabilities of ovulation rate (OR), Litter Size (LS), number born alive (NBA) and embryo mortality rate (EM%) are 0.30, 0.12, 0.07 and 0.04 respectively. Heritability of 0R1, 0R2, LSI, LS2, NBA1, NBA2, EM%1 and EM%2 are 0.39, 0.20, 0.02,0.23, 0, 0.28, 0.09 and 0. Heritability of embryo mortality rate at 9 months, during the sexual season, is therefore weak, but not negligible. This demonstrate an interest in taking into account both OR and EM% when selecting on litter size.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume XI. Genetics of reproduction, lactation, growth, adaptation, disease, and parasite resistance., , 90–95, 1986
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