Inheritance of birthcoats in a strain of Merino sheep.

Further observations on the inheritance of birthcoat grade in a flock of South Australian strain of Merino sheep are reported. These observations indicate that the inheritance is multifactorial and that the phenotypic variation is adequately accounted for by an additive genetic situation. The heritability of birthcoat grade was found to be 0.70 ± 0.035 from the regression of offspring on mid-parent and of the order of 0.72-0.78 from full-sib correlations. A difference, highly significant statistically, was observed between the birthcoat grade of ram and ewe lambs. Ewe lambs tended to be 0.35 grade coarser than ram lambs. Examination of published data (Rendel 1954) revealed that a similar difference also occurs between the sexes in the Welsh Mountain breed. A significant deficiency of female progeny was observed among the offspring of fine birthcoat ewes. There is no ready explanation of this loss but it almost certainly results from pre-natal death of a proportion of female embryos carried by fine ewes.