An association between ram fertility and reproductive performance of Merino ewes of different ages.

Results are presented which suggest that, when ram fertility is non-limiting, there is no difference between ewes of different ages but similar body weights, in the percentage of ewes lambing. However, when ram fertility is depressed, this appears to have a greater effect on the performance of the younger ewes. This result is explained in terms of differences in mating behaviour, it is discussed as a contributor to reproductive wastage and, after more research, as a potential tool in the field diagnosis of ram infertility.