The reproductive performance of ewes mated on lucerne

Trials were conducted to make a comparison between the reproductive performances of ewes de‐pastured during mating on lucerne, on the one hand, and on rye‐grass‐white clover, on the other. In general, the lucerne was grown on thinner soils than was the pasture. These trials showed that, under the soil and climatic conditions operating, reproduction was depressed by lucerne relative to grass to the extent of: a retardation in rate of conception of the order of 10%‐15% fewer ewes settling during the first 17 days of mating and a 4‐5 day retardation of mean lambing date; a decrease in the number of twins born of the order of 10%, and an increase in barrenness of 1 %‐2%, giving an overall reduction in lambing percentage of 10%‐12%. Although the factor in the lucerne responsible for these effects was not identified, it is presumed to be the presence of one or more oestrogens; a deficiency of selenium is suggested as another possible causative factor.