Effects of bodyweight and PMS administration on reproduction rate in Merino ewes

Data are presented on the effects of the use of pregnant mare serum gonadotrophin (PMS) and of increased liverweight on the number of lambs born, or in utero, in mature fine-woolled Merino ewes. The primary effect of increased bodyweight was to reduce the number of barren ewes whereas the main effect of PMS treatment was to increase the level of twinning among those ewes which conceived. The 2 effects appeared to be additive but it is pointed out that the survival rate of the lambs will be an important consideration in assessing the relative merits of the 2 treatments.