Interaction between the effects of nutrition and season of mating on reproductive performance in crossbred ewes

Abstract

The reproductive performance of first-cross Border Leicester X Merino ewes was measured at two levels of nutrition and at two seasons of mating. The number of dry ewes was greater at a low than at a high level of nutrition, and was greater at a December mating than at a March mating. These effects were independent. The incidence of both twin ovulation and twin births was greater at a high than at a low level of nutrition, and was greater in March than in December. These effects showed significant interaction. Seasonal changes in twinning rates were more pronounced at a high than at a low level of nutrition, and level of nutrition affected twinning rate to a greater extent in March than in December.