Effects of nutrition, liveweight, and season on the incidence of twin ovulation in South Australian strong-wool Merino ewes

Abstract

The effects of nutrition on the incidence of twin ovulation in strong-wool Merino ewes were studied at two seasons. Liveweight at the time of ovulation was the important determinant of twinning rate. Over the liveweight range 42-57 kg, the incidence of twin ovulation increased by about 2 . 5 % for each 1 kg increase in liveweight at ovulation due to variation in recent nutrition, and by about 1.3 % for each 1 kg of liveweight at ovulation due to inherent variation in liveweight. These relationships did not vary significantly between January and April. The incidence of twin ovulation was not enhanced by a state of increasing liveweight before ovulation ('flushing'), and did not vary significantly between January and April.