Reproductive performances of creole and black-belly ewes in the West Indies. A new major gene controlling ovulation rate?

Abstract

In a first experiment, fertility and litter size of Creole ewes from Martinique (CM) were analysed in two distinct flocks, one raised on a Pangola irrigated pasture (I), the other on a non-irrigated pasture (NI). Within the two flocks, mating was carried out three times per year in April, August and December, during 5 consecutive years. In flock I fertility was high (84%), but was slightly lower in April, as was litter size in December; in the NI flock the performances were lower and the seasonal effect was increased. In a second experiment, oestrous behaviour and ovulatory activity (monitored by laparoscopy and progesterone determinations) of CM ewes and of another tropical breed, the Black-Belly from Barbados (BM), maintained in the same management scheme and in good body condition, were compared. CM and BB ewes were cycling all year round. Analysis of their ovulation rate suggested the existence of a major gene acting on ovulation rate in CM ewes (additive effect of about 1.0 ovulation).