Responses of ewes to melatonin implants: importance of the interval between treatment and ram introduction on the synchrony of mating, and effects on ovulation rate

Abstract

AbstractAn experiment was conducted to investigate the effects of the length of the interval between implantation with melatonin and ram introduction on mating patterns, and to investigate the effects of melatonin on ovulation rate and litter size in Mule ewes.Increasing the interval from treatment to ram introduction from 4 to 6 weeks was associated with a progressive and significant reduction in the time from ram introduction to mating as well as a reduction in the spread of mating across the group.Melatonin resulted in a significant and consistent increase in ovulation rate at first oestrus (+0·44 to +0·48 ovulations per ewe) across the three treated groups, although the increase in litter size (+0·19 to +0·36) was more variable.It is concluded that melatonin influences the pattern of mating and increases litter size in ewes and that the increase in litter size is accounted for by an induced increase in ovulation rate.