The Influence of Photoperiod and Melatonin on Reproductive Performance of Anestrous Ewes

The effect of altered photoperiod of melatonin, either fed or implanted, on reproductive performance of ewes was evaluated during the 1985 and 1986 breeding seasons. Altered photoperiod (8 hr light : 16 hr dark) resulted in an increased number of breeding marks recorded and a higher lambing rate. However, lambing date was earlier than controls only in trial 2. In trial 2, 91% of the melatonin-implanted ewes lambed compared to 74% of the controls, while, in trail 1, 94% of the ewes receiving melatonin in the feed lambed vs 66% of the controls. Melatonin in either the implanted or fed form appeared ro have little effect on lambing date or number of lambs born in this study