Effect of Accelerated Lambing System with Melatonin Feeding on Reproductive Performance for 2 Years in Suffolk Sheep Raised in Hokkaido.

This study was conducted to determine the effect of accelerated lambing caused by melatonin feeding in the spring on increasing lamb production. Forty-six Suffolk ewes, which conceived last autumn and expected to give birth in February of this year, were divided into 2 groups as follows. Group 1 (treatment, n=23) and Group 2 (control, n=23) ewes were adapted to accelerated lambing and natural lambing, respectively. The accelerated lambing system composed of melatonin feeding for 60-90 days starting in late March followed by ram introduction in May and re-breeding after autumn lambing. The natural lambing system was established so that the ewes were isolated from the rams until autumn resulting in one lambing per year. In these 2 groups, the reproductive performance was evaluated. In the accelerated lambing system, 78% of the ewes (18/23) successfully produced 3 sets of lambs every 2 years. The prolificacy per year of the ewes that were involved in the accelerated lambing system was more than that in the control ewes (224% vs. 159%, p<0.01). The present results demonstrated that the accelerated lambing system with melatonin feeding only once every 2 years could result in greater lamb production than the natural lambing system.