The effect of melatonin treatment on reproductive efficiency in an accelerated lambing system

A trial, which involved 917 ewes, was conducted to examine whether reproductive traits could be improved in an accelerated lambing system with 3 lambing seasons per year by subcutaneous melatonin treatment. Fertility (ewes lambed per ewes put to the ram), litter size and the interval between melatonin application date and lambing date were not affected by treatment. However, in the first lambing season (15 February to 15 March), fertility was 16% higher in melatonin-treated ewes compared to untreated ewes (P > 0.05). Season or month of application therefore seems to be an important factor with regard to the response. It is concluded that melatonin treatment in accelerated lambing systems is further complicated by the presence of pregnant and lactating ewes, which makes the value of commercial use thereof doubtful.