Implanting Melatonin at Lambing Enhances Lamb Growth and Maintains High Fat Content in Milk

Abstract

Background: Recent studies have shown that melatonin implants administered during pregnancy reduced neonatal lamb mortality and produced high survival rates at weaning. This study was designed to quantify the effects of melatonin implantation of ewes and lambs immediately after lambing on the growth of lambs and the quality of milk throughout lactation.Results: In experiment 1, treatment with melatonin the lambs did not have a significant effect on liveweight (LW) (±S.E.M.) at weaning or average daily gain (ADG) until weaning. These results were similar in experiment 2, although lambs reared by melatonin-implanted ewes presented significantly (P<0.05) higher LW at weaning and ADG than did lambs from control ewes. The effect of melatonin implantation of the mothers was particularly evident in male lambs, so that male lambs reared by treated ewes presented significantly higher LW at week 2, 3, and 4 than did male lambs reared by control ewes. The fat content of milk was significantly (P<0.05) higher in implanted ewes than it was in control ewes at day 45 of lactation. Protein and lactose content of milk did not differ significantly between groups. In experiment 3, using artificially-reared lambs, melatonin treatment of the lambs at birth did not have a significant effect on LW at weaning, or ADG. Conclusions: Melatonin treatment of ewes at lambing induced a high growth rate of their lambs and increased the fat content of the milk; however, the direct treatment with melatonin of the lambs at birth did not have an effect in their growth rate.