Effect of early v. late lambing dates on ewe performance, lamb growth, and carcass composition in Canterbury

Abstract

In a trial in Canterbury, two groups of Dorset ewes mated with Corriedale rams had mean lambing dates of 25 July (E) and 26 September (L). Half of the lambs in each group were bom and reared as singles and half as twins. They were weaned at 12 weeks of age. Lambs were slaughtered for measurement of carcass composition at 12, 18, and 24 weeks of age. Ewes in the L group were on average 4.5 kg heavier than those in the E group during lactation, though milk production for both groups was similar (162 litres). Growth rate of lambs between birth and weaning was greater in the L (302 g/day) than E group (263 g/day) and the difference in liveweight of 4.6 kg between groups at weaning was 1 kg greater at 24 weeks of age. There was no difference in carcass composition of lambs between groups. It was concluded that in an average season a later lambing date was advantageous to both ewes and lambs on non-irrigated pasture in Canterbury.

Keywords:

• sheep
• lambing dates
• ewes
• milk production
• lambs
• liveweight gain
• carcass composition