Abstract

A flock of 350 to 400 Dorset x Romney ewes was split into autumn- and spring-lambing groups in each of 2 years, 1985-86 and 1986- 87. Joining for autumn-lambing commenced at the end of October, with most mating occurring in late November to early December. Mean lambing date in autumn was 20 April in 1986 and 24 April in 1987. Spring- lambing ewes were joined with rams on 11 March 1986 and 1 April 1987. Mean lambing data in spring was 20 August in 1986 and 6 September in 1987. Liveweight loss over lactation in autumn-lambing ewes was greater than in spring-lambing ewes. Liveweight gain prior to joining was rapid for autumn-lambing ewes, enabling them to reach a live weight of >50 kg prior to joining to lamb in autumn the following year. Number of lambs born per ewe lambing was 110% and 118% in autumn, and 146% and 120% in spring for 1986 and 1987 respectively. Survival of autumn-born lambs to weaning was 7 to 9% higher than for spring-born lambs. Lamb growth rates were lower between birth and weaning in autumn- than in spring-born lambs. Autumn-lambing ewes produced up to 0.1 kg more wool than those lambing in spring.

GM, Bowen

Proceedings of the New Zealand Society of Animal Production, Volume 48, , 65-68, 1988