As a result of increasing on-farm costs, farmers are aiming to increase the number of saleable lambs by lambing yearling ewes. This study investigated lamb survival rates in lambs born to yearlings from birth to three days of age. Data were collected from six recorded flocks in 2007 and 2008, involving 880 yearling ewes giving birth to 557 single and 756 twin lambs. All lambs were weighed at birth and at weaning. Lambs that died within the first three days of life were subject to post-mortem to determine the primary cause of death. Mean lamb survival to three days of age was 80% and survival to weaning was 72%. There were significantly less twin lambs born alive, than single lambs (90%, CI 88% - 92%, cf. 95%, CI 93% - 96%, P <0.05). Twin lambs had a higher death rate due to starvation/exposure, (6.3%, CI 5.3% - 7.4% cf. 2.8%, CI 2% - 3.8%, P <0.05) than single lambs. Dystocia did not differ significantly between single and twin lambs (6% cf. 10% respectively; P >0.05). Mortality in the first few days after birth is higher in yearlings than in flock ewes and higher in twins than singles.
Proceedings of the New Zealand Society of Animal Production, Volume 70, Palmerston North, 96-100, 2010
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