Lamb mortality in Scottish hill flocks

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Abstract
SUMMARY: 1. Records on lamb mortality from birth to marking at approximately 6 weeks are summarised for four seasons in one Cheviot and three Scottish Blackface flocks and discussed in relation to the breed, environmental and management differences existing on the three farms of Sourhope, Roxburghshire; Lephinmore, Argyllshire and Glensaugh, Kincardineshire.2. The mortality rates in single-born lambs from three-year-old and older ewes, following hill lambings, were 12% and 6% respectively in the Cheviot and Blackface flocks at Sourhope and 14% in the Blackface flock at Lephinmore. In the Blackface flock at Glensaugh, the mortality rate following regular pre-lambing feeding and lambing on cultivated pastures was 5%.3. There was considerably heavier mortality in twin-born lambs, and in single-born lambs from two-year-old ewes, notably as a result of increased loss subsequent to birth.4. Among single-born lambs, more males were lost than females, the difference being between 1% and 8% according to the farm and being largely due to a greater frequency of difficult births among males.5. Lambs with birth weights markedly heavier or lighter than average had a higher percentage of mortality.6. An abnormal incidence of loss from difficult birth in a Cheviot sub-flock in 1957 is described.