Influence of breed, birth weight and weather on the body temperature of newborn lambs

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Abstract
SUMMARY: The rectal temperature of 208 lambs of Scottish Blackface, Tasmanian Merino, Southdown, Cheviot, Soay and Finnish Landrace breeds was measured between 15 and 25 min after birth, and that of 94 lambs again 1 hr after birth. Relationships within breeds between rectal temperature and birth weight, weather (temperature and wind speed) and gestational age were examined.Within the range of birth weights and weather encountered over a period of years Scottish Blackface, Cheviot and Soay breeds maintained homeothermy at birth. In contrast, the Merino and Finnish Landrace breeds, which had comparable birth weights to the Black-face and Soay respectively, showed significant reductions in body temperature sometimes exceeding 10°C in cold weather. The Southdowns also showed hypothermia. In the Merinos and Finns, 30 and 54% respectively of the variation in rectal temperature was accounted for by birth weight and weather.Of those lambs with low rectal temperatures 20 min after birth, few showed any improvement after 1 hr. Merinos in cold weather showed the least tendency to recover.Possible reasons for the different performance of the breeds and the implications for lamb survival are discussed.