Temperature regulation in the new-born lamb. III. Effect of environmental temperature on metabolic rate body temperatures, and respiratory quotient

Abstract

Studies were made on temperature regulation of lambs in a closed circuit indirect calorimeter. Dry new-born lambs were able to maintain normal body temperature in ambient temperatures as low as -5°C. This was accomplished by increasing heat production to 2–3 times "basal" levels, apparently by increased oxidation of fats, and by reducing heat loss through the extremities by vasoconstriction. The lower limit of the zone of thermal neutrality was about 29°C. In unsuckled lambs within 24 hr of birth, the heat produced in response to cold appeared to be independent of pre-natal nutrition and age. It was considerably lower in lambs with hairy coats than in lambs with fine coats. Milk intake increased heat production, and this increase was abolished after 12 hr of fasting in lambs up to 3 days old, but the increase persisted in older lambs. The increase was accompanied by, and was apparently due to, elevated heat loss from the extremities, which persisted even at low temperatures. The maximal thermal insulation of the tissues, calculated from these results, was about 1 Clo; that of the fleece plus air was only 1 to 2 Clo.