Abstract
Summary: Passive lability of body core temperature during brief exposures to thermal stress is an efficient means of thermoregulation which few species of domestic animals appear to utilize. The body temperature changes of 30 shorn sheep and 10 shorn goats have been measured during standard heat and cold exposures lasting 7 h. During exposures to heat, air temperature was increased from 20 °C to 45 °C then reduced again to 20 °C. Rectal temperatures of goats and Soay, Welsh Mountain, Merino and Clun Forest sheep rose by an average of 1·96 °C, 1·22 °C, 1·04 °C, 0·85 °C and 0·80 °C respectively. All animals had similar increases in respiratory rate. During exposures to cold, air temperature was reduced from 20 °C to about 6 °C then increased again to 20 °C. Rectal temperatures rose by 0·18–0·20 °C in goats and in all sheep except Soays in which they fell by 0·28 °C. All animals showed moderate to vigorous shivering. None of the animals exhibited passive body temperature lability as an adaptation to thermal stress.