Temperature regulation in the new-born lamb. IV. The effect of wind and evaporation of water from the coat on metabolic rate and body temperature

Abstract

The study of temperature regulation in new-born lambs has been extended from dry lambs in "still air" at various ambient temperatures to dry lambs in a wind of 550 cm sec-l, and to lambs whose coats are drying. Exposure to wind resulted in an increased slope of the line relating heat production to ambient temperature, but under the experimental conditions evaporation of water from the coat added approximately the same increment at all ambient temperatures. The effects of wind and evaporation at any one temperature appeared additive. The heat loss from naturally wet new-born lambs less than 1 hr old, in a wind, was greater than in slightly older lambs wetted with tap water. Lambs with hairy coats were able to conserve heat more readily than lambs with fine coats. The cooling efficiency of evaporation from the coat was about 25%. The elevation in temperature of the extremities which follows feeding and persists under conditions of moderate heat loss, appears to be almost abolished under conditions of high heat loss. During the studies on drying lambs, beat loss in many lambs exceeded heat production, and rectal temperature fell, which thus indicated the maximum possible heat production (summit metabolic rate) of which lambs are capable. Lambs from ewes on low or medium levels of feeding during pregnancy cooled more readily than lambs from well-fed ewes.