Environmental temperature, energy metabolism and heat regulation in sheep. II. The partition of heat losses in closely clipped sheep

Abstract

1. The heat emission of two closely clipped sheep was studied in forty experiments in which three feeding levels were employed and in which environmental temperatures ranged from 8 to 38° C.2. The sheep shivered at temperatures below 23° C., but the first reaction to cold was a corrugation of the skin referable to contraction of the fascial muscles.3. As environmental temperature increased voluntary water consumption and urinary volume increased markedly. Only a small degree of cooling resulted from this warming of large quantities of water through a relatively small temperature gradient.4. The basal loss of heat by vaporization of water was 316 Cal./m.2/24 hr. in one sheep (3) and 307 Cal./ m.2/24 hr. in the other (23). Increased vaporization occurred at environmental temperatures of 31° C. for the experiments at the low-feeding level, 27° C. at the medium level and 26° C. at the high level. The water-vapour loss increased subsequently by 87 Cal./m.2/24 hr./° C. change in environmental temperature in sheep 3 and by 88 Cal./m.2/24 hr./° C. in sheep 23. Respiratory frequencies increased with increasing heat loss by vaporization. Some evidence suggests that when the water-vapour loss was high the excretion of potassium through the skin was increased.