The significance of the extremities of the ox (Bos taurus) in thermoregulation

Abstract

1. Measurements of the temperatures of the extremities, rectal temperatures, respiratory rates and heart rates have been made in calves during exposure at environmental temperatures within the range – 5·0° –45·0° C.2. Large variations in the skin temperatures of the extremities were recorded between environmental temperatures of –5·0° and 25·0° C. At environmental temperatures above 25·0° C. the extremity temperatures and the skin temperatures of the trunk were similar.3. Feeding and localized infra-red irradiation of part of the trunk of the animals resulted in marked increases in the skin temperatures of the unheated extremities.4. Evidence was obtained that the variations in the skin temperatures of the extremities were brought about by changes of blood flow to these parts.5. Respiratory rates varied also with the environmental temperature at which the animals were exposed. When the animals were exposed to localized infra-red irradiation of the trunk the increase in respiratory rate was significantly greater when the extremities were initially warm than when they were cool.6. In addition to spontaneous fluctuations in the skin temperatures of the ears at environmental temperatures of 10·0°–25·0° C, periodic increases in the skin temperatures of the ears were observed in all the calves at an environmental temperature of – 5·0° C. The increase in the skin temperatures of the ears persisted throughout the 7 hr. exposure to an environmental temperature of – 5·0° C.7. It was concluded that, in a temperate climate, variations in the skin temperatures of the extremities of the ox have a thermoregulatory function.