Metabolism and insulation of swine as bare-skinned mammals.

Abstract

Metabolism and temperature of the bare skin were compared in 2 young 50-kg boars of the stock called Hamprace raised in Alaska from crosses of Landrace and Hampshire swine. Between 20° and 0°C the average metabolism of the young boars was at the rate of 0.35 ml/O2/gm/hr. The critical temperature for metabolism was about 0°C and, in colder air, metabolism increased about along the line set by the law of cooling. The mean frequency of the heart beat also increased below 0°C. Temperature of the bare skin on the shoulders decreased as the surrounding air cooled along a curve becoming asymptotic in air near 0°C. In cooling to the critical temperature vasoconstriction increased until insulation became maximal at the critical temperature. Below the critical temperature the metabolic increase was often above the line prescribed by the view of stable maximum insulation. Temperature measurements showed that, when superficial tissues became cold, phasic relaxation of peripheral vasoconstriction often reduced the over-all insulation. Apparently concern for circulation in superficial tissues could locally dominate the over-all regulation of insulation. Bare-skinned swine use the heterothermous capability of their peripheral tissues in an over-all insulation of their bodies which is comparable to the physiological insulation of fur-bearing mammals. Submitted on April 9, 1956