Thermal Environment, Sleep and Energy Metabolism in Piglets

Abstract

Heat production, respiratory quotient (RQ) and body temperature were measured in 1- to 9-d old piglets during the individual REM sleep episodes and compared with the respective values obtained in non-rapid-eye-movement (NREM) sleep. Two-hour measurements were carried out in· metabolic respiratory chambers under comfortable ther­ mal conditions and upon exposure to cold. Thermal comfort was provided by heating the flocr to 37°C to 38 °C for 1- to 5-d old piglets and to 34°C to 36 °c for the older animals. The air temperature in the chamber ranged between 25°C and 26 0c. Exposure· to cold was produced by decreasing the floor temperature to 28 cc. Under cold exposure the total duration of REM sleep was reduced by 50 to 60 %. Both. the number of REM sleep episodes. and their duration were decreased. Heat production in REM sleep was invariably reduced. Under exposure to cold this decrease was highly significant (P < 0.01) owing to the disappearance of muscular tremor. However, concurrent decrease in body temperature, recorded in 1- to 3-d old piglets, was not significant. In the thermoneutral environment a significant (P < 0.05) decrease in heat production was observed during REM episodes occurring shortly after food intake. By depressing the postprandial thermogenesis, REM sleep contributes apparently to more effective utilization of the food energy. Lower RQ values observed in REM sleep are related to lower glucose oxidation under muscular atony. Sleep, thermal environment, oxygen consumption, RQ