EFFECT OF DIETARY-COMPOSITION AND COLD-EXPOSURE ON NON-SHIVERING THERMOGENESIS IN YOUNG-PIGS AND ITS ALTERATION BY THE BETA-BLOCKER PROPRANOLOL

Young pigs were fed on 3 diets consecutively, each diet being given for 1 wk. The diets were given in random order as (g pig feed/kg body wt): 20, 60, 20 plus a supplement with the energy equivalent of 40 g pig feed/kg. The supplements included desiccated coconut, fish meal and glucose. At the end of each week resting metabolic rate, beginning 12-14 h after feeding, was measured overnight using an open-circuit respiration chamber at thermoneutrality. The O2 consumption of pigs on the 60 g/kg diet was always higher than on the 20 g/kg diet. The addition of desiccated coconut or fish meal also increased metabolic rate; with added glucose, O2 consumption tended to be even lower than on 20 g/kg alone. The administration of the .beta.-blocker propranolol to pigs on ad lib food intake reduced the rate of overnight resting O2 consumption, measured from 10 until 20 h after feeding, by 12%, but it had no effect on O2 consumption when the intake was 20 g feed/kg. Exposure to mild cold (15.degree.) caused an increase in O2 consumption and this was reduced by 14% after injection of propranolol.