Assessment of thermoregulatory and postprandial thermogenesis over the first 24 hours after birth in pigs.

Heat production was continuously measured from birth to 24 h after birth in pigs tube-fed 14 g kg-1 of colostrum or water (sham-fed animals) at hourly intervals, and maintained at thermoneutrality (34 degrees C) or in moderate cold (24 degrees C). Results indicate that colostrum was necessary to initiate and sustain the postnatal rise in metabolic rate observed at 34 degrees C. It provided about 75% of the energy required for heat production at 24 degrees C. Heat production was increased by 74% in the cold and decreased by 30% during starvation. In both cases, maintenance of the energy balance was achieved with a compensatory drop in body temperature. At 34 degrees C, variations in postmeal heat production represented 12% of the total 24 h energy expenditure and were almost equally due to the thermogenic effect of colostrum and to confounding factors, including physical activity. In the cold, calculated postmeal thermogenesis accounted only for 3% of 24 h energy expenditure and for 9% of the extra heat produced in the cold. Our results highlight the main role of colostral energy in the energy metabolism of the newborn pig in a typical birth environment (24 degrees C) and in thermoneutral conditions (34 degrees C). Thermoneutral postmeal thermogenesis is low and its contribution to the extra heat produced in the cold very limited.