THERMOREGULATION IN NEWBORN LAMBS - INFLUENCE OF FEEDING AND AMBIENT-TEMPERATURE ON BROWN ADIPOSE-TISSUE

We have previously shown that feeding 50 mi of colostrum can increase the thermogenic activity of brown adipose tissue (BAT) in newborn lamb s maintained at a warm (30 degrees C) ambient temperature. This study further examines the effect of ambient temperature on BAT and thermore gulation by investigating the response to feeding 50 mi of water. Imme diately after vaginal birth, lambs were placed in either a warm (30 de grees C) or cool (15 degrees C) environment at ambient temperature and measurements of colonic temperature and heat production were recorded for 6 h. Lambs were fed 50 mi of water when 5 h old. The level of gua nosine 5'-diphosphate (GDP) binding was higher, but adrenaline content lower in BAT sampled From lambs maintained at 15 degrees C compared w ith those at 30 degrees C. Feeding was associated with an increase in colonic temperature and plasma concentrations of glucose and non-ester ified fatty acids in lambs maintained at 15 degrees C only. In this gr oup plasma concentrations of adrenaline and dopamine declined after fe eding, but noradrenaline concentrations were not influenced by feeding in either group of lambs. O-2 consumption and CO2 production were hig her in lambs maintained at 15 degrees C but were not influenced by amb ient temperature or feeding. It is concluded that feeding a small volu me of water can influence thermoregulation by a mechanism that is depe ndent on the ambient temperature at which the lamb is maintained.