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

This study examined the effect of ambient temperature and feeding on b rown adipose tissue (BAT) function and thermoregulation in lambs born either vaginally at term or by Caesarean section close to term. Immedi ately after birth lambs were placed in a warm (30 degrees C) or cool ( 15 degrees C) ambient temperature and measurements of colonic temperat ure and heat production recorded for 6 h. Lambs were Fed 50 ml of colo strum when 5 h old. The amount of uncoupling protein and level of guan osine 5' diphosphate (GDP) binding in BAT was higher in vaginally deli vered lambs than in lambs delivered by Caesarean section. For each del ivery group, GDP binding was greater in lambs maintained at 30 degrees C than in lambs maintained at 15 degrees C. O-2 consumption, CO2 prod uction and colonic temperature only increased after feeding in lambs b orn by Caesarean section and maintained at 30 degrees C, a response th at was accompanied by a decreased incidence of shivering. Irrespective of delivery temperature, plasma thyroid hormone concentrations and no radrenaline content of BAT were lower in lambs born by Caesarean secti on than in those born vaginally. Plasma cortisol concentrations were h igher in lambs delivered by Caesarean section, as was adrenaline conte nt of BAT in these lambs maintained at 30 degrees C. It is concluded t hat the thermoregulatory response to feeding in terms of changes in bo th recruitment of shivering and colonic temperature were observed only in lambs delivered by Caesarean section.