It is well established that neonatal mortality is greater in the leaner commercial (CB) porcine genotypes compared to the ancient Meishan (MB) breed, which has a higher percentage of body fat. MB piglets, despite being considerably lighter at birth than commercial breeds, are resistant to hypothermia and hypoglycaemia. Pigs are one of the few mammals that do not express UCP1 which is used for heat production during the neonatal period. UCP2 is a mitochondrial protein proposed to be involved in energy metabolism. It is unknown whether an environmental challenge, such as a low temperature, would influence UCP2 expression in adipose tissue of newborn piglets. On the first day of life, piglets from 12 MB and 12 CB litters were ranked according to birth weight and the median piglet was randomly assigned to warm (MB n=6, CB n=6) (24°C) (W) or cool (MB n=6, CB n=6) (14°C) (C) treatment. In order to standardise milk intake, all piglets were given 3ml of commercial sow milk replacement. Colonic temperature was measured, piglets were placed in a temperature controlled chamber and maintained for 180 min after which time they were humanely killed with an overdose of barbiturate (100 mg kg^-1 pentobarbital sodium: Euthatal). UCP2 expression in AT was measured using RT-PCR as described previously (Mostyn A et al., 2004). Results are shown as means ±SEM; significant differences between breeds at each sampling age were assessed by GLM. Cool maintained CB piglets were colder than W maintained after 20 minutes (20 minutes W, 38.2±0.1; C, 37.3±0.4 °C (P=0.026)) an effect not apparent until 90 minutes in the MB piglets (90 minutes W, 38.7±0.2; C, 37.6±0.3 °C (P=0.004)). Environmental temperature had no effect on UCP2 expression in CB piglets, which had significantly higher UCP2 expression compared to MB, a difference which was greatest in C maintained (C: MB, 3.8±2.9; CB, 58.11±12.7 % of reference (P=0.019); W: MB, 44.1±13.5; CB 75.69±12.6 % of reference (P=0.037)). In conclusion, despite MB piglets having a substantially lower abundance of UCP2 compared to CB piglets, they have no difficulty maintaining a normal body temperature. UCP2 therefore does not appear to compensate for the absence of UCP1 in promoting heat production in neonatal piglets.