Development of thermoregulation and neonatal survival in pigs

Neonatal mortality is still a source of serious loss to the swine industry. We know that optimal development of thermoregulation is a prerequisite of utmost importance for successful adaptation to extra-uterine life. Indeed, a comprehensive knowledge of piglet thermoregulation is now available and may be helpful to increase our understanding of the biology of neonatal losses. The newborn pig is poorly insulated and maintenance of its homeothermic balance depends essentially on its capacity to produce heat. However, unlike most newborn mammals, piglets do not possess brown adipose tissue and rely almost exclusively on shivering thermogenesis for thermoregulatory purposes. Therefore, skeletal muscle plays an essential role in preserving homeothermy. Key factors involved in the limited cold tolerance of the new-born and enhancement of thermoregulatory abilities early after birth have been identified. Most of them, and especially the maturation of skeletal muscle metabolism and function are suggestive of the relative physiological and metabolic immaturity of piglets at the time of birth. Therefore, physiological, biochemical, molecular and ultrastructural adjustments involved in the maturation of skeletal muscle energy metabolism after birth are presented. Finally, effects of key factors such as birth weight, genotype, colostrum intake, hypothermia and hypoxia on thermoregulatory abilities are described. (C) 2002 Elsevier Science B.V. All rights reserved.