Decrease in body temperature and locomotor activity as an adaptational response in piglets exposed to cold on...

Littermate piglets weaned at 14 days of age were acclimated at 10 degrees C. During six weeks of the experiment half the littermates, OP, were able to make an operant response for heat, the control half, CP, could obtain only light. The piglets were fed in such a way that CP gained weight very slowly. OP maintained a high ambient temperature, and increased body weight by 134%, while CP by 40% (p less than 0.001); food efficiency (weight gain/food intake) was 0.66 for OP and 0.25 for CP (p less than 0.001). Rectal temperature, Tre, of OP was maintained at 38.3 degrees C, and that of CP at 36.7 degrees C (p less than 0.001). Locomotor activity of OP was 137% higher (p less than 0.001) than that of CP. During a one-day access to an operant heater, or a one-day period of unrestricted feeding, CP increased Tre and locomotor activity to values observed in OP. By the end of the experiment CP had shorter bodies, tails, snouts and smaller ears than OP. The proportion of skin with attached fat was higher in OP than CP. It is concluded that restrictions imposed on thermoregulatory behaviour and on thermogenic capabilities of the autonomic system resulted in a lowered body temperature and locomotor activity as cold defence responses in young pigs.