Effect of diet and temperature acclimation on thermoregulatory behaviour in piglets

Piglets were weaned at 14 days and acclimated to 10 or 35 degrees C and kept either on a low or a high plant of nutrition. After 2 and 3 weeks of acclimation their operant thermoregulatory behaviour was observed at 15 degrees C. The pigs which had been living at 10 degrees C obtained more radiant heat than those from 35 degrees C and the animals on a low energy intake obtained more reinforcements than those on a high intake. There was no interaction between temperature and diet indicating that these two variables exerted their influence independently. Pigs tested 22 hr after a meal obtained more heat than when tested 1 hr after a meal. Rectal temperature before the test was significantly lower in the animals reared at 10 than at 35 degrees C, but the difference had disappeared at the end of the trial. By contrast, the pigs kept on different planes of nutrition had the same rectal temperatures before the test trial but afterwards the animals on a high diet had higher rectal temperatures. Body temperatures seemed to be the factor which influenced the demand for heat. The role of thermal comfort, body size, diet induced thermogenesis and separate sets of controls for autonomic and behavioural thermoregulatory responses in operant thermoregulatory behaviour is discussed.