Changes in food intake in response to alterations in the ambient temperature: modifications by previous thermal and nutritional experience.

1. The influence of ambient temperature on ad libitum food intake has been investigated in piglets weaned at 2 weeks and kept in the hot (35 degrees C) or the cold (10 degrees C) on a high or low energy intake for 6 weeks. Further, the extent to which food intake was correlated with fasting body temperatures and resting metabolic rate was also examined. 2. The amount of food eaten in a single meal was recorded daily in two series of tests. In Test I, measurements were made both at the normal living temperature and after 2 and 24 h at thermal neutrality (25 degrees C). In Test II, the animals were examined at 25 degrees C over a 4 day period. Resting metabolic rate and body temperatures were also measured, immediately before the measurement of food intake. 3. Food intake was much greater at 10 than at 35 degrees C, but even at thermal neutrality it was significantly higher for those which had been in the cold. This was true for periods of between 2h and 4 days at 25 degrees C. Although food intake was not correlated with skin or core temperatures, there was an indication of a correlation with metabolic rate, particularly at thermal neutrality. 4. The results show that long-term cold exposure has a lasting effect on food intake, even at thermal neutrality, and it is suggested that this may be related to hormonal changes.