Investigation of body temperature as a possible feeding control in the suckling rat.

Under natural conditions, rat pups are deprived of milk only when the dam leaves the nest. At this time the body temperatures of the pups will fall. In this study we have investigated the possibility that lowered body temperature of the pups stimulates behavioral changes in either the pups or the dam, leading to increased milk intake. To study behavioral changes of the pups, the milk intake of warm-fasted, cool-fasted, and fed littermates was compared to 10, 14 and 16 days of age. There was no effect of body temperature on milk intake at any age. To study behavioral changes in the dam, milk release by dams suckling entire cool litters was compared with that by dams suckling entire warm litters. Milk release was not significantly affected by the litter temperature. We conclude that lowered body temperature of suckling rat pups does not cause increased milk intake.