Analysis of a conflict between palatability and cold exposure in rats.

Rats were trained to feed each day from 10 o'clock to 12 noon. Once a week in an environment of Ta--15 degrees C, additional food was made available 16 m from a thermoneutral refuge. The additional food offered was either shortcake, meat pâté, peanut butter, Coca-cola, all of these (cafeteria), or laboratory chow. Although laboratory chow was also always available in their thermoneutral home, rats invariably ran in the cold to the feeder, especially so when the food offered was highly palatable. With such foods, animals took as much as half their nutrient intake in the cold. For less palatable food, rats went only once or twice to the feeder, and there ate little. The attractiveness of the various foods was ranked similarly by the amount eaten, the number of excursions to the feeder, and the time spent feeding in the cold. Meal duration and speed of running to the food were not influenced by palatability. For the whole group, the preference was: shortcake, Coca-cola, meat pâté, peanut butter, and chow. There was a considerable variation between rats in their attraction to different foods. Feeding behavior in a situation of conflict could be used to measure palatability.