Thermoregulatory responses of restrained versus unrestrained rabbits.

Two male and one female New Zealand white rabbits were used in this study. At ambient temperatures of 20, 10, and 0° C, the animals were either lightly restrained with a Plexiglas collar or were unrestrained. Heat balance was zero during these experiments, as indicated by a stable rectal temperature.Heat losses due to vasomotor state and respiratory evaporative water loss were not significantly different between the restrained and unrestrained animals, whereas metabolism and heart rate were significantly higher in the restrained animals. Inappropriate posture, which is caused by the restraint, may be responsible for an increased energy expenditure at low ambient temperatures of as much as 32% of the resting heat production.