PREVIOUS DIETARY PROTEIN LEVEL AND SURVIVAL OF STARVING RATS IN THE COLD

The effect of the level of dietary protein (5%, 20%, 40% casein by weight) fed for 7 days in an environmental temperature of 22 °C, upon the survival of rats subsequently starved in an environmental temperature of 2 °C was studied. In these experiments ad libitum feeding, isocaloric feeding, and restricted feeding techniques were used, and the effects of thyroidectomy and thyroid feeding were investigated. In all cases, animals provided with the 5% protein diet survived for shorter periods than did those fed the 20% protein diet. In intact rats, but not in thyroidectomized rats, survival time appeared to be inversely related to rate of body weight loss in starvation. Differences in duration of survival among dietary groups are not explicable on the basis of differences in body weight, body composition, or total food intake prior to starvation. The results of experiments using thyroidectomized rats and thyroid feeding suggest that the effect of dietary protein level upon survival in subsequent starvation in the cold are not mediated through the thyroid gland.