Effect of Environmental Temperature on Utilization of Dietary Protein by the Growing Rat

Abstract

It has been shown that, provided the energy intakes of animals are below a certain physiological maximum, the thermogenesis resulting from cold exposure is accompanied by an increased food consumption, and an improved growth and N balance as compared with animals at thermal neutrality. Under these conditions, efficiency of protein utilization, rate of total endogenous N loss, and the energy cost of protein synthesis were shown to be unchanged. When the temperature, and dietary regimen were such that the animal's maximum food intake was inadequate to meet its energy needs for growth and thermogenesis, the efficiency of protein utilization was reduced as compared with that at normal temperatures, in a manner analogous to the reduction observed at restricted caloric intakes. Equations are presented, for prediction of effective protein values of diets under conditions of caloric restriction and reduced temperature. The significance of these observations is discussed in relation to the optimal conditions for efficient feeding of livestock, and also the standardization of conditions under which measurements of protein quality should be made.