Abstract
Weanling rats were fed diets containing three different proteins, lactalbumin, casein and soy protein, each fed at levels from zero to over 50% of the diet. Response was measured as total body water in relation to protein consumption. The data confirmed the hypothesis that protein utilization in young rats is constant over an appreciable range of intakes from the maintenance levels to those which allow near maximal growth. Thus it is concluded that the Miller and Payne concept, to the the effect that efficiency of protein utilization for growth declines continuously with increasing dietary protein level, is usually erroneous.