EVALUATION OF PROTEIN IN FOODS: VII. FACTORS INFLUENCING NET PROTEIN UTILIZATION AS DETERMINED BY CARCASS ANALYSIS

Abstract

The effects of deficiency of vitamins and minerals on net protein utilization (N.P.U.) values obtained with casein at various protein levels were studied in growing male rats. Animals given diets without added vitamins and minerals lost weight and had reduced N.P.U. values. Carcass analysis data indicated that nitrogen retention occurred in these animals concomitantly with loss of body water and fat. In further studies, a direct relationship was observed between N.P.U. values and the dietary lysine content, at lysine concentrations varying from 0.32 to 0.72%. The use of various control groups to estimate endogenous and metabolic nitrogen losses gave similar N.P.U. values.