Relation between protein efficiency and net protein utilization

Abstract

Protein efficiency ratios (PER), g gain in wt/g protein eaten, and net protein utilizations (NPU), % fed protein retained, were calculated in rats for 32 proteins and 5 amino acid mixtures. Evaluation of protein by these methods correlated closely and agreed with data for the same proteins from different laboratories. Food intake could be correlated with nutritive value of proteins as measured by PER or NPU. For NPU the relationship was y2 = 67x -3891 (where y = NPU, x = g food intake/100 g body weight) and for PER y2 + 20y = 1.55x - 135.4. The relation between PER and NPU found with proteins did not hold for amino acid mixtures, due to the reduced consumption of the latter.