The Utilization of Energy Producing Nutriment and Protein as Affected by Individual Nutrient Deficiencies

Abstract

The effects of four planes of protein intake (10, 15, 20 and 25 per cent) were studied by means of two 10 weeks' growth, metabolism and body analysis experiments on forty-eight albino rats each. The rats for each experiment were selected as twelve groups of four individuals, each such group being of one sex and of the same litter, and each rat in each such group received the same energy but different protein intake. There were, therefore, twelve rats on each treatment in each experiment. The effects of the increasing protein content of the equicaloric diets were as follows: Increase in gain in body weight, at decreased cost in terms of dry matter of food; increase in efficiency of digestion and retention of protein and of energy-producing nutriment; increase in urinary nitrogen at an increasing rate, and increase in protein of the body at a decreasing rate; increase in energy of the urine coincident with decrease in the energy of the feces, the metabolizable energy, therefore, remaining practically constant; diminishd efficiency in the utilization of food nitrogen; no regular change in amount of fat gained, but usually a decrease in fat gained in proportion to protein gained. Increases in the protein of equicaloric diets having the effect to improve their nutritive balance made no change in the basal heat production per unit of computed surface area, but diminished the total heat production of the animals, as they lived under normal conditions of freedom of activity.