NITROGEN UTILIZATION IN CALORIC INSUFFICIENCY

Abstract

To determine whether a portion of ingested protein can be used for tissue growth when insufficient calories were fed, isocaloric and suboptimal amounts of calories in the form of dextrose or as dextrose and protein hydrolysate (amigen®) were fed to protein-depleted, partially starved, scalded and normal stock rats together with adequate vitamins and minerals. It is concluded that: 1. The greater the need for protein, the greater is the utilization of ingested nitrogen for new protein synthesis under conditions of caloric limitation. Protein-depleted rats are able to build new protein tissue even when basal energy requirements are not completely supplied. 2. Protein depleted, partially starved, scalded and stock animals retain or gain more weight when fed adequate or suboptimal quantities of the hydrolysate-dextrose diet than when fed isocaloric quantities of the dextrose diet. 3. Stock animals with no pre-existing protein loss, and in good nutritive condition, do not utilize dietary nitrogen for tissue building when the caloric intake is suboptimal. 4. When the caloric intake is less than that required to meet the estimated basal energy needs, a diet supplying approximately 20% of the calories as protein supported better growth than those supplying more or less than this amount.