The effect of enzymatic hydrolysis on the nutritive value of casein; intravenous feeding in dogs.

Studies by Christensen et wl. (1, 2) and by -4llison and associates (3) have demonstrated that the urinary excretion of peptides is greater than the urinary excretion of free amino acids following the infusion of partial hydrolysates of casein or of fibrin. Christensen and coworkers have shown also that infusion of these hydrolysates results in a greater persistence of peptides in the plasma than of free amino acids. Their results were interpreted to mean that in a given hydrolysate peptides are not as well or as quickly utilized as free amino acids, although some peptides may be more readily utilized than others (2). The following studies were planned to determine the effects of varying the degree of hydrolysis of casein by pancreatic enzymes from 18 to 40 to 60 per cent, on the excretion of peptides in the urine, and on the retention of nitrogen in the animal. These enzymatic hydrolysates were found to have approximately the same contents of the ten essential amino acids and they, therefore, differed from one another only in the proportion of free amino acids and polypeptides. Enzymatic hydrolysis was used so that the destructive forces of other forms of hydrolysis on certain amino acids would be minimized.