Method for Determining Amino Acid Adequacy of Liquid Protein Hydrolysates in Rats

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Abstract
Near adult male rats were fed a purified protein-free diet for 12 days to deplete their protein reserves. When a 5% soln. of a partial acid hydrolysate of fibrin was then fed ad libitum, the rats consumed 50 ml./day or more and gained about 60 g. in 12 days. The N intake was generally limited to 240 or 320 mg./day. Failure of certain hydrolysates to give max. responses was associated with limiting amino acid deficiencies revealed by chemical and micro-biologic assays. Solns. of mixtures of pure amino acids patterned after casein, but adjusted to compensate for insolubility of certain of the amino acids, gave a max. rate of repletion, somewhat greater g. N than the avg. response to casein. When 1 of the essential amino acids was omitted from such an amino acid mixture, the rats refused to drink the soln., except in small amts. to satisfy thirst, and lost wt. rapidly. The method appears to provide a basis for rapid and convenient estimation of the essential amino acid adequacy of liquid hydrolysates when taken orally.