Assay of Dry Proteins by Rat Repletion Method. Nutritive Value and Amino Acid Composition of Six Reference Proteins

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Abstract
Six reference proteins obtained from Rutgers University as part of a collaborative test program, plus fibrin and lactalbumin, were assayed by the rat repletion method as supplements separate from a non-protein diet. Feeding levels of 0.12 and 0.24 gm N per rat per day were studied. The repletion response to the reference proteins was roughly in the following order: egg albumin, defatted whole egg, defatted beef muscle and casein about on a par, peanut flour, and wheat gluten. Fibrin and lactalbumin compared favorably with the egg proteins. The weight responses were related to the essential amino acid composition of the reference proteins. The advantages and limitations of the method are discussed, together with the significance of the data obtained. A convenient method for routine control of the protein value, wherein rats are reused many times, is described.