Dependence of Biological Value on Protein Concentration in the Diet of the Growing Rat

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Abstract
The biological values and the ratio of nitrogen balance to absorbed nitrogen of whole egg, casein and peanut meal proteins were determined at concentrations between 4 and 29% of the diet, employing young albino rats as experimental subjects. The relationship of biological value and protein concentration was linear for all data except 4 and 8% egg protein, and the equations expressing this are: Y = 126.5 — 2.73X; Y = 96.1 — 1.78X and Y = 75.3 — 1.35X, in which Y is biological value and X is percentage of protein in the diet, for egg, casein and peanut meal, respectively. The ratio of nitrogen balance to absorbed nitrogen was found to be best described by the following equations: Y = 1.23X — .065X2 — 1.085 for egg, Y = 0.89X — 0.038X2 — 0.93 for casein, and Y = 74X — 0.041X2 — 0.90 for peanut meal proteins, in which Y is nitrogen balance and X is nitrogen absorbed, both expressed in milligrams of nitrogen per gram body weight raised to the ¾ power.