Effect of Energy Intake on the Biological Value of Protein Fed to Rats

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Abstract
Biological values of soybean oil meal protein and of methionine-supplemented blood fibrin were determined with 30 weanling male albino rats by the nitrogen balance procedure. Each protein was incorporated into otherwise complete diets at a 10% level. Food intake was regulated at 4.0, 6.0 or 8.0 gm daily. It was found that at 4.0 gm food intake the biological value of soybean protein and of methionine-supplemented fibrin was 59.1 and 74.3, respectively. At 6.0 and 8.0 gm of food intake the values did not vary significantly between intake levels and averaged 71.0 and 96.8 for the two proteins. The low biological values obtained at 4.0 gm intake are ascribed to utilization of a portion of the dietary protein for energy to support weight maintenance of the animals.