Net Protein Values for the Growing Chicken as Determined by Carcass Analysis: Exploration of the Method

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Abstract
A nitrogen retention method for use in the growing chicken has been outlined, based upon one originally described by Bender and Miller (′53) for the growing rat. The method involves the feeding of 13% protein rations together with a nitrogen-free ration to quadruplicate groups of 5 birds. It was shown that the carcass water:nitrogen ratios were remarkably constant despite considerable variations in nitrogen and fat content of the carcass on various diets. The net protein value of isolated soybean protein decreased linearly with increasing level of dietary protein over the range of 13 to 27%. Five protein sources were studied of which isolated soybean and soybean meal protein were observed to be of comparable value. A commercial sample of defatted egg powder was noted to be below expectation. Peanut meal protein was very poorly utilized even when supplemented with methionine and lysine.