Further Studies on Protein and Energy Requirements of Chicks Selected for High and Low Body Weight

The study reported by Siegel and Wisman (1962) showed that chicks selected in divergent directions for body weight at 8 weeks of age responded similarly to changes in dietary energy and protein. The basal ration employed was of the starter-grower type and a constant Calorie-protein ratio (39.2) was maintained when the productive energy and crude protein levels were varied. The experimental plan also included a comparison with a more efficient broiler-type ration. Since the broiler ration elicited greater body gains in both the high weight and low weight lines, a subsequent study was undertaken to further observe responses to energy and protein changes using this ration as the basal (Ration D, Siegel and Wisman, 1962). The results are reported herein. Formulated to support maximum growth, such a ration should reflect energy and protein changes more precisely. The source of chicks and the experimental procedure were the same as in the…