T HE energy requirement of growing chicks has been studied in two widely different ways. One method is illustrated by the studies of Mitchell, Card and Hamilton (1931) who estimated the net energy requirements for maintenance and growth from the determination of basal metabolic rate and changes in body composition. Data of this kind have been of limited usefulness because of the lack until relatively recently of net energy values for poultry feedstuffs.The other method was used by Robertson, Miller and Heuser (1948) and Panda and Combs (1950). They studied the relationship between productive (net) energy of the ration and early growth rate to determine the minimum energy level per unit weight of the ration necessary to promote the maximum rate of growth. Both of these groups concluded that the minimum productive energy level required for maximum early growth rate was approximately 800-850 Calories per pound of ration on the basis of the productive energy values of poultry feedstuffs as reported by Fraps (1946). The experiments to be described in this paper were undertaken to obtain further information on the minimum dietary energy level necessary for maximum early growth rate of chicks. EXPERIMENTAL PROCEDUREAll of the experiments to be described

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S TUDIES of the effects of différent dietary energy levels in the nutrition of laying hens hâve been limited. Heuser and coworkers (1945) were among the first to show that rations low in fiber content supported a higher rate of egg production than similar rations high in fiber content. Bird and Whitson (1946) studied layer rations of high and low fiber content with respect to productive efficiency and showed that efficiency was related inversely to fiber content. They were the first to use the Byerly (1941) partition équation to calculate expected feed requirement as a basis for estimating the relative efficiency of rations. Using a similar procédure, Lillie and coworkers (1952) observed a marked improvement in the efficiency of egg production from the use of lard. Singsen, Matterson and Kozeff (1952) and Gerry (1954) hâve reported higher efficiency, measured as feed requirement per dozen eggs produced, with rations high in energy value as compared with low energy rations.The studies to be reported were undertaken to détermine the quantitative relationships of dietary energy level to rate and efficiency of egg production, using various grains and grain products and inedible animal fat to formulate rations containing widely différent energy levels.

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