STUDIES IN PROTEIN NUTRITION OF THE CHICK I. THE INFLUENCE OF DIFFERENT PROTEIN CONCEN TRATES ON THE GROWTH OF BABY CHICKS, WHEN FED AS THE SOURCE OF PROTEIN IN VARIOUS SIMPLIFIED DIETS By

the past three years we have been engaged in investigations con-cerning the comparative value of various commercial protein concen trates as nitrogenous feeds in the poultry ration, particularly in regard to their influence on reproduction. In the course of this work it became evi dent that to further our knowledge of the dietary requirements for repro duction in the chick, we had to conduct our feeding trials under more carefully controlled conditions. At this time several workers had reported the successful growing of chicks under laboratory conditions, the food re quirements being covered by synthetic diets. We decided to avail ourselves of this information and to determine first the comparative growth value of these protein supplements when fed as the sole source of protein in an otherwise synthetic diet. The present paper presents some of the difficul ties which we have encountered, showing that our present concept of synthetic diets for chicks is quite inadequate. The protein feeding stuffs studied were buttermilk powder, fish meal, cod-liver meal and two abat toir by-products, meat meal and tankage. EXPERIMENTAL Our objective was to procure a synthetic basal diet, which, while satisfy ing the vitamin requirements, etc. of the chick, contained the minimum amount of protein and to supplement this diet with equal amounts of crude protein from the different protein supplements. A review of the literature revealed that our greatest difficulty in using a synthetic basal diet was to prevent the incidence of leg-weakness. Hart, Halpin and Steen-bock (1920) found that lack of a suitable roughage in the diet was the major cause of leg-weakness and that normal chicks could be grown on