Further Information Concerning Unidentified Chick Growth Factors

THE existence of unidentified growth factors for chicks and turkey poults has been known for some time. Reed et al. (1951) confirmed the postulate of Berry et al. (1943), Hill et al. (1944) and Hill (1948) as to the existence of a chick growth factor in dried whey which has been termed the “whey factor.” Additional work (Carlson et al., 1949; Heuser and Norris, 1951; Couch et al., 1952; Fuller et al., 1952; and Sunde et al., 1952) has led to the establishment of the existence of a growth factor or factors in fish meal and fish solubles which has been designated as the “fish factor.” This factor is different from the “whey factor” as indicated by the supplementary relationship that has been found when the two factors were added simultaneously to a broiler ration. The data from this Station (Couch et al., 1952) have been obtained under practical conditions, …