Unidentified Growth Factors Required by Chicks and Poults

THE availability of vitamin B12 for use in experimental work following its isolation by Rickes and co-workers (1948) and Smith (1948), has made possible further progress in the study of unidentified dietary factors required for rapid growth of the chick and poult. Ott et al. (1948) found that under their experimental conditions crystalline vitamin B12 produced a growth response comparable with that obtained with various crude supplements of animal origin. Lillie et al. (1948) confirmed these observations and obtained a similar response from cow manure factor concentrates described by Rubin and Bird (1946). Nichol et al. (1949) also reported that vitamin B12 was as effective in promoting chick growth in their studies as condensed fish solubles or injectable liver preparations. Thus, much of the unexplained growth-stimulating activity obtained with materials primarily of animal origin can be attributed to their vitamin B12 content. It is extremely difficult, however, to explain entirely . . .