Reinvestigation of the Vitamin A Requirements of Laying and Breeding Hens and Their Progeny

ON THE basis of the available evidence from quantitative studies, the Committee on Animal Nutrition of the National Research Council (1954) has estimated the vitamin A requirements to be 1,200 U.S.P. units per pound of diet for growing chickens, and 2,000 U.S.P. units per pound of diet for laying and breeding hens. The results of individual studies on which these estimates are based have varied widely. The sources of vitamin A activity used in the various studies on requirement were fish oils, alfalfa meals and/or yellow corn, all of which were unstable to some degree, especially after mixture in the experimental diets. Even with the precaution of frequent diet mixing, the instability of the vitamin or its precursors introduced considerable uncertainty into the quantitative estimates of requirement. Recently, efforts in industry have been directed toward the development of vitamin A preparations which are highly stable in diet mixtures and under…