Abstract INVESTIGATIONS at many research institutions have shown that rations made primarily from plant products may be satisfactory for egg production but fail to support maximum hatchability. This deficiency was corrected by supplementing the plant-products rations with animal protein concentrates, such as liver, fish meals, condensed fish solubles, meat scraps, dried skimmilk, and casein (Byerly, Titus, and Ellis (1933), Gillis, Heuser, and Morris (1942), Wilgus and Zander (1944), Cravens, Halpin, and McGibbon (1946), Bird et al. (1946), Heuser et al. (1946), Bethke and associates (1946-a), and Petersen, Wiese, and Lampman (1948). Evidence has been presented by Bethke and associates (1946-b, 1947) that the factor present in animal protein concentrates essential for hatchability is not choline, riboflavin, methionine, pantothenic acid, pyridoxine, niacin, biotin, or folic acid. It has also been reported that the addition of dried cow manure or an acid precipitate of a water extract of cow manure to an all-plant . . .