Abstract NIACIN is known to be required by several species of animals including poultry. However, the quantitative requirement of mature chickens is unknown. The Committee on Animal Nutrition of the National Research Council in its 1960 revision of the nutrient requirements of chickens, was unable to make a recommendation for a niacin requirement standard for laying and breeding hens because of lack of information. Dann and Handler (1941) and Snell and Quarles (1941) reported niacin synthesis by the developing chick embryo to the extent that the hatched chick contained ten to twenty times as much niacin as the unincubated egg. Briggs et al. (1942, 1943, 1945, 1946), in a series of papers reported that niacin is essential in the diet of the chick for optimal growth and to prevent “chick black-tongue”; described the symptoms of niacin deficiency in the chick, and concluded that tryptophan may replace niacin in purified diets for…