The Provitamin A Requirement of Growing Chickens

A SURVEY of the literature on the vitamin A requirements of the growing chick revealed that at least eight papers on this subject have appeared since 1926. (Almquist and Meechi, 1939; Bearse and Miller, 1937; Biely and Chalmers, 1936; Record, et al. 1937; Ringrose and Norris, 1936; Sherwood and Fraps, 1936; Tepper and Durgin, 1938; Wilson, et al. 1936). These papers were examined with the following criteria in mind: (1) Practicality of the ration used, (2) Nutritional adequacy of the ration, except for vitamin A, (3) The number of birds per test group, (4) The attainment of what might be considered normal weight at 8 weeks of age, (5) The presence of a group whose growth response is less than normal, (6) The use of a practical source of vitamin A or carotene, and (7) relatively small differences between levels of vitamin A. None of the experiments noted met all . . .