Studies on the Vitamin D3 Requirement of the Broiler Chick

THE vitamin D3 requirement of the growing chick has been estimated by the National Research Council (1960) to be 90 I.C.U. per pound of feed. Recent studies by Waldroup et al. (1963b) indicated that dietary vitamin D3 levels of 360 I.C.U. per pound increased body weight and percent bone ash. However, the response to higher levels of this vitamin became less as calcium and phosphorus levels approached optimum. To gain additional information regarding the effect of increased vitamin D3 levels and the relationship of this vitamin to the calcuim and phosphorus content of the diet, three experiments were conducted under conditions of practical-type rearing as well as in battery brooders isolated from sources of ultraviolet light. Battery brooder studies—A factorial arrangement with two calcium levels (0.50 and 1.00 percent), two phosphorus levels (0.50 and 0.70 percent total phosphorus) and seven levels of vitamin D3 was used.…