Dietary Calcium and Phosphorus Levels and the Vitamin D Requirement of the Chick

IN THE course of experiments on the stability of vitamin D in practical poultry rations, it was found that the high mineral content of the rations masked any effect of different levels of vitamin D. The present experiments were undertaken therefore, to study the influence of the calcium and phosphorus content of the diet on the vitamin D requirement of the chick. Bethke et al. (1929) studied the effect of varying the Ca:P ratios in chick diets containing no vitamin D. They were able to grow chicks to 13 weeks of age on vitamin D-free diets but growth was poor and the incidence of leg weakness was high. There was some indication that at favorable Ca:P ratios, increasing the level of mineral favored growth and calcification. Hart et al. (1930) confirmed the results of Bethke et al., and grew chicks to 12 weeks of age on vitamin D-free diets. Again . . .