Vitamin D and manganese in the nutrition of the chick.

I . In two experiments with chicks given diets of different manganese content, the effects of vitamin D on the Mn contents of bone and liver and on the retention of 54Mn in bone, liver and the whole body were determined. 2. Vitamin D slightly increased the Mn content of dry fat-free bone but the proportion of Mn to ash remained unchanged and the Mn content of bone was influenced much more by the level of dietary Mn than by the presence of vitamin D. 3. Vitamin D, when given over a 3-week period, increased slightly the Mn content of the liver, but again the level of dietary Mn had a greater effect than the presence of vitamin D. 4. The retention of an oral dose of 54Mn was not uniformly influenced by vitamin D, but in birds given the high-Mn diet retention was reduced by vitamin D, indicating a decrease in the turnover of Mn.