Effects of Cholecalciferol on Bone Formation and Serum Calcium, Phosphate and Magnesium in Chicks

The purpose of this study was to examine the sequence of appearance of effects of vitamin D deficiency as well as a high daily intake of vitamin D on bone, blood and general growth. One-day-old male chicks were fed one of three diets that differed only in cholecalciferol content: none (D-deficient), 1.4 IU/g diet (control) or 70 IU/g diet (high-D). Body weight; serum Ca, PO4 and Mg; and lipid-free dry weight and percentage ash of the right femur were measured after the chicks were fed the diets for periods ranging from 3 days to 4 weeks. Compared to control chicks the body weight of D-deficient chicks was not significantly reduced until week 3, whereas that of high-D chicks was only slightly reduced at 4 weeks. The serum Ca of D-deficient chicks was decreased at 1 week and fell progressively thereafter, while the serum Ca of high-D birds remained normal for the entire 4-week period. At 2 weeks, high-D chicks had a decreased serum Mg level and a normal serum PO4 level, while D-deficient chicks had increased serum levels of both Mg and PO4. Percentage bone ash was reduced at 2 weeks in D-deficient chicks and increased at 1 week in high-D chicks. The data indicate that: 1) a high, but nontoxic, intake of vitamin D can stimulate bone mineral deposition in the presence of a normal serum Ca level; 2) early effects of vitamin D deficiency in the chick are hypocalcemia by 1 week and hyperphosphatemia and hypermagnesemia by 2 weeks; and 3) an inverse relationship exists between levels of serum Mg and dietary vitamin D.