Self-selection of a high calcium diet by vitamin D-deficient lactating rats increases food consumption and milk production.

Lactating and nonlactating rats, both deficient and replete in cholecalciferol, were allowed a free selection among three diets containing 0.47% Ca, 0.3% P (normal Ca, normal P diet); 2.0% Ca, 0.3% P (high Ca diet); and 0.47% Ca, 1.0% P (high P diet). An additional group of vitamin D-deficient lactating rats was fed only the normal Ca, normal P diet. Vitamin D-deficient rats showed a strong selection preference for the high Ca diet but avoided the high P diet, whereas cholecalciferol-replete rats consumed the normal Ca, normal P diet predominantly. Compared to the nonselecting rats, the selection of the high Ca diet by the lactating rats deficient in vitamin D resulted in an increase in plasma calcium levels, hypophosphatemia, a doubling of food consumption, a reduction in maternal body weight loss and a stimulation of milk production as indicated by pup growth. These results demonstrate that vitamin D-deficient rats select a high Ca diet and that the decrease in milk production found in vitamin D deficiency results from a decrease in food consumption and that this anorexia is at least partially dependent on the hypocalcemia normally occurring in vitamin D deficiency.