Metabolism of calcium and phosphorus during pregnancy and lactation in white-tailed deer

The effects of pregnancy and early lactation on blood parameters were studied in 4 white-tailed does in 1981-82 and 8 in 1982-83. No year or fecundity effects (P less than 0.05) were found on plasma calcium (Ca), inorganic phosphorus (P), calcitonin (CT), parathyroid hormone (PTH), or oestradiol -17 beta (E2). An increase (P less than 0.05) in dry matter and metabolic feed intake occurred during pregnancy and lactation. Plasma Ca tended to increase during pregnancy and peaked 5-7 weeks pre-partum, while hypocalcaemia was observed 1-2 weeks pre-partum. Elevated concentrations of plasma Ca and P were found during lactation. During the last trimester of pregnancy, plasma concentrations of alkaline phosphatase (AP), PTH, and E2 but not of CT were higher (P less than 0.05) than in the other trimesters. The results indicate a physiological hyperparathyroidism in pregnant deer. Plasma concentrations of CT were higher (P less than 0.05) during lactation and post-weaning than during pregnancy. Increased AP and PTH during late pregnancy may be responsible for Ca absorption and mobilization, whereas elevated plasma concentrations of E2 may function to block excessive bone resorption. After parturition, lowered E2 may allow bone resorption to proceed, relatively high PTH may enhance Ca absorption and mobilization, and elevated CT may protect the skeleton against excessive bone resorption.