Calcium Homeostasis in the Normal and Thyroidectomized Bovine

Abstract

In three thyroidectomized mature dairy cows daily intramuscular injection of a very small dose of vitamin D₃ (200,000 u/day/animal for six days) induced a slight but significant hypercalcemia and hyperphosphatemia which did not appear in three control cows. In three thyroidectomized steers, a physiological dose of parathormone (40 ng/min/kg for 7 hrs) or a very slight increase in daily calcium intake (40 gm/day/animal) induced a highly significant increase in plasma calcium: similar treatments had no effect on the calcemia of control steers.

Key words

Bovine - Calcium - Calcitonin - Parathormone - Phosphorus - Vitamin D.