Effect of Parathyroid Hormone on Calcium and Other Plasma Constituents of Dairy Cattle near Parturition

Abstract

Abstract The administration of parathyroid extract within 2 hr postpartum to first calf heifers, normal mature cows, and mature cows with a past history of milk fever did not appreciably alter the plasma levels of calcium, magnesium, or alkaline phosphatase. Plasma inorganic phosphorus was increased moderately in most of the animals by the action of parathyroid extract. At the time of parturition mature animals showed a greater decrease in calcium and inorganic phosphorus and a greater increase in magnesium than did the younger animals. Alkaline phosphatase remained relatively constant in all animals. Thirty-one parturitions were studied and six cases of milk fever observed. Data suggest that milk fever can result from either a low level of calcium or a low level of both phosphorus and calcium. Cases of milk fever which relapsed were of the latter type. Parturient cows were not responsive to parathyroid extract and its administration just after calving had no apparent effect on the occurrence or severity of milk fever.