Changes in Periparturient Plasma Parathyroid Hormone and 1, 25-Dihydroxyvitamin D Levels in Cows with Milk Fever History

Abstract

Periparturient plasma calcium (Ca), parathyroid hormone (PTH) and 1, 25-dihydroxyvitamin D [1, 25-(OH)₂D] levels were evaluated in 8 cows with milk fever history (historied cases) and 5 cows without the history (controls). The lowest plasma Ca level was recorded around delivery in both historied cases and controls. Decreased levels of plasma Ca were lower in the 5 historied cases than those of the controls, and one of historied cases developed milk fever, in which the decreasing of plasma Ca levels persisted in spite of the immediate elevation of plasma PTH and 1, 25-(OH)₂D values. Although this hypocalcemia recovered after the Ca therapy, plasma Ca value was repeated to decrease at 2 days after the clinical onset associated with an additionally greater elevation of plasma 1, 25-(OH)₂D levels.