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Vitamin D Metabolites in Plasma of Cows Fed a Prepartum Low-Calcium Diet for Prevention of Parturient Hypocalcemia¹

Department of Animal Science, Iowa State University and National Animal Disease Center, Ames 50011

ABSTRACT

Our objective was to characterize changes in vitamin D metabolites of plasma in Jersey cows fed a prepartum low-calcium diet. Eight cows were fed a high-calcium diet (80 g/day) and eight were fed a low-calcium diet (8 g/day) at least 14 days before parturition. Calcium concentrations in plasma decreased after initiation of feeding either diet, but cows fed low-calcium diet tended to have lower prepartum calcium and phosphorus and greater peripartal calcium in plasma. Hydroxyproline in plasma was greater during peripartal period in cows fed low-calcium diet. Prepartum 1,25-dihydroxyvitamin D in plasma tended to be greater in cows fed low calcium. Increases in 1,25-dihydroxyvitamin D were only 2 and 3 days after initiation of the low-calcium diet; during the first 2 days after parturition, however, 1,25-dihydroxyvitamin D tended to be lower in those cows fed low calcium. As parturition neared, 24,25-dihydroxyvitamin D tended to be lower in cows fed the low calcium-diet. Usual early postpartum changes in calcium, phosphorus, magnesium, 1,25-dihydroxyvitamin D, and hydroxyproline were seen during first few days after initiation of feeding low calcium. Thus, we propose that the preventative action of the low-calcium diet is associated with preparation of the calcium homeostatic mechanism several days before the calcium demand of initiation of lactation.

¹ Journal Paper No. J-9822 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project 2185. This project was supported in part under Broad Forum Cooperative Agreement No. 12-14-3001-53 3 between Iowa State University and the National Animal Disease Center, Agricultural Research, Science and Education Administration, US Department of Agriculture.

² Lilly Research Laboratories, Division of Eli Lilly and Company, Greenfield Laboratories, P.O. Box 708, Greenfield, IN 46140.

³ National Animal Disease Center.

⁴ Department of Animal Science.

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