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Vitamin D Physiology and its Importance in Dairy Cattle: A Review¹

Department of Dairy and Poultry Science, Kansas State University, Manhattan 66506

ABSTRACT

High milk yields make considerable demand on calcium and phosphorus metabolism in the dairy cow. Vitamin D plays a major role in calcium metabolism and, hence, indirectly in phosphorus metabolism. Too often vitamin D has been neglected in current dairy cow nutrition. Several factors including high energy rations, high milk production, and use of exotic rations indicate a need to reevaluate vitamin D nutrition for high producing cows.

In rations with sufficient calcium, adequate vitamin D promotes positive body balance, but natural sources may provide insufficient vitamin D in many high-energy, low-roughage rations. Recent discoveries of vitamin D metabolites and their role in calcium metabolism have spurred related basic research. Knowledge of vitamin D/calcium metabolism may have practical value in treating and preventing parturient paresis as well as in nutrition per se. In addition, vitamin D may be related to reproductive performance via enhanced psychic estrus expression. Finally, the knowledge of vitamin D in contemporary dairy cattle nutrition is simply less complete than many believe.

¹ Contribution 887, Dairy and Poultry Science Department, KAES, KSU, Manhattan.