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The Effect of Various Factors on the Vitamin D Content of Several Common Forages¹

Department of Dairy Husbandry, New Hampshire Agricultural Experiment Station, Durham

ABSTRACT

There is adequate evidence in the literature to prove the need for vitamin D by dairy cattle. Although direct solar irradiation can provide an animal with the antirachitic factor, the amount of vitamin D in the ration is of primary importance in determining the adequacy of this factor, particularly during the winter months. Because forage crops are the principal natural source of vitamin D in the ration of the cow, the need for vitamin D supplementation depends on the amount provided by the forage.

It has been believed generally that green forage plants are devoid of vitamin D and that this vitamin is formed in the plant upon exposure to sunlight after mowing. Unfortunately, the situation is not nearly as simple as this. As shown by Wallis et at. (10), the vitamin D content of different hays varies widely and cannot be predicted accurately on the basis of present knowledge.

¹ Published with the approval of the Director of the New Hampshire Agricultural Experiment Station as Scientific Contribution No. 166.