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Preparation of Roughage Samples for Biological Determination of Vitamin D Content

Laboratory of Animal Physiology, Agricultural University, Wageningen, Netherlands

ABSTRACT

A critical evaluation of existing techniques for assaying the vitamin D content of roughages was conducted, using the curative X-ray method on growing rats. Evidence was presented to show that mixing ground hay with the rachitogenic diet may give aberrant values as a result of the interaction of calcium, phosphorus, and vitamin D. A simple extraction of the hay sample did not remove all of the antirachitic activity. When the hay sample was pretreated with alcoholic KOH it was possible to remove the antirachitic activity quantitatively by petroleum ether extraction. Subsequent studies showed that the presence of a factor, identified as the carotene of the hay extract later on, depressed the curative effect of vitamin D. Removal of this substance by chromatography on alumina resulted in an extract free of the inhibitory factor. As a result of these studies, a modification of existing methods for determining the vitamin D content of roughages is presented.

¹ Present address: Department of Animal Husbandry, Cornell University, Ithaca, N. Y.