Vitamin D Content of Roughages

Abstract

Very little vitamin D generally is considered to exist in the green growing plant. Ergosterol or some other provitamin is present and may be changed over to vitamin D when the plant is cut and exposed to the radiant energy of the sun, as in the sun curing of roughages. From this viewpoint it could be assumed that flue or barn-cured hay would have less vitamin D than sun-cured hay and that little or no vitamin D would be present in roughages cured in the dark or artificially dried with no sun exposure. However, this is not the case according to results obtained at this Station. Assays made on sun-cured and barn-cured hays show practically equal amounts of vitamin D in the two hays. Furthermore, appreciable amounts of vitamin D arc present in hays dried without exposure to the sun, as in a dehydrating machine or natural-drying in a dark place. A few trials at other stations have been reported showing that the nutritive and antirachi~ic values of barn-cured hay compare favorably with that of sun-cured hay for dairy animals, as based on such criteria as rate of growth, physical condition and analyses of certain bones from slaughtered animals. However, no vitamin D contents of the hays were given. Wylie et al. (8), in a trial with yearling heifers, compared the feeding value of barn-cured hay with that of sun-cured hay. The feeding periods extended through three successive winters, each trial being 150 days in length. Each animal received daily 2 lb. of grain, 10 lb. of corn silage and hay ad libitum. The heifers in both groups made normal growth with no marked difference in favor of either. Moore and Thomas (4) report the results of a feeding trial with dairy calves comparing the antiraehitic values of field-cured alfalfa hay, barndried alfalfa hay and wilted alfalfa silage. They used three groups of dairy calves, six in each group. The calves were first depleted of their body stores of vitamin D and then fed on the above roughages for a period of 6 months. From the results obtained, it was concluded that further fundamental work is necessary. The indications to date are that barn-dried hay and wilted silage will provide sufficient vitamin D for normal functions in growing calves when fed at the usual levels of roughage feeding, i.e., at the rate of 2 to 3 lb. of hay, or the equivalent, per 100 lb. of body weight. EXPERIMENTAL