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Rate of Vitamin D Formation in Hay¹

Vermont Agricultural Experiment Station

Abstract

The main sources of vitamin D for cattle are roughages and exposure of animals to direct sunshine. Since our northern climate is composed of short summers and long winters, many calves do not receive much sun exposure until 8 or 9 months of age. Therefore, roughages, especially hays, are of prime importance in providing sufficient amounts of this vitamin for growing cattle.

Theoretically, no vitamin D is considered to be present in the green growing plant. However, as soon as it is cut and exposed to the radiant energy of the sun, the provitamins present, such as ergosterol, are changed to the vitamin. Little is known regarding the rate of this transformation. How soon after cutting the hay crop does any appreciable amount of vitamin D occur?

Previous work by Newlander (1948) showed barn-cured hay to have practically as much vitamin D as sun-cured even though left in the field for only approximately 24 hours as compared with 48 hours for the field-cured hay.

¹ Journal Series Paper No. 22, Vermont Agricultural Experiment Station.