Vitamin D in the blood of sheep

The vitamin D content of the tissues of mammals and birds is believed normally to be too small to be determined by any chemical method at present available.Information on the matter can be obtained only from biological assay; as this is laborious and time-consuming, it is perhaps understandable that few results have been recorded.The only published values for sheep are those of Warkany (1937), 46-67 i.u./Ioo ml plasma.It is not clear in which tissues, if any, there is long-term storage of vitamin D. Heymann (1937) gave rabbits a large dose of vitamin D, 200000 i.u., and assayed the vitamin D in various tissues of animals killed at intervals up to 12 weeks after dosing.