The vitamin D activity of pastures and hays

There is not much information about the vitamin D content of fodders and hay.Most of it is from the United States and, more recently, Holland.Keener (1954) and Weits (1956) have summarized the available information.No such assessments apparently having been made in this country, an opportunity was taken to make a systematic study of the vitamin D activity of Scottish hill pastures.Monthly samples were obtained from one pasture during the sheep-grazing period in 3 consecutive years, and the vitamin D activity of the grass fat was determined.While this investigation was in progress experiments were begun at Shinfield to compare the nutrient content of hay made by the orthodox use of the pick-up baler (ground-cured) or on tripods with that of the original sward (Murdoch, Foot, Hosking, Line & Rowland, 1959; Thompson, 1959).Vitamin D assays were done on some of the samples and the results are also reported here. EXPERIMENTALCollection and drying of samples Scottish hill pastures.Samples were obtained at Netherphawhope from a hillside plot permanently surrounded with wire netting to keep off sheep.A representative sample was cut, with sheep-shearing shears, once a month from May to November in 1952 and from April to November in 1953 and 1954.Samples were brought straight back to the laboratory, spread on paper on a floor and stirred and turned periodically for 3 or 4 days until dry enough to mill.Fat was extracted from the dried samples as described below; the non-saponifiable residue was stored at about 3 O until rats were available for the biological assays, when it was dissolved for dosing in a suitable weight of arachis oil.Shinjield pastures and hays.The making and sampling of the different hays are described in detail by Murdoch et al. (1959).For convenience relevant information about the hays is summarized in Table 3 B. T h e dry herbages were stored in sealed tins at 3' until rats were available for biological tests and were then extracted and dissolved for dosing as described below. Methods of extractionOriginally the air-dried samples were extracted directly with light petroleum.During the course of the experiments, however, Weits (1953 a ) reported that this method usually did not remove all the vitamin D activity from samples and that more