Factors Affecting the Antirachitic Activity of Alfalfa and Its Ability to Prevent Rickets in Young Calves

Green plants have been shown to be low in antirachitic activity and it has been assumed that artificially dried roughages contain little or ,no vitamin D. The antirachitie activity of artificially dehydrated alfalfa was found to be nil or too small to measure (33,34,35) and to be increased by exposure to sunshine after the green alfalfa was GUt for hay (3,33,34,35,39).In fact, an inverse relation between the carotene and vitamin D content of alfalfa has been demonstratcd (30,34,39).There also is evidence that some roughages possess antirachitic activity without being exposed to solar radiation while drying (2, 5, ]9, 23, 25, 29, 38, 39).Several investigators found no direct relation between the vitamin D content of the hay crop and the amo~tnt of sunshine it received during the curing process (19,25,29,39).I [odgson and Knott (19) found that g'reen pasture herbage had definite calcifying activity for rats, the amount being equal to that found in the same material cured in the sun for 15 hr.Voltz and Kirseh (38) found antirachitic activity in English ryegrass, even when it was grown in total darkness on garden soil or on a nutrient medium.IIowever, IIess and Weinstock (17) found no activity in the young wheat plant grown in darkness, but when grown in light and artificially irradiated while growing, it was found to have definite antirachitic activity.They also found no antirachitic activity in lettuce until after it was cut and artificially irradiated.Mellanby and Killiek (23) found some antirachitic activity in summer-grown grass, dandelion leaves, and carrot and turnip greens, but none in cabbage.Green summer-grown spinach was reported to have slight antirachitic activity for the rat but no activity was found in spinach grown under tinted glass or in that grown during the fall, winter or spring months (5).Recently, three different investigators (25,29,30,42) presented data showing that the vitamin D content of the hay crop was not always correlated with the amount of sunshine it received during the curing process.The evidence indicates, as has been mentioned previously by this laboratory (25) and by others (40), that factors other than the amount of sunshine the roughage receives during curing may influence its final antirachitic a~etivity.Since these other factors have not been investigated heretofore, one purpose of the experiments reported in this paper was to investigate their nature.It is well known that the young ruminant requires some form of vitamin D for proper growth and bone formation.It has been well established that both sunshine (1, 7,11, 13,15,31,32,40) and the usual field-cured roughages (3,4,16,21,26,31,40,41) are able to furnish the antirachitic factor to the young ruminant.Under usual conditions, these sources have supplied sufficient