Effect of Raw Soybeans and of Soybean Oil on Plasma Carotene and on Vitamin A as Measured by Activated Glycerol Dichlorohydrin

Summary Feeding raw soybeans in the amount of 9lb. daily to lactating cows caused marked differences in their blood plasma concentration of carotene from that of cows fed a control ration containing no soybean products. During the first 4 weeks the differences increased rapidly, but by 7–9 weeks they seemed to level off at about 250 γ carotene per 100ml. of blood plasma. The reversal in blood plasma concentrations of carotene that took place after a switch-over of rations was made between the cows receiving the control and the raw soybean rations indicates that the causative factor was the feed rather than the individuality of the cows. The feeding of expeller process soybean oil to lactating cows caused differences in their blood plasma concentrations that were intermediate with the concentrations found in the blood plasma of cows fed a control ration containing no soybeans or soybean products and cows fed raw soybeans. The oil apparently depressed the carotene concentrations but not to the extent of the raw soybeans. The differences that occurred in the blood plasma vitamin A concentrations among the cows fed the control, raw soybean and soybean oil rations were small and showed no particular trends. Activated glycerol dichlorohydrin, a new reagent for the determination of vitamin A, proved to be satisfactory for this determination in bovine blood.