The Comparative Value of a Carotene Concentrate , a L F a L F a Meal , and a Fish Liver Oil in M

I T HAS been widely reported in the literature that carotene from different sources varies in its biological value (Ward, i94o; Fraps and Meinke, Rubin and Bird, t94i; Smith and Otis, i94i; Jones et al. I944). Since much of this work has been done with cattle, poultry, and small laboratory animals it has little direct application to sheep nutrition. If the efficiency of utilization of carotene and other vitamin A active substances by sheep is related to the source of these materials, it should become apparent in a comparison between such widely different sources as alfalfa meal, a natural source of carotene, a carotene concentrate prepared from carrots, and fish liver oil which supplies vitamin A per se. During the course of several experiments, designed to study factors which might influence the concentration of vitamins A and C in the blood plasma of lambs, it was possible to collect data on the storage of vitamin A in the livers of lambs which had received carotene from different sources and vitamin A from fish liver oil. The results of Hauge et al. (I944) indicate that dairy cows can utilize caro. tene from alfalfa hay as well as isolated carotene. King and co-workers (r94o) had previously reported however, that the carotene of alfalfa is more readily available to the bovine than crystalline carotene given in oil. Rubin and Bird (194i) observed that a group of chicks fed alfalfa meal showed .consistently larger stores of vitamin A than did other groups of chicks fed either crystalline carotene or vitamin A. Guggenheim (i944) concluded from his work with rats that the utilization of carotene from various plant sources, or of carotene dissolved in different oils, varied according to the vitamin E content of these materials. The investigations of Davies and Moore 0934) and of Gray, Hickman, and Brown (I94o) indicate that vitamin A per se is utilized much more efficiently by the rat than carotene. Also Hilton and associates (i944) found that the carotene of dehydrated alfalfa hay was only about one.third as