STUDY ON THE VITAMIN A ACTIVITY OF CAROTENE IN GREEN FODDER
By B. C. ROY SARKAR and K. C. SEN, Imperial Veterinary Research Institute, Izatnagar, and Imperial
Dairy Research Institute, Bangalore, India
(Reprinted from Journal of Agricultural Science, Vol. 36, Part 2, April 1946)
I N some recent papers, Seshan and Sen (1942 a.b.c.d) described a modified technique for extracting
carotene from different feeding stuffs and utilized it for the study of carotene in plants including
some balance experiments with ruminants. It was pointed out by the authors that the term carotene
was used in the ordinary sense denoting the epiphasic pigment, and no chromatographic study was
made of the time. As such, the carotene figures for materials like old stored hay straw, silage and
cattle faeces were liable to revision because of the production of non-carotene pigments not removable
by phase separation with 90 per cent methyl alcohol used in the method, but it was felt that no sub-
stantial error was likely to be caused in the case of green fodders. It was, however, decided to check
up the method by simultaneously carrying out a biological and chromatographic assay of the carotene
contained in the feeding stuffs. The results obtained are being presented below, and based on these,
the Seshan-Sen method of extraction of carotene has been combined with chromatographic adsorption
for the routine analysis of vitamin A-active carotene in feeding stuffs. While these data were being
written up, Austin and Shipton [1944] published a critical examination of the methods of determin-
ing carotene and came to the conclusion that, of the variety of methods designed for the extraction
of carotene, that proposed by Seshen and Sen was the most satisfactory, being decidedly more efficient
and more widely applicable than the process recommended by Peterson, Hughes and Freeman [1937].
Austin and Shipton have suggested the use of 'heavy' magnesia for the chromatographic separation
of non-carotene pigments in conjunction with slightly modified Seshan-Sen method of extraction.
Although a fair amount of work has been done by different investigators on the determination of
carotene for evaluating theoretically the vitamin A potency of stock feeds, there are comparatively
few data on the relation between the carotene content and the vitamin A potency of those materials
as measured biologically. Woods, Shaw, Atkeson and Johnson (1932), Woods, Atkeson, Wellhonsen
and Johnson (1935a), Woods, Atkeson, Shaw, Slater and Johnson (1935b), Woods, Atkeson, Slater,
Arndt, and Johnson (1935c) and Archibald, Bennett and Pitchie (1943) determined the biological
potency of certain grasses, but their carotene content was not simultaneously estimated. The
work of Taylore, Russell and Bender (1939) on the carotene content and vitamin A potency of different
types of silage, and that of Hodgson, Murer and Knott [1939] on green, dehydrated and sun cured
pea vines and pea vine silage, etc., may also be mentioned, although some of the results obtained
are of questionable value. In the case of green vegetables and other plant foods, some work by
different workers is on record. Felice and Fellers [1937] obtained a factor 1.7 for converting the
carotene values of fresh, frozen, canned and dehydrated samples of spinach into the vitamin A
potency. Gorter and Spruyt (1939) reported that some foodstuffs were found to contain less pro-
vitamin A by the rat test than that obtained by chemical analysis. Stimson, Tressler and Maynard
[1939] found the ratio of vitamin A potency to carotene to be 1.5 in the case of fresh and frosted
peas. Smith and Otis (1941) pointed out the ralative inefficiency of yellow vegetables, notably
carrot when compared with green sources. Greaves [1942] observed that carotene of vegetables
seems to be less effective biologically than vitamin A and the vitamin A activity per unit of carotene
was much greater in spinach, water cress and alfalfa than in carrots. Zimmerman, Tressler and
Maynard [1940, 1941] found that much of the pigment of Golden Cross Bantam Sweet Corn was not
carotene, while the vitamin A activity of asparagus was solely due to ß-carotene and that of green
lima bean due to two thirds ß-carotene one-third α-carotene.
To explain the discrepancy between the chemically determined carotene and its biological
activity and the superiority of carotene from one type of material over that from another, it is desir
able to know whether carotene estimated chemically is biologically as active as ß-carotene, and if
not, to determine its purity; secondly, how far the ingested carotene is absorbed and utilized in
the system. For the elucidation of these points, the following series of experiments were
conducted.
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