142
Study on the Vitamin A Activity of Carotene in Green Fodder
TABLE II
Percentage of true carotene in apparent carotene
Source
Standard carotene
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Barley plant . . . . . . . . . . . . . .
Oat plant
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Berseem
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.
.
Lucerne . . . . . . . . . . . . . . .
Elephant grass
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Dub grass
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Kolluiattai grass
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.
Spinach
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Hay
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Straw
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Silage
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Faeces of bullocks :
On prolonged straw ration
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On moderate green ration
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On heavy green ration
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By
chromato-
graphy of
apparent
carotene
98.95
95.9
98.0
94.2
98.3
86.7
93.0
92.0
97.1
..
..
..
..
..
..
By
chromato-
graphy of
total
carotenoids
..
97.8
96.7
95.9
94.0
85.1
92.9
93.6
99.9
36.5
0.0
32.5
0.0
78.8
80.0
It will be observed from the results given in Table II that the green fodders contain only a very
small amount of impurity, and this must be the reason why the chemical estimation of carotene of
green fodders gives a fairly close picture of its biological activity as tested against standard carotene.
It will also be noticed that on heavy green fodder ingestion, the true carotene content of faeces from
bullocks is as high as 80 per cent of the apparent carotene excreted. This means that it would be diffi-
cult to differentiate between the chemically estimated carotene in faeces of animals fed a heavy green
ration and that assayed biologically, which has actually proved to be the case. In other words the
whole of the excreted carotene appears to be biologically active because of the margin of error inherent
in biological assay. On the other hand when cattle are kept on mainly dry roughage, the faeces
contain much less of true carotene, as shown by chromatographic and biological assay. The observed
negative balance of carotene in the case of ruminants on carotene-low rations, as described in a pre-
vious paper [Seshan and Sen, 1942 d], thus loses much of its significance. It may be mentioned
that according to Russell, Taylor, Walker and Polskin [1942] no resorption of body carotene into
the alimentary canal takes place in the case of hens. An alkali and alcohol digestion of feeding
stuffs should, therefore, be followed by chromatographie adsorption to give a true idea of the bio-
active carotene present.
(3) Absorption of fodder carotene in avitaminotic rats
Although the chemical, chromatographic and biological methods of a assaying carotene in green
fodders have given similar results, it was of interest to determine if the activity manifested in the
biological assay was really due to the absorption of the total amount of carotene ingested and to what
extent the amount absorbed was converted into vitamin A in the system. It has been reported
recently by Ramasarma and Hakim [1942] that 10-15 per cent of carotene fed to rats at 1-2 µg. level
of dosage is excreted viâ the faeces. It is also known that vitamin A is generally utilized better
than carotene [Booher and Callison, 1939; Booher, Callison and Hewston, 1939; Guilbert, Howelt
and Hart, 1940; Smith and Otis, 1941 ; Treichler, Kemmerer and Fraps; 1942; Guggenheim,
1944]. To obtain an idea of the fate of the ingested carotene, some absorption studies were carried
out.
From a sufficiently large quantity of faeces of the rats under various test groups and the positive
controls, carotene was estimated separately according to the method of Seshan and Sen, with an
additional step of cooling down the final extract to 0°C, before dehydration over anhydrous sodium