226
Vitamin A Potency of Cow's Milk and Butter Fat
TABLE XII
Recovery of carotene and vitamin A in the butter fat of cows fed on dub grass
Animal No.
75
77
78
Average
Average
daily
carotene
intake
I.U.
1752960
1752960
1962120
1822680
Total recovery per day
Carotene
I.U
1434.9
2053.4
1281.5
1589.9
Vitamin A
I.U.
4192.7
5545.3
4238.9
4659.0
Total
I.U.
5627.6
7598.7
5520.4
6248.9
Per cent recovery per day
Carotene
0.08
0.12
0.07
0.09
Vitamin A
0.24
0.32
0.22
0.26
Total
0.32
0.44
0.29
0.34
TABLE XIII
Carotene balance on dub grass feeding
Animal
No.
75
77
78
Average
Average
daily
carotene
intake
mg.
1056
1056
1182
1098
Average daily output (mg.)
In faeces
557.5
668.3
618.8
614.9
In milk
3.39
4.58
3.33
3.76
Total
560.89
672.88
622.13
618.66
Balance
mg.
+495.11
+383.12
+ 559.87
+ 479.34
Per cent
excretion in
faeces
52.8
63.3
52.4
56.0
It may thus be seen that an increase in the ingestion
of carotene from approximately 24000 I.U. to
300,00,00 I.U. raised the total potency of butter
from about 6000 I.U. to approximately 10,000—
11,000 I.U. per pound, both in the case of berseem
and in the oat grass feeding. In other words,
the total vitamin A potency increased by 93 per
cent, the carotene potency increased by about
267 per cent and the vitamin A by about 69 per
cent (average of the figures of berseem and oat
grass feeding in period III). There was no appre-
ciable difference in the potencies when the inges-
tion of 60 lb. was replaced by 120 lb. of green
grasses. Therefore, the maximum potency ap-
pears to be independent of the amount of green
fodder ingestion, after a minimum quantity has
been fed.
It is clear from the data on recovery (Tables VI
and VII) that on a lower level of carotene intake,
the total recovery of vitamin A in milk was on the
average 20.95 per cent of which vitamin A con-
tributed 18.2 per cent. At this level of intake,
the animals were in negative carotene balance
(Tables VIII and IX). This high percentage
of vitamin A secretion took place probably from
the body reserve. When the feeding was 60 lb.
and 120 lb. of grasses, the respective total recover-
ies were, however, 0.41 and 0.26 per cent.
A consideration of such an enormous wastage
raised the interesting question of studying the fate
of ingested carotene by metabolism experiments.
In Tables VIII and IX, carotene balance data on
the berseem and oat grass feeding are given.
In computing the balance, the vitamin A secre-
tion in milk has been expressed in terms of absolute
units of carotene. On a lower level of carotene
intake (14.3 mg.), the carotene in milk formed
13 per cent of the faecal carotene (average of four
animals), while the latter was about 160 per cent
of the total intake, the total balance being thus
appreciably affected here by milk carotene secre-
tion. On increasing the level, however, to 1400
mg. of carotene, the faecal excretion was 69 per
cent of the intake, and with a still further increase
(1800 mg.), the positive balance is increased, but
the percentage excretion in faeces remained more
or less the same. Under such heavy ingestions,
the milk carotene was only about 0.05 per cent
of the faecal carotene (average of groups 1 and 2
in periods II and III). The position is thus quite
different with higher level of carotene ingestion,
when the carotene balance is but slightly affected
by milk carotene.
If the remaining 31 per cent of the total intake
be presumed to be absorbed, then the total reco-
very in milk on the basis of the absorbed amount
does not exceed 1.0 per cent.
The effects of the different levels of carotene
ingestion on the carotene and vitamin A content
of the blood plasma are shown in Table X. A
heavy carotene intake raised the level of both
carotene and vitamin A considerably. The greater