58
Vitamin-A and Carotene Content of Cow's Milk
carotene. They found colostrum to be 35
times richer in vitamin A and 65 times
richer in carotene than the later milk.
From this it appeared worthwhile to study
the vitamin content of milk at different
periods or stages during one complete
lactation in the Sahiwal breed of
cows.
EXPERIMENTAL
Five Sahiwal cows weighing about 800
lb. each, in their fourth lactation, were
employed for this purpose. This experi-
ment was started about two months after
they had calved and so colosturm could
not be included in this study. During the
early part of the experiment, i.e. April and
May 1942, these cows were on green
berseem, and then from June to November
when the experiment ended with the end
of the lactation, they were on green maize,
and these fodders were fed ad libitum, in
addition to a quantity of the concentrate
mixture of bran and cotton seed. A com-
posite sample of morning and evening milk
was taken daily for fat determination and
the weekly estimation of vitamins.
The estimation of carotene and vitamin
A in milk was carried out according to the
method of Willstaedt and With [1938] in
which 100 c.c. of well-shaken milk is mixed
with one tenth of its volume of 60 per cent
KOH solution. The flask is filled with
nitrogen, stoppered, and vigorously shaken,
and kept aside for 48 hours with occasional
shaking. After this cold saponification,
20 c.c. of alcohol is added, and the whole
extracted with peroxide-free ethyl ether,
extract washed with water, dried over
anhydrous sodium sulphate, and the ether
evaporated in an atmosphere of nitrogen.
The residue is taken up in chloroform for
vitamin A or in petroleum ether for
carotene, and the colour compared in
Lovibond Tintometer for blue and yellow
values.
The data obtained are given in Table I.
The first two columns show intake of green
fodder (average of the previous seven
days) and carotene contained in it. Columns
3,4 and 5 give the total output of butter in
grammes, carotene and vitamin A in milk
grammes respectively, for each of the find
cows. Now, turning to the column fo
green fodder intake by each of the cow
we find that, as these were allowed a
much as they would eat, they consume
between 60 and 100 lb. of berseem daily
(upto 23-5-44), and later on when maiz
was the only green roughage, the average
daily consumption varied considerable
with each cow going up to a maximum o
110 lb.
The amount of carotene intake during
the berseem period varied naturally with
the amount of feed ingested and was bet
ween 1520 mg. and 4950 mg. per day
During the latter period (maize period
the intake decreased considerably due
to the fact that maize is not so rich it
carotene as berseem, although the consump
tion of the former was more or less the
same.
The output of carotene in milk was
about 2 to 4 mg. daily, and this remained
fairly constant for a considerable time
practically throughout the period of lact
ation except in cows No. 4 and 5 where i
fell to a figure round about 1 mg. during
the latter part of the lactation.
The output of vitamin A, calculated
from the blue units into milligrams accor
ding to the formula given by Bartlett and
co-workers [1938] has shown a great con
stancy, although there was a considerable
fall in the daily milk yield, thus indicating
increase in vitamin A towards the end of
the lactation.
The vitamin secreted in milk forms a
very small percentage of that ingested
even in the case of cows which are provided
with enough of green roughages. This
shows that, whereas feeds which are defici
ent in carotene will force the cow to
deplete its reserves of vitamin A and
ultimately lead to poorer milk, it is no
possible to enrich it beyond a certain limit
by feeding carotene-rich feeds. It is inter
esting to observe that each of the cows has
yielded during the entire lactation about as
much vitamin A as is equivalent to its one