THE CHEMICAL COMPOSITION AND VITAMIN A POTENCY OF COW'S
MILK AND BUTTER FAT UNDER INTENSIVE GREEN FEEDING
AND THE CAROTENE METABOLISM OF DAIRY ANIMALS
By B. C. RAY SARKAR and K. C. SEN, Animal Nutrition Section, Imperial Veterinary Research
Institute, Izatnagar
(Received for publication on 4 August 1942)
IN a previous paper [Sen and Ray Sarkar, 1942],
a study was made of the effect of different levels
of carotene ingestion in the form of green feed
on the carotene and vitamin A potency of milk
and butter fat, and it was found that, with the
ingestion of a carotene-rich diet, both the carotene
and vitamin-A contents of butter fat tended to
reach a maximum value. An increase in the
blood plasma carotene and its vitamin A content
was also observed. With an intake of about
869128 I.U. per day, the average vitamin A
potency per pound of butter fat was about 9745
I.U., the carotene portion providing approximate-
ly 27 per cent of the total potency. In view of
the fact that occasionally, pooled milk from the
Institute Hariana herd, which was allowed free
grazing in addition to considerable green rations,
showed a higher vitamin A value than that of
stall-fed animals, it was felt that a further investi-
gation was needed to determine the effect of a
very heavy ingestion of carotene on the vitamin A
output in the milk of the local Hariana animals.
Along with this, the variation, if any, in the che-
mical composition of the milk and the butter fat,
consequent upon this heavy green fodder ingestion,
required study. Accordingly, a detailed experi-
ment was planned and the present paper contains
the results so far obtained.
Dean and Hilditch [1933] studied the factors
which influenced the component fatty acids of
butter and showed that there was a variation in
the iodine and Reichert-Meissl values of the
milk fat of cows when fed on pasture during the
summer or fed indoors during the winter. The
iodine value was higher in the first case but the
Reichert-Meissl value was lower. Das Gupta
[1939] observed an increase in the Reichert-
Wollny and iodine values, associated with a high
carotene content of the butter when the animals
were on abundant green pasture. Doctor et al
[1940] also noticed a rise in the Reichert value of
butter fat on feeding greën grasses, when the caro-
tene and vitamin-A content increased as well.
Makhijani and Banerjee [1938] studied the effect
of feeding different amounts of guinea grass to
cows on the carotene content of ghee and blood
serum. There was no change in the vitamin A
content of ghee in this particular experiment but
from the data on the carotene content of blood
serum, it appears that there was a definite rise
after green fodder ingestion. Bal and Shrivastava
[1940] reported the periodic fluctuation in the
carotene content of cow and buffalo butter fat
due to a variable feeding of green fodder.
This paper deals with the following points :
(a) The change in the chemical composition of
milk and butter fat due to the heavy green fodder
ingestion.
(b) The effect of heavycarotene ingestion through
different grasses, on the carotene and vitamin-A
content of milk fat.
(c) The computation of the carotene balance, and
(d) The change in the blood plasma carotene
and vitamin A content, consequent upon a
change in the carotene intake.
EXPERIMENTAL
The investigation was divided into two parts
In the first part, the effect of a variable ingestion
of berseem and oat grass during the months of
December and January was studied. In the
second part, the result of a moderately heavy
ingestion of dub grass during the monsoon month
of August was investigated. The two sets of
experiments were carried out with different ani-
mals, all of the Hariana breed, under stall feeding
conditions. The animals were milked twice daily,
and free exercise was allowed for one hour both
in the morning and in the afternoon after milking.
The amount of concentrate mixture (wheat bran
40 parts, gram husk 20 parts, groundnut cake
20 parts, rape cake 10 parts and gram chuni 10
parts) was regulated according to the milk yield
and varied from 7.5 lb. to 11.5 lb. daily, but,
in one experiment mentioned later, it had to be
cut out completely for a few days, because of an
ad libitum green fodder feeding. An estimation
of the carotene and vitamin-A in milk and plasma
and in butter fat was carried out, according to the
procedure detailed in the previous paper. The
chemical composition of milk and butter fat was
determined by the methods given by the Asso-
ciation of Official Agricultural Chemists of U. S. A.
[1935]. The Wij's method was used for iodine
number determination. The carotene content of
feeds and faeces was estimated by the usual
method adopted in this laboratory [Seshan and
Sen, 1942],
219