180
Vitamin-A Potency of Cow's Milk
nor the total vitamin-A potency of butter could be further increased. The
total vitamin-A potency determined spectroscopically by Baumannn and
Steenbock and by Atkeson et al., was 14,000 and 13,000 International Units
per pound of butter respectively. Fraps and his co-workers [1937] obtained,
by biological assay, a total potency of about 17,000 Sherman-Munsel units
and Wilbur, Hilton and Hauge [1940] found a value of about 14,900 Sherman-
Munsel units per pound of butter respectively, a Sherman-Munsel unit being
roughly equivalent to 1.4 International Units. All these results appear to
show that the amount of vitamin-A production in butter cannot exceed a
certain limit. As no comparable work of this type has been carried out on
the milch breeds of India, it was thought desirable to carry out some inves-
tigations along this line. Attempts have been made to determine the carotene
and vitamin-A production in the milk of the well known Hariana breed of
dairy cattle under controlled conditions with two different levels of carotene
intake. Incidentally, the effect of carotene ingestion on the carotene and
vitamin-A contents of the blood plasma of cows was also studied.
EXPERIMENTAL
Seven Hariana cows were obtained from the local dairy and were divided
into two groups. The first group consisted of four cows, Nos. 46, 123, 145
and 180. These animals were stall-fed and received the regular herd ration
of concentrate (wheat bran 40 parts, gram husk 20 parts, ground-nut cake
20 parts, rape cake 10 parts and gram chuni 10 parts), 25 lb. of Napier
grass per head and hay for a period of two months. The Napier grass was
poor in carotene, being at a late stage of growth, and this diet represented,
therefore, a low carotene ration. At the end of this period, milk samples
were collected for carotene and vitamin-A estimations, after which the
daily quota of Napier grass was replaced by 10 lb. of berseem. After
an interval of ten days, fresh samples of milk were collected for analysis. The
average milk yields of the cows were 4.8 lb., 9.9 lb., 12.6 lb. and 6.6 lb.,
the stage of lactation being seven, two, two and six months respectively.
The second group of animals consisted of three cows, Nos. 42, 83 and 84.
They were kept in the dairy, allowed free movement and received a ration
containing the above daily mixture with hay. The main source of carotene
for these animals was 28 lb. of berseem daily in addition to a rather
negligible amount available by grazing. After 15 days on this diet, milk
samples were obtained for analysis and then the berseem ration was replaced
by 18 lb. of oat hay daily for another 19 days. This constituted the
carotene-poor ration and, at the end of this period of feeding, milk samples
were again analysed. The average milk yield was 11.75 lb., 15 lb. and 18 lb.
respectively. Animal No. 42 was in the third month and the other two in
their second month of lactation.
As the dairy animals are milked twice daily, in the morning and in the
evening, these samples were examined separately. This gave interesting
information in regard to the carotene and vitamin-A secretion in the morning
and evening milk respectively. A mixed sample representing the total daily
milk yield was also separately analysed. The figures obtained in this analysis