250     Carotene and Vitamin-A Contents of butter-fat in cows

During recent years, attempts are being made in India to improve the quality
of ghee or clarified butter-fats which undergo marked seasonal variations parti-
cularly during the autumn and the winter seasons. Thus it is stated that the
best ghee is produced during the winter (from November to early part of March)
and that ghee produced during the monsoon (July to October) is of definitely
inferior quality [Wright, 1937]. It is in the quality of the ghee and not the
quantity that the real improvement of it lies. In this paper, the changes due
to seasonal variations and the effects of feeding cows with different mixtures
of grass and straw and red palm oil on the carotene and vitamin-A contents
of butter-fat have been studied. The Reichert values and Iodine number of
butter-fats are two important characteristics of butter-fats which determine
their quality. It was, therefore, thought advisable to determine these two
values also along with the carotene and vitamin-A contents of butter-fats.

                                I—EXPERIMENTAL

Effect of feeding cows with varying mixtures of grass and straw on the
various characteristics of butter-fats. For this purpose, two healthy cows were
used. They were of the same breed (the common humped domestic cattle of
Bengal), almost of the same age (four years), same period of lactation (three
months). Their body-weights were approximately 500 lb. and milk-yield
about 4 lb. per day (morning and evening). During the experimental period,
which lasted for two months, the animals were kept in a stall. The stall
arrangements and metabolic procedures were broadly similar to what are ordi-
narily used in such experiments.

The feeding experiment was divided into four periods.

Period I.—(2 weeks) Basal diet consisting of a mixture of grass and straw
in the proportion 1 : 1 by weight.

Period II.—(3 weeks) only grass as the roughage in the case of cow D₂
and only straw in the. case of cow D₁.

Period III.—(one week) same as period I.

Period IV.—(2 weeks) only grass in the case of cow D₁ and straw-chops in
the case of cow D₂. The details are given in the following scheme :—