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Vitamin-A Deficiency in the Diet of Farm Animals
Brown Swiss and Jersey cows gave intermediate values [Baumann et al, 1934].
In a comparison between Holstein and Ayrshire butters it was found that
biologically both had the same total vitamin-A potency [Beeson, 1935].
The butter-fats of Guernsey and Holstein breeds were approximately equal
in vitamin-A potency but definitely superior to those of the Ayrshire and
Jersey. The carotene contents under winter conditions were, Ayrshire 1.45
mg. per kg., Holstein 1.95, Jersey 2.05 and Guernsey 3.45 ; under summer
pasture the figures were 4.7, 8.0, 12.1 and 20.5 mg. carotene per kg. of
butter respectively [Sutton and Krauss, 1936]. Another experiment showed
that the carotene and vitamin-A value of the butter of Guernsey, Friesian,
Ayrshire and Shorthorn cows were in descending order [Gillam et al, 1936].
It has been suggested that each breed of cow would have a " ceiling value "
above which it would not be possible to increase the vitamin-A potency of
its milk or butter [Gillam and Heilbron, 1934].
CONSERVATION OF VITAMIN-A POTENCY OF ROUGHAGES
It has already been found that most forage plants in their fresh young
stage yield a sufficiency of vitamin-A to animals fed or grazed on them. If
an animal is, therefore, assured of green feed as a major fraction of its rough-
age, then the vitamin-A problem in cattle ceases to exist. But, however,
desirable it may be, it may not be possible under practical conditions of farm-
ing to provide such feed throughout the year. The problem, thus, reduces
itself to a question of fodder preservation with a view to retain the carotene
content of the plant at the optimum level.
Ensilage is one of the methods of preservation which has been tried in
this connection. In studying the effects of the feed on the carotene content
of butter, it was observed that forty lb. of A. I. V. silage in the feed raised the
yellow colour to a level comparable with that found on best pasture, while
the vitamin-A content was doubled [Gillam and Heilbron, 1932]. Corn
silage was found to be a valuable source of vitamin-A for feeding dairy animals
[Russell et al, 1935]. A. I. V. silage made from grass and clover or young
alfalfa were tested as suitable vitamin-A feeds to dairy cows. It was found that
thirty kg. of the former and fourteen kg. of the latter gave adequate response
[Steensberg, 1936]. Winter milk from cows fed on A. I. V. silage was as
high in vitamin-A potency as that of summer milk on pasture, namely, about
three times that of cows fed on hay, concentrates and roots. The A. I. V
process resulted in good silage which preserved the carotene and vitamin-A
contents of the green plants intact. It may also be pointed out incidentally
that while hay-making destroyed the vitamin-C entirely, in the A. I. V. silage
half of it was preserved [Virtanen, 1935].
Hay-making is another method of fodder preservation which can be
utilised for the preservation of the carotene content of fodder plants. The
factors involved in hay-making are so prejudicial to the retention of carotene
or vitamin-A activity that much attention has been devoted to finding out
the best process of hay-making to suit the vitamin-A requirements of animals