84
Vitamine
A Requirements of Farm Mammals
liable to be low in vitamin A. Particular-
ly is this the case with army horses
to which pasturage is not available.
Meadows [1919] was undoubtedly describ-
ing this condition as occurring in horses
and camels in Persia during the Great
War and rendering them useless and
dangerous for night operations.
Guilbert, Howell and Hart [1940] have
determined minimum vitamin A and
carotene requirements of some mammals,
including the horse. Night blindness
developed on the rations commonly used.
The necessity for two standards for
expressing requirements, one for vitamin
A and one for carotene, was pointed out.
PIGS
In their early experiments Hart and
McCollum [1914] showed that when wheat
kernel was the only food supplied, pigs
developed dragging of the hind quarters
and general paralysis, with a peculiar
deflection of the head. This did not occur
when milk or egg yolk was added to the
diet. Histopathological studies of the
tissues of affected swine were reported
two years later by Hart, Miller and
McCollum [1916]. Marked alterations
were found in the motor cells of the spinal
cord. At the time, these were credited to
the inherent toxicity of the wheat kernel
but the possibility was raised of the
limited vitamin A in the diet being res-
ponsible. The paralysis was later shown
by Hughes, Lienhardt and Aubel [1929]
to be caused by nerve degenerations in
portions of the spinal cord, optic, sciatic
and femoral nerves of affected swine.
Hale [1933] reported that a gilt whose
diet was deficient in vitamin A farrowed
11 pigs without eyeballs. Elder [1935]
described cases in which incoordination
occurred under natural conditions with
a stringhalt like gait and posterior para-
lysis. This incoordination in some cases
caused lateral spinal curvature with a
swaying gait and gave the impression that
the hind quarters could not track the fore
quarters but followed off to one side.
Swine paralysis due to vitamin A deficien-
cy was also reported by Dunlop [193
on rations which had been recommended
for general use in England.
In feeding experiments with 0.5 to
per cent commercial cod liver oil given
conjunction with a meal mixture common
ly used in pig feeding practice, Foot et
[1939] found that pigs made good p
gress while controls on the meal mixture
alone failed to thrive. The symptom
shown by pigs receiving no cod liver
included loss of appetite, cessation
growth, impairment of vision in daylight
abnormal gait, convulsive fits and nervo
collapse. Pneumonia or inflammation
the intestines or both occurred in all of
pigs that died during fattening.
SHEEP
Sheep on a diet deficient in vitamin
suffer from night blindness and in some
cases have permanent defective vision
semidarkness, irrespective of subsequent
vitamin A intake or storage. Such ani
mals cannot be used for the study of the
minimum requirements of vitamin A
means of the night blindness test.
Aged ewes, without the drain of repro
duction or lactation, are able to remain
a long time on rations deficient in vitamin.
A without showing symptoms. In 4 su
animals at this station, 22 months elapsed
before night blindness was manifeste
They were killed in cachexia after 27 to
months. As in cattle, vitamin A was with
drawn from stores more rapidly during
the first year than subsequently. Onset
symptoms following the development
night blindness was gradual. They we
anorexia, loss of condition and muscul
weakness. In the final stages 2 of the ani
mals had partially clouded corneas b
sight in daylight was never seriously in
paired. Pneumonia, enteritis and pare
chymatous lesions in the kidney were the
outstanding post mortem findings.
Efforts have been made to trace t
etiology of urinary calculi to vitamin
deficiency but so far without definite pro
Calculi are more common in sheep than
other farm species.