GEORGE
H.
HART
81
carotene they contain, and expressed in
ternational units of vitamin A.
SYMPTOMS OF VITAMIN A DEFICIENCY
CATTLE
General
The effect of vitamin A deprivation has
been extensively studied in the bovine.
Although a variety of manifestations may
be present the diagnosis, particularly in
ilder forms, may be difficult. Hart, Mead
and Guilbert [1933] found that the time of
manifestation varied in the same herd,
because of differences in the previous food
supply and amount of reserve stored by
e animal. The state of maturity, lacta-
tion, gestation, development, production
and rate of growth all influenced the onset
symptoms. Thus serious symptoms
and fatalities may be present in young
ock while adult animals show no symp-
toms. Newborn calves from dairies on
lfalfa ranches' when taken to be nursed
depleted cows on a 'grain ranch' re-
-ained normal for 6 to 8 weeks. At the
same time the calves of depleted cows on
the same 'grain ranch' were weak and died
1 to 5 days. This would indicate that
newborn calves from the former farms had
reserve sufficient for a period of 6 to 8
weeks. Mead and Regan [1931], in their
earlier work with calves on rations devoid
of roughage, found that symptoms deve-
loped in 1 to 3 months after the animals
were changed from whole milk and grain
to a concentrate mixture low in vitamin A.
Halverson and Sherwood [1930] demon-
strated that cottonseed poisoning of cattle
as in fact caused by vitamin A deficiency.
n one experiment a large percentage of
teers on an exclusive ration of cottonseed
eal and hulls developed symptoms in 88
days. In other experiments dairy heifers
averaging less than 1 year of age were
continued on the ration for 200 days
before the advent of acute symptoms,
Evidence is adduced by Flora et al. [1939]
that animals on deficient rations contain-
ing cottonseed developed symptoms in a
shorter time than when the rations did not
contain cottonseed.
Guilbert and Hart [1934] studied the
time required to deplete non-lactating
cattle which had had ample opportunity
to store vitamin A. Twelve steers 9 to 20
months of age were raised on native green
pasture, irrigated alfalfa, or sudan grass,
with alfalfa and sudan grass hay in the
winter season. The first group of ani-
mals, 4 in number, 12 to 19 months of age,
was killed at the start. Their livers con-
tained from 500 to 830 blue units per g. of
liver tissue. The second group, 6 in num-
ber, was placed on the experimental ration
consisting of dried molasses beet pulp 70,
rolled barley 14, cottonseed meal 15 and
CaCO 3 1 per cent. These animals were
killed in pairs, 63, 121 and 282 days, res-
pectively, after being placed on the ration;
the last pair was in an advanced stage of
vitamin A deficiency. The animals in this
group showed a progressive loss of liver
reserve. The first pair had 250 and 420
blue units (per g. of liver), respectively,
the second, 160 and 50, and the last pair
afforded only a trace of blue colour with
the unsaponifiable matter from 20 g. of
liver. Symptoms did not appear in the
first 4 animals and were manifest after
225 days in the last pair. One after 252
days showed night blindness. The other
animal had a slight nasal discharge on the
241st day and was also night blind on the
252nd day with some evidence of incoordi-
nated movements. Facial paralysis deve-
loped in both animals and in one of them
the left ear drooped. The appetite and
general appearance remained normal. On
the 276th day a mild diarrhoea developed;
nasal discharge and muscular incoordina-
tion became rapidly more marked, the hair
appeared rough, appetite failed, weight
rapidly declined, but no lesions of the
cornea developed. They were slaughtered
on the 282nd day.
No abnormality was found on post
mortem examination and the carcases
passed meat inspection. Both animals had
a dressing percentage of about 65. The
fat was snow white, whereas those killed
at the expiration of 63 and 121 days
showed a creamy yellow fat, and those