82
Vitamin A requirements of Form mamm als
killed at the beginning of the experiment
showed a still deeper colour. Carotene
appears to be withdrawn from the adipose
tissue during vitamin A deprivation with-
out coincident reduction of the reserve of
fat. The last pair showed a uniform daily
increase of 1 and 1.3 lb. up to a few days
before slaughter. This result is in har-
mony with that of experiments on swine
by Lund [1938] in which vitamin A defi-
ciency did not affect digestion, protein
and mineral metabolism or the utilisation
of energy, but the appetite was gradually
lowered.
The third group, containing 2 animals,
received, in addition to the concentrate
mixture, 1 lb. daily of high quality field
cured alfalfa hay. When slaughtered on
the 127th day their livers had only 50 and
80 blue units, respectively, per g. of liver
tissue, indicating that the limited intake of
alfalfa had had little effect on the main-
tenance of their reserves.
In another experiment a heifer on a
diet low in protein, phosphorus and vita-
min A passed through a gestation and
lactation but her milk flow was so meagre
that her underdeveloped calf gained only
25 lb. in 5 months. Nevertheless the
mother, after 14 months on the diet,
showed no symptoms of vitamin A defi-
ciency. Newborn calves were shown to
have low reserves, indicating that the
pregnant mother on high intake is unable
to supply vitamin A to the foetus much
faster than it is utilised. Dann [1932]
showed this to be the case in rats and
rabbits. Thus the foetus will suffer first
when borderline deficiency is reached.
In agreement with Drummond, Coward
and Watson [1921] and others, colostrum
was found to be relatively rich in
vitamin A.
Eye. Bechdel, Honeywell and Dutcher
[1928] reported blindness in 1 of 5 animals
on a ration deficient in vitamin A.Eye lesions
were reported in calves by Halverson and
Sherwood [1930] in their studies on cotton-
seed poisoning. Meiga and Converse [1932]
also reported the birth of blind calves in
cows on low grade roughages. Mead and
Regan [1931] demonstrated typical xerop
thalmia in some of their calves raised of
diets without roughage. Sanchez [1933]
and also Schieblich [1934] described
similar condition in Spain. Two hundred
milk cows taken to Seville from Switzer-
land gave birth to calves 80 per cent
which were blind without visible ey
lesions. Native cows also gave birth
blind calves and the incidence decreased
after green food was given.
In the severe outbreak reported by
Hart and Guilbert [1933] the eye lesions
in the animals from a few weeks to one
year of age varied from profuse lachry
mation and slight clouding of the corn
to extensive keratitis, ulceration of the
cornea, loss of the aqueous humour, le
opacity and shrinking of the eyeball wi
complete and permanent blindness. Clou
ing and ulceration of the cornea was also
present in the steers from 1 to 2 years of
age. Practically all of the adult cow
showed night blindness without cornea
lesions.
Night blindness from vitamin A defi
cieney is believed to result from an inad
quate rate of regeneration of visual purple
The nature of the defect has been elucid
ted by Wald [1934], and has recently been
discussed and the pertinent literáture
reviewed by Tansley [1939]. Cows the
are deficient only during the early month
of pregnancy may give birth to permanent
ly blind, but otherwise normal, calves. I
young animals the amaurosis, once deve
loped, is nearly always permanent, irrespec
tive of the amount of vitamin A subsequent
ly ingested. There has been some differen
ce of opinion as to the cause of this form
of blindness because it has occurred under
conditions in which vitamin A deficienes
was not suspected, and other possible
causes have been suggested. The case
reported by Crocker [1919] and considered
to be the result of insidious rachitis were
probably due to lack of vitamin A. D.
Schweinitz [1931], and De Schweinitz and
De Long[1934] described a similar condi
tion under the name of papilloedema on
choked disc and suggested that the defec