GEORGE
H.
HART
85
EFFECT ON REPRODUCTION
After it became established that vita-
min A was essential for normal reproduc-
tion in mammals, the study of the effects of
s deficiency on reproduction in the bovine
becies was complicated by the widespread
kistence of infectious abortion.
The early work of Hart, McCollum,
teenbock and Humphrey [1911] on the
effect on reproduction of rations restricted
to a single plant, wheat, oats or maize,
oved conclusively that failure of repro-
nction could be of nutritional origin.
Their first experiments led them to suggest
that toxic bodies carried in the rations or
produced in the intestinal tract, and also
oor mineral content of the diet, might
afford a possible explanation. Further
work, published in 1917 after the disco-
very of vitamin A, did not suggest that
the absence of this vitamin was the cause.
In 1920 additional work with the oat plant
was published and again reproductive
failure occurred; this was attributed to low
a. Hart, Steenbock, Humphrey and
Hulce [1924] presented new observations
and fresh interpretations of the previous
work from which they concluded that the
wheat plant was deficient in both vitamin
A and Ca. The addition of these subs-
tances made the wheat plant ration comp-
lete for reproduction, thus making it
unnecessary to continue to assume the
presence of a toxic factor.
Hadley and Hawn [1929] and Hart,
adley and Humphrey [1932] demonstrated
that a good ration did not increase resis-
tance to infectious abortion nor did a poor
ne increase susceptibility. In their ex-
---ience lack of vitamin A was an impor-
tant cause of failure of reproduction.
Incidentally they confirmed the observa-
tions of Golding, Soames and Zilva [1926]
that cod liver oil given to cows on a high
plane of nutrition was responsible for
reducing the butterfat by more than 20
per cent.
Meigs and Converse [1932] reported
affects on reproduction in dairy cows of
rations containing low grade roughage.
After fairly long periods on grain and
U.S. No. 3 timothy hay the animals gave
birth to premature dead or weak and blind
calves. When a better grade of timothy
hay was given the proportion of normal
claves was larger and, when the roughage
consisted of U.S. No. 1 alfalfa hay repro-
duction was quite satisfactory.
Hart and Guilbert [1933] studied vitamin
A deficiency in a severe natural outbreak
in a herd of 250 head of which 100 died.
Reproductive failure was complete in 25
to 30 cows calving at the height of the
deficiency; all the calves were born weak,
had severe diarrhoea and died in 1 to 5
days. Less severe manifestations were
reported by Hart, Guilbert and Goss[1932]
under natural range conditions during
prolonged dry seasons.
When expulsion of weak or dead offspr-
ing occurs, a differential diagnosis can be
made between this condition and that of
infectious abortion, if conditions permit
agglutination tests with Brucella abortus
antigen to be made. The Carr and Price
colorimetric test can be applied to liver
samples of the foetuses and, if no colour is
obtained, vitamin A deficiency is to be
considered. Both conditions may be
involved, as indicated by the experiments
reported by Haring and Traum[1937].
Infectious abortion attacks the cells of the
maternal and foctal placenta. The same
cells are affected in vitamin A deficiency.
Mason [1935] has shown that in vitamin A
deficiency foetal death is secondary to
marked placental injury, whereas vitamin
E deficiency affects the foetal tissue
primarily.
Diarrhoea in the newborn due to vita-
min A deficiency may be confused with
white scours. The history of the cases
and analysis of liver tissue will help in
diagnosis. If due to the former it will be
promptly cured with vitamin A therapy.
Severe losses from white scours occur
when intake of vitamin A is ample and its
use as a therapeutic agent under these
conditions is unavailing. A recent report
on this subject has been made by Stewart