202 INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [III, II

Phosphorus deficiency.—Naturally occurring deficiencies of mineral elements
have been shown to affect fertility. Of these, possibly the most important is
deficiency of phosphorus since it is of widespread occurrence in natural pastures
throughout the world. It has been shown by Theiler and his associates in South
Africa, by Henry in Australia, and by Eckles, Becker and Palmer and Hart in the
United States, that deficiency of phosphorus results in abortions and sterility.
In observations on 200 native scrub cows, half of which received a supplement of
bone meal, Theiler, Green and Du Toit (34) found that 80 per cent. of the bone-
meal lot calved normally, while only 51 per cent. of the controls calved. Du Toit
and Bisschop (35) report an experiment continued for three years with 109 bone-
meal-fed cows and 20 controls in which the bone-meal-fed group produced 87.3
per cent. of the possible number of calves, while the control group produced only
56.5 per cent. of the possible number. Eckles, Becker and Palmer (36) also found
that feeding a phosphate supplement improved fertility. They attributed the low
fertility associated with phosphorus deficiency to infrequency of ovulation. Hart
(37) finds that, in certain range areas in the States, where the calf crop is low,
the pasture, although quantitatively sufficient, is deficient in phosphorus and pro-
tein and the calcium/phosphorus ratio is high. On such pastures cows become
emaciated and œstrus does not occur. Laboratory experiments on rats, designed
by Hart to throw light on the causation of this sterility, have shown that under-
nutrition stops the normal cycle of ovarian changes, and that a diet low in pro-
protein and phosphorus, or with a high calcium/phosphorus ratio, interrupts the
cycle or greatly lengthens the interval between ovulations. Hart describes
trials in supplementary feeding in which a supplement of cotton-seed cake, rich
in protein and minerals, gave excellent results, 50 per cent. of the cows being
re-bred within a month after calving.

Calcium deficiency.—It is not generally considered that deficiency of calcium
occurs to any great extent under natural conditions. It is, however, known to
occur in some areas, for example, the Falkland Islands and hill pastures in Scot-
land (38). In most cases observations on such areas are complicated by the co-
existence of general under-nutrition. We have, therefore, no data regarding the
effect of calcium deficiency on fertility under natural conditions.

In experiments in which dairy cows were fed greatly restricted rations, con-
fined practically to a single fodder-plant oat, wheat or maize, Hart (39, 40, 41, 42)
and his co-workers showed that addition of calcium was essential to secure repro-
duction. The results were further improved by addition of butter or cod-liver
oil and salt. Hart also records that cows fed on hay and straw grown on acid
soils and containing less than the normal percentage of calcium were unable to
produce normal healthy calves. In an experiment using a ration of low calcium