MINERAL REQUIREMENTS OF CATTLE IN NORTH-EAST INDIA
185
In the absence of direct evidence it is difficult to assign any definite reason for
this, but if the figures under rice straw feeding are carefully studied it is noted
that rice straw involves a very large ingestion (about 70 to 80 grms. per 500-lb.
live-weight) of potash. This is generally much in excess as compared to what
is ingested through many of the other feeds. Orr [1925] considers that " the
ratio of sodium to potassium affects the assimilation of both calcium and phos-
phorus ". Godden [1928] says that his work in conjunction with Richards and
Husband has shown that an excess of potassium in the ration while temporarily
depleting the sodium has its main effect " on the nitrogen, calcium and phos-
phorus balances ; a high ratio of K 2 O : Na 2 O tends to lower the assimilation
of these constituents, whereas when the sodium is in excess the assimilation
is raised " and he remarks that this " may be the explanation of the beneficient
results of feeding sodium chloride to stock ". Remy and Müller [1931] have
found in rats that a diet with a high content of potassium results in rachitic symp-
toms and they ascribe it not to high potassium intake but to the consequent
diminution of the Ca : K ratio. Armsby states [1917] " that fodders that cause
malnutrition of the bones resulting in the disease known as rickets (Rachitis)
usually show a misproportion of potassium to sodium " and he cites figures from
Zuntz . [1917] of such fodders (hay) causing the disease.
It need hardly be stated that very little work has been done on the aspects
of calcification under cereal straw feeding. Much work has, however, been done
with cereal diets and various investigators have noted a deleterious effect upon
the calcification of bones and teeth in dogs and rats when fed with cereal diets.
E. Mellanby [1926] proposed the idea that cereals contain some distinct anti-
calcifying substance which he provisionally called a toxamine. Mellanby
[1928, 1929] noticed that those cereals which frequently contained the most Ca
and P had the worst effect on teeth and that Ca/P ratio was not found responsible.
Holst [1927] reported a ricket-producing factor from oats which could be extracted
with 0.5 per cent HCI and Mirvish [1929, 1930] reported that when a dilute HCI
extract of oats was injected into animals it produced a marked fall in blood
calcium. Fine [1930] ascribed the difference in the calcifying properties to varia-
tions in the vitamin D content. Lowe and Steenbuck [1936] found that the in-
organic phosphorus content of variously treated samples of maize bore a direct
relation to the anti-rachitic effectiveness of the ration and an inverse relation
to the phytin content, and the hydrolysis of phytin by HCI improved it to the
extent of hydrolysis.
It is very difficult to say how far similar probabilities are associated with
the feeding of cereal straw. But there can be no doubt that the comparatively
larger requirement of lime under rice straw feeding must be due to a poorer eco-
nomy. It has been suggested by Hunter and his co-workers [cited by Godden,
* Zuntz. 1912 Jahrb. Dent. Landw. Gessell, 577, quoted by Armsby (21), 342.