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THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VII, III
It need hardly be stated that sodium and chlorine assume their importance
both from their indispensable nature in the system as well as from their instinc-
tive demand as salt by all animals including human beings. Wild herbivorous
animals have been known to travel great distances in the search for salt licks to
satisfy this craving. The question now arises as to what should be the minimum
amount which should be fed to the cattle specially in the form of common salt—
Kellner [1915] prescribes the daily need of average cow at ¾ to 1½ ounce of salt.
This works out at 11.3 to 22.6 grms. Na 2 O (i.e., 5.6 to 11 3 grms. per 500-lb.
live-weight) and 12.93 to 25.85 grms. of chlorine (i.e., 6.47 to 12.94 grms. of
chlorine per 500-lb.). He has further stated that in the case of difficultly digesti-
ble materials, the quantity may be increased to 2½ ounce (equivalent to 37.66 grms.
soda and 48.08 chlorine or 18.83 grms. soda and 21.54 grms. chlorine per 500-lb.)
but he emphasises that " more than these quantities should not under any circum-
stances be given ". (The italics are ours.) Buffagni [1935] gives the toxic dose of
sodium chloride for pigs as 1 grm. per kg. of body-weight and considers that
cattle should not be given more than 60 grms. per day. In some of the recent
experiments at Krishnagar (not reported here) about 60 grms. of salt were fed to
animals of about 500 to 600-lb. live-weights and no serious trouble was noticed.
There was no doubt that some animals were out of condition but this only occurred
when they were on a high dose of mustard cake. It seems, however, that in
Bengal the ordinary dose of common salt fed to the animals is a little higher than
the amounts indicated by Kellner and others. This amount although arising
out of the general usage of the country is probably an unconscious adjustment
necessitated from a larger ingestion of potash through rice straw feeding.
Relation of minerals to one another, their ratios, etc.
The interpretation of the data on mineral metabolism carries with it some
inherent difficulties in as much as there is no means by which the actual amount
absorbed or assimilated in the system can be properly ascertained. This has
led various investigators to adopt more or less empirical procedures which can
at best serve as rough guides. In fact, as Orr [1925] states " it is impossible in our
present state of knowledge to do more than make an empirical adjustment by
adding inorganic salts containing elements thought to be deficient in the rations ".
In another place [Orr, 1929] he suggests that as the amount of food needed by
the animal is determined by its energy requirement the truest basis of compari-
son is the energy unit. He has proceeded in this way and based his calculations
on energy values, on the assumption that "40 per cent of the ether extract is
digestible fat and the total nitrogen-free extractives are equal to the sum of the
digestible nitrogen-free extractives and the digestible fibre ". Although his
values were not evidently derived from direct experiments yet the conception
originated from the estimation of digestibility coefficients and are presumably
meant to be equivalent to the total digestible nutrients expressed as calories.