The constituents of the potato are according to different authorities,
as follows:
Water 75.2
Casein 1.4
Starch 15.5
Dextrine 0.4
Sugar 3.2
Fat 0.2
Fibre 3.2
Mineral matter 0.9
Or economically:
Water 75.2
Flesh-formers 1.4
Fat-formers 18.9
Accessories 3.6
Mineral matter 0.9
Of the high value of potatoes, when used in connection with other food,
there is not a shadow of doubt. All experimenters and observers in the
economy of food agree in saying that they are of the highest utility;
but they must be used with other food whose constituents are different
from those of the root.
The analysis shows that potatoes surpass in the fat-producing principles
the nutritious or flesh-forming in such proportions that they could not
alone sustain the composition of the blood; for an animal fed alone on
these tubers would be obliged to consume such quantities to provide the
blood with the requisite proportion of albumen that, even if the process
of digestion were not discontinued, there would be a superabundance of
fat accumulated beyond the power of the oxygen to consume, which would
successively absorb from the albuminous substance a part of its vital
elements, and thus a check would be caused in the endless change of
matter in the tissues in the nutritive and regressive transformations.
Potatoes, then, to be of most value as food for cattle, should be fed in
connection with grain, or with other roots in which the flesh-forming
element predominates. There seems to be no doubt that the tubers are of
most value when cooked, although some authors affirm to the contrary. It
seems possible to prove this on philosophical principles; for it is well
known that the starch contained in the potato is incapable of affording
nourishment until the containing globules are broken, and one of the
most efficient means of doing this seems to be by heat.
Boussingault, in speaking of the economy of cooking potatoes, says, "The
potato is frequently steamed or boiled first; yet I can say positively
that horned cattle do extremely well upon raw potatoes, and at
Bechelbrunn our cows never have them otherwise than raw. They are never
boiled, save for horses and hogs. The best mode of dealing with them is
to steam them; they need never be so thoroughly boiled as when they are
to serve for the food of man. The steamed or boiled potatoes are crushed
between two rollers, or simply broken with a wooden spade, and mixed
with cut hay or straw or chaff, before being served out. It may not be
unnecessary to observe that by steaming potatoes lose no weight; hence
we conclude that the nutritive equivalent for the boiled is the same as
that of the raw tuber.
"Nevertheless, it is possible that the amylaceous principle is rendered
more easily assimilable by boiling, and that by this means the tubers
actually become more nutritious. Some have proposed to roast potatoes in
the oven, and there can be little question that heated in this way they
answer admirably for fattening hogs, and even oxen. Done in the oven,
potatoes may be brought to a state in which they may perfectly supply
the place of corn in feeding horses and other cattle."
The apparent contradiction in the remarks will be observed; but the
evident leaning in favor of cooked potatoes shows that Boussingault,
although paying some attention to the theory that cooked food is not
generally attended with the same benefit to ruminating as to other
animals, was evidently almost convinced that those which contained an
abundance of starch in their constituents must be rendered more
nutritious when exposed to the action of heat.
Potatoes fed in a raw state to stock are laxative in their effects, and
are often given to horses as a medicine in cases of "hidebound" with
decided benefit. Bots, which have been known to live twenty-four hours
immersed in spirits of turpentine, die almost instantly when placed in
potato-juice; hence a common practice with horsemen, where bots are
suspected, is to first administer milk and molasses to decoy the
parasites from the coating of the stomach, and then drench the animal
with the expressed juice of potatoes. A decoction made by boiling the
parings of potatoes in a small quantity of water is often used as a wash
to kill vermin on cattle. Raw potatoes, fed occasionally and in small
quantities, are a good tonic for stock of any kind which is kept
principally on hay; but all experiments show that when the potato is
used for fattening purposes, the tubers should in some way be cooked,
that the animal to which they are fed may derive from them the greatest
possible amount of nutriment. Repeated experiments demonstrate the fact
that horned cattle or hogs lay on as much fat from the consumption of
two thirds of a given quantity of potatoes properly cooked as they will
by eating the entire quantity in a raw state. In point of nutriment as
cattle-food, two pounds of potatoes are considered equivalent to one
pound of hay.