This section is from the book "The Potato: A Compilation of Information from Every Available Source", by Eugene H. Grubb, W. S. Guilford. Also available from Amazon: The Potato: A Compilation Of Information From Every Available Source.
On A basis of strict economy as regards the use of the world's supply of foodstuffs, it would probably never be right to feed potatoes fit for human food to livestock.
Granting this, the potato has yet a place of some importance as a stock food. There are thousands of tons of small, cut, bruised and diseased potatoes produced annually in potato districts that should be converted into high-class animal products. In addition to this, there are the by-products of the various manufacturing processes in which the potato is used The feeding of potatoes and potato products has been practised more in Europe than in America, because the American farmer has had, since the beginning of agriculture in this country, an abundance of cheap grains for stock feeding.
We have undoubtedly seen the last of extremely low-priced grains - so that the heavy cropping, succulent potato, should have a place of increasing importance as one part of stock feed rations.
In "Farmers' Bulletin 79 " of the United States Department of Agriculture is the following interesting information:
A number of French agriculturists have recently studied the desirability of ensiling potatoes.
A considerable amount of heat is generated by the fermentation of the green material in silos, and it was thought this could be utilized and the potatoes could be cooked as well as preserved.
In one test the potatoes were buried in a silo filled with crimson clover. They acquired the characteristic color of the plant and the odor developed in fermentation. The tubers were flattened by the heavy pressure to which they had been subjected. When removed from the silo they were comparatively soft. They were examined microscopically and chemically, and it was found that they had been cooked by the heat of fermentation, and that they were rendered more digestible by the process; that is, the percentage of soluble material was increased.,
Another silo was filled by surrounding about a ton of potatoes with corn (whole plant). Upon opening, the corn and potatoes were both found in good condition. The tubers were found somewhat flattened, as in the previous experiment, but were more cohesive. The potatoes were not as thoroughly cooked, since the temperature and pressure were less than in the previous case.
As shown by analysis, the potatoes ensiled with crimson clover had lost less water than those ensiled with corn. The most striking difference, however, was the high percentage of cooked starch; or in other words the increased assimilability of the potatoes ensiled with clover. The crushed potatoes when removed from the silo lost weight very rapidly on exposure to the air, and formed a hard mass, containing only 15 to 20 per cent. of water. In this condition they could be kept for a long time. When required for feeding purposes they were soaked in water, which they readily absorbed and thus regained their softness and digestibility.
Another investigator ensiled chopped raw potatoes with two pounds of salt per 1,000 pounds of potatoes, under pressure of 2,500 pounds per square yard. The total cost of washing, chopping, putting in the silo, and weighing fifty tons of potatoes was about $15. The potatoes were put in the silo in the latter part of November. When the silo was filled the material was five and a half feet deep. Sixty-two days later the silo was opened, and the mass had sunk to a little over three feet. The temperature of the silo when filled was 39 degrees F., and when opened it was 50 degrees. The ensiled potato pulp was white, but became blackened on exposure to the air. Cattle ate this pulp greedily, alone or mixed with cottonseed cake.
Experiments made at the Minnesota station have shown that while the digestibility of cooked and raw potatoes by pigs was about the same, pigs could be induced to eat larger quantities of cooked potatoes. It was calculated that a ration of fifteen pounds of potatoes and four pounds of shorts would furnish an amount of protein sufficient for maintenance, leaving a margin for growth.
On the basis of cost, comparisons were made of the value of potatoes and other feeding stuffs. In the investigator's opinion, with foods at the present prices, it is doubtful whether it would be profitable to feed large amounts of potatoes to dairy stock, because cows require more protein than would be supplied by a fattening ration similar in character to that mentioned above.
Potatoes cannot be fed to young animals as safely as to more mature ones, since if fed in too large quantities they have a tendency to prematurely fatten the animal. With mature animals when the object is principally the addition of fat to the body, potatoes may be fed to good advantage.
When the crop of potatoes is large and prices low, a method of storing and feeding potatoes to advantage is desirable.
A method of preserving potatoes which at the same time cooks them would seem worthy of trial, but it would doubtless be wise to experiment on a small scale first."
John M. Scott, in Florida Agricultural Experiment Station "Press Bulletin 71," says:
In all feeding experiments it has been found that rations containing a high percentage of carbohydrates (fat and heat producing material) do not give good returns in producing meat; but if sufficient protein (muscle and bone producing material) is added, so as to give the animal a balanced ration (or one nearly balanced) the results are generally satisfactory. It makes little difference in what feeds the carbohydrates are furnished so long as the material is digestible. Since sweet potatoes are a crop easily grown, give good yields, are well adapted to the soils and climate of Florida, and contain a large percentage of carbohydrates, some notice should be taken of them, and they deserve to be studied in order to find out their value as a feed for pork production.
It has been pretty clearly demonstrated that sweet potatoes when fed alone are a poor feed for pork production. This is due to the fact that sweet potatoes contain such a large amount of carbohydrates and such a small percentage of protein. The results of these experiments may be summarized as follows: