(1) The injection of an anti-cholera serum, which makes the hog immune only a few months or weeks. (2) The simultaneous treatment whereby the serum used in (1) and the defibrinated blood or virus from a diseased hog are injected together. This treatment renders the hog immune for life. (3) In the combination method, serum alone is used first, and ten days later the simultaneous treatment is administered. This method is seldom used. The services of a skilled veterinarian should be secured to vaccinate hogs. =Feeds and feeding.= Protein, fats, and carbohydrates are the three classes of nutrients found in feeds. These, in addition to mineral matter and water, furnish material for the maintenance and growth of the pig. Proteins furnish the material for the production of muscle. Fats and carbohydrates provide fuel for heating the body and giving activity to the muscles. An excess of food nutrients, especially fats and carbohydrates, is stored in the body as fat. The mineral matter goes into the production of bone. All feeds do not contain these nutrients in the same proportions. Some feeds, like corn, are deficient in protein, while others, like tankage, contain a large percentage of protein. [Illustration: 15. A SELF-FEEDER] From the foregoing it is easily seen that the problem of the hog raiser is to use a combination of feeds which will provide the proper proportions of the various nutrients. While the pigs are young, bone and muscle producing foods are especially necessary. Toward maturity the percentage of fat producing foods may be increased. =Corn, pasture and other supplements.= Corn is the most widely used feed for pigs. As has been stated, it is essentially a fat producing food and must be properly supplemented. Clover or alfalfa pasture supplies the protein and part of the mineral matter which the corn lacks. Rape furnishes good pasture for hogs, almost equal to clover and alfalfa. Rye, blue grass, cow peas and soy beans together with various pasture mixtures have value as hog pastures. Where pigs are fed in a dry lot, tankage may be used to supply the protein. Pasture-fed pigs are thriftier and make cheaper gains than those fed in a dry lot. Skim-milk or buttermilk together with tankage makes an ideal supplement to corn. Middlings and shorts may also be used. =Mineral matter.= To insure pigs getting enough mineral matter it is recommended that the following mixture be kept before them at all times:[7] Wood ashes or coal screenings 1 bushel Air-slaked lime 8 quarts Salt 8 quarts Rock phosphate 3 quarts Copperas (iron sulphate) 1 quart The first four ingredients should be mixed thoroughly and the copperas dissolved in warm water and poured over the mixture.