Pigs possess two characteristics which make them unique among domestic animals. They consume concentrated and easily digested foods only, and they produce nothing but meat, fat and bristles. Cattle furnish milk and hides; sheep, wool, hides and sometimes milk; fowls furnish eggs and feathers. On account of their limited range of usefulness and because of the high value of much of the food consumed, it would not be possible to rear swine economically were it not for their prolificacy and the fact that they are employed largely as scavengers. Many cattle are fattened without direct profit. The indirect profit comes from the sale of the pigs which have followed the cattle. It is customary to mature one hog with little or no additional food while fattening two steers. In many well-known ways, pigs consume products which would otherwise be wasted. This is especially true in the more densely settled sections of the world. On account of their prolificacy, the returns obtained for the amount of capital invested is greater than in the case of sheep, cattle or horses. Ten sows, worth $100 to $150, are sufficient to produce 100 pigs; 75 to 80 ewes, worth from $300 to $500, are required to produce an equal number of lambs; 110 cows, worth $4,500 to $6,000, to produce 100 calves; and 200 mares, worth from $20,000 to $30,000, to guarantee 100 foals. To put the matter in another way, the capital invested in swine may be reproduced in the offspring ten times in one year; the capital invested in horses not more than once in five years. In general, 500 pounds of maize will produce 100 pounds of pork, which is equivalent to eleven pounds of pork from a bushel. Since hogs are so largely produced from maize, the price of maize and the price of pork are very closely related. For example, if maize is worth fifty cents a bushel, the grain required to produce a pound of increase in live weight will cost about 5 cents; if 40 cents a bushel, 4 cents; if 30 cents a bushel, 3 cents; and so on. COST OF PRODUCING SHEEP In the classic investigations by Lawes and Gilbert, food containing 100 pounds of dry matter produced a live-weight increase of nine pounds in steers and 11 pounds in sheep. At the Wisconsin station, sheep required less food than steers per pound of gain. During rapid fattening of sheep 500 pounds of clover hay and 400 pounds of maize may produce 100 pounds of increase in live weight. While swine require a less weight of food for a pound of increase than sheep, on account of the more digestible character of the food eaten, yet the Wisconsin station found that the expense of producing a pound of increase was less in sheep on account of the less expensive character of the food. MEAT AND MILK PRODUCTION COMPARED