Economic efficiency of the hog ration is extremely important in Iowa. Pork is the leading source of farm income in the state. The income from pork has been 54 percent higher than that from cattle over the past ten years. The importance of the economy of the hog ration in Iowa agriculture also is indicated by the fact that feed costs constitute from 70 to 85 percent of the total cost of production. Hence improved efficiency of the hog ration will make important contributions to individual farmers and consumer welfare.

Economy in the hog ration depends especially on the manner in which feeds are combined. Many feeds can be used in pork production and they can be combined in many ways. A number of carbohydrate feeds such as corn, barley or wheat can be substituted for each other and used in combination. On the other hand, vegetable proteins such as soybean oilmeal, linseed oilmeal and cottonseed oilmeal, and animal proteins can also be substituted for each other or used in combination. Finally, supplementary proteins and carbohydrate feeds can be substituted for each other and used in many combinations. One of the main economic problems in hog rations is this: What combination of corn and protein should be used in producing 100 pounds of pork 1 While other carbohydrate feeds sometimes have a more favorable price and supply situation, corn-aside from oats-has had the traditional advantage, both in price and proximity.