22 MISC. PUBLICATION 7 02, U. S. DEPT. OF AGRICULTURE 



gains than 5 percent (39). These results do not mean that growing- 

 fattening pigs fed in dry lot are not capable of using forages in larger 

 amounts than 10 or 15 percent of the ration. The maximum amount 

 of forage that they may use depends upon their tolerance for fiber 

 in the feeds eaten. It has been indicated that as much as 8 percent 

 of fiber in the ration is well tolerated. This level permits use of as 

 much as 20 percent of forage of 30-percent fiber content in a mixture 

 of corn, tankage, and linseed meal (7). 



Growing-fattening pigs full-fed corn and tankage on good pasture 

 not only use fewer pounds of concentrates for each 100 pounds gain 

 in weight, but gain at a more rapid rate than pigs full-fed a well- 

 balanced ration of corn and tankage in dry lot (2h pp. 89^-896). Full- 

 feeding pigs on good pasture, however, is not an absolute requirement. 

 There is considerable flexibility in the rate at which concentrates may 

 be fed without encountering unsatisfactory development of the ani- 

 mals. Rate of gain and feed required to produce a given total gain 

 in weight of the pigs are likely to differ, though, for several rates of 

 concentrate feeding. An early feeding test at the Iowa Experiment 

 Station (80) showed that pigs receiving half a corn ration on good 

 alfalfa pasture required 53 days more than pigs self-fed a corn ration 

 on the same kind of pasture to reach the weight of 225 pounds. More- 

 over, the limited-fed pigs ate a total of 29 pounds more corn and 

 tankage for each 100 pounds of gain. Results very similar to these 

 were observed at the same station when blue grass pasture supplied 

 the forage for the pigs (9). 



Economic Possibilities for Producing and Utilizing Forages in 

 Selected Farming Systems 



The foregoing summary is sufficient to indicate that in spite of gaps 

 much technical knowledge is now available regarding production and 

 use of forage crops on farms of the Northern States. But this does 

 not mean that forages are utilized in abundance in farming systems. 

 Economic considerations enter in. Farmers examine the technical 

 possibilities of producing and using larger quantities of forages in 

 terms of what these mean to costs and returns. When they know the 

 effects upon their pocketbooks, it becomes easy to act. The new idea 

 is rejected or it is accepted and incorporated into the farming systems. 

 In practice, new ideas, even though profitable, may not always be ac- 

 cepted by farmers because of some institutional barrier such as tenure 

 arrangements or because present income must be reduced so future 

 income may be increased. 



As a part of this study, production plans were developed for some 

 farms in the Corn Belt. By restricting analysis to this one area within 

 the Northern States, certain problems are brought into focus within 

 a short space better than if single farms from several areas had been 

 studied. Farms selected for consideration illustrate well-defined kinds 

 of production situations common in the Corn Belt : ( 1 ) Intensive cash- 

 grain production in which corn and soybeans are the major crops and 

 sources of income; (2) cash-grain production, resting heavily upon 

 corn with small grain as a less important source of income ; (3) general 

 farming on more rolling land — a farming system in which no single 

 product receives major emphasis. 



