ECONOMY IN FEEDING LIVE STOCK 141 



small district where the systems of farming do not vary widely, no such 

 set of values has general application to the United States. As has been 

 emphasized before (178), the value of any given feed to the stockman 

 depends on the nature and composition of the other feeds he has at hand. 

 If his chief roughage is alfalfa hay, protein-rich concentrates are often 

 worth less to him than those rich in carbohydrates. On the other hand, 

 if the cheapest roughage he can provide is corn or sorghum silage, low 

 in protein, then concentrates rich in protein will be of higher value 

 to him than those carbonaceous in character. 



In planning economical rations for any class of animals the stockman 

 should first choose from suitable feeds a combination, containing the 

 proper proportion of concentrates and roughages, which will supply the 

 necessary total amount of nutrients at the minimum expense. If this 

 ration is too low in protein, protein-rich feeds should be substituted for 

 those lower in protein, until the protein supply is brought to the de- 

 sired amount. On the other hand, if the ration which supplies the neces- 

 sary total amount of nutrients is too rich in protein, then carbonaceous 

 feeds should be substituted until the nutritive ratio is widened as much 

 as is desired. 



In determining which feeds furnish total nutrients at the lowest price, 

 the comparisons may be made on the basis of the cost per therm of net 

 energy, per feed-unit, or per pound of total digestible nutrients. For 

 the reasons pointed out in preceding articles (177-8), the authors be- 

 lieve that the most convenient system for American farmers is on the 

 basis of the cost per pound of total digestible nutrients. In comparing 

 roughages with concentrates this system gives roughages somewhat too 

 high a relative value, for 1 Ib. of total digestible nutrients in a roughage 

 is lower in net energy than 1 Ib. of digestible nutrients in concentrates. 

 However, in most cases, the desire will be, not to compare roughages 

 with concentrates, but, instead, to determine which one of several con- 

 centrates is the cheapest source of total nutrients, or which of the differ- 

 ent available roughages is the most economical feed. To determine which 

 feeds are the cheapest supplements to balance a ration low in protein, 

 it will be found convenient to compute the cost of the different feeds 

 per pound of digestible crude protein. 



In comparing the relative cheapness of different feeds, it is reasonable 

 to value marketable farm-grown grain or roughage at the market price 

 less the cost of hauling to market. Feeds which are not usually market- 

 able may be assigned a value based on the cost of production. To the 

 price of any purchased feeds should be added any cost of hauling to the 

 farm. Often, however, purchased concentrates may be brought back to 

 the farm on a return trip from market with little or no additional 

 expense. 



193. A comparison of corn-belt feeds for milk production. To illustrate 

 the manner in which the prices of the available feeds should be studied 

 in computing rations, let us assume that a dairyman in the corn belt 



