RELATIVE VALUE OF FEEDING STUFFS 83 



the average composition and market prices of a large number of 

 common feeds, and used the figures thus obtained for comparisons 

 of the cost of different feeding stuffs, but unless at least a dozen 

 different feeds are included in the calculations and these are repeated 

 at intervals of five years or oftener, the results obtained are not 

 very satisfactory. Such calculations are laborious, and the results, 

 as may be inferred, are valuable only for a limited period 

 and region. 1 



Methods of Comparison. The only methods of comparison 

 that have a general value are the three previously given, based on the 

 digestible components of feeds, . their energy values, or feed-unit 

 values. The method of comparison to be followed in each case will 

 be explained in the following paragraphs: 



(a) Digestible Components. The digestible components of the 

 feeds to be compared are added together, the per cent of digestible 

 fat being first multiplied by 2.25, and the sum divided into the 

 market prices for 100 pounds of the different feeds. The cost per 

 unit of digestible matter is thus obtained, and the feed or feeds that 

 supply a pound of digestible matter at the lowest cost are selected. 

 This method furnishes reliable information in regard to the com- 

 parative value of feeds of the same kinds, rough feeds, concentrates, 

 roots, etc., but not when feeds of different classes are compared, on 

 account of the greater losses of energy in the digestion of coarse 

 feeds than in the case of concentrates. 



(b) Energy Values. The net energy values for 100 pounds of 

 the different feeds are divided into the price per 100 pounds, and 

 the feed or feeds furnishing a unit of energy value (therm) at the 

 lowest cost thus ascertained. These values are reliable for produc- 

 tion of increase in body weight in the case of fattening steers, and 

 approximately so also for other purposes of animal production. 



(c) Feed-unit Values. The cost of a feed unit is determined 

 by multiplying the cost per 100 pounds by the feed-unit value of 

 each feed. The lowest cost per feed unit shows the cheapest feeds. 

 The origin and meaning of the feed-unit system was explained in 

 the preceding chapter. 



Example 1. Given green corn fodder at $2 per ton; alfalfa hay 

 at $10 a ton; corn at 60 cents a bushel ($21.40 a ton) ; wheat bran 

 at $24, and linseed meal at $30 a ton, which feeds are most economi- 

 cal for feeding dairy cows? 



By reference to Table I in the Appendix, we obtain the follow- 

 ing figures : 



1 Wisconsin Report 8, p. 212; Woll, Handbook for Farmers and Dairy- 

 men, 6th Ed., p. 20. 



