RELATIVE VALUE OF FEEDING STUFFS 83 
average composition and market prices of a large number of com- 
mon 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 
frequent intervals, at least every five years, 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.® 
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 is explained in another 
chapter of this book (p. 79). 
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 dgpendis. we obtain the following 
figures : 
§ Wisconsin Report 8, p. 212, 
