3. Method of Measuring the Efficiency of Feeding 



Stuffs. 



The digestibility of a feed, however, is not the true measure- 

 ment of its nutritive value, for the reason that some feeds 

 require more energy for their digestion than others. What is 

 termed net energy value, expressed in the form of calories or 

 therms, represents more accurately the true nutritive values 

 of feeding stuffs. 



Explanation. — The entire amount of heat or energy con- 

 tained in a feeding stuff is termed its total heat or energy value. 

 All of this heat or energy cannot be utilized by the animal for 

 the purposes of maintaining its body in a state of equilibrium, 

 or for aiding in the production of growth and milk. The 

 several losses may be enumerated as follows : (a) the undigested 

 material, i.e., the faeces; (6) the incompletely used material of 

 the urine; (c) the work required in the processes of digestion 

 and assimilation in preparing the nutrients so that they can be 

 used for maintenance and for the production of growth and 

 milk. These several sources of loss expressed as energy, de- 

 ducted from the total energy, leave the real or net energy value. 



Here follows a table showing the relative net energy values 

 of a few of the more important feeding stuffs. Instead of 

 expressing the relative energy values in therms of energy, they 

 are stated on the basis of 100 for the sake of direct comparison. 

 The figures were secured by the use of the so-called Kellner 

 method.^ They are not perfect, but represent the results of 

 the best method that we have available at this time. Corn 

 meal is taken as 100 and the other feeds, both concentrated 

 and coarse, are compared with it: — 



Corn meal, 100.00 



Apple pomace, 10.99 



Brewers' dried grains, 65.96 



Brewers' wet grains, 17 . 78 



Buckwheat middlings, 89 . 82 



Corn bran, 77.78 



Corn silage, 12.40 



1 For a full explanation of the components of the animal body, the composition of feeds, 

 the different ways in which the food is used in the animal body, and the explanation for using 

 the therm in the calculation of rations for farm animals, see Farmers' Bulletin 346, United 

 States Department of Agriculture, prepared by H. P. Armsby. 



