AN IMPROVED METHOD OF COMPUTATION OF NET- 
ENERGY VALUES OF FEEDING STUFFS 1 
By Max Kriss 
Institute of Animal Nutrition, Pennsylvania State College 
INTRODUCTION 
The computation of net-energy values of feeding stuffs from data 
obtained by means of the respiration calorimeter has been explained 
in many publications by Armsby and Fries (1 to 9 ). 2 The general 
principle upon which these computations are based is well Known 
and well understood. Essentially it involves the deductions, from 
the gross energy of the feed, of the entire expense of utilization of 
the feed energy for maintenance and production. 
While the net-energy conception as promulgated by Armsby 
remains unaltered, the method of computation of net-energy values 
followed by Armsby and Fries in their later publications differs in 
detail from that .used by them in the earlier reports, these differences 
representing improvements resulting from knowledge gained in the 
course of the experiments. 
A further study of this computation in the light of present under¬ 
standing has led to other improvements as here set forth. 
DISCUSSION 
The examples given will serve to illustrate the advantage of the 
latest modification, as compared with the earlier procedures. 
Table I, Part A, quoted from Armsby’s Nutrition of Farm Animals 
(8, p. 272 ), is given in that work as an illustration of the method of 
computing net-energy values for maintenance. 
Two periods in which different amounts of timothy hay were fed are 
compared. The gain of energy is determined for each period by 
subtracting the heat production from the metabolizable energy. 
The difference in gain between the two periods, divided by the 
difference in feed eaten, represents the net energy per unit of feed. 
More specifically, the net-energy value of the hay is 2,028 4.04 = 502 
calories per pound of dry matter. 
It will be noticed that the same result may be obtained in this 
case by subtracting the heat increment per pound of dry matter of 
hay (433 Calories) from either the metabolizable energy per pound 
of dry matter of the hay eaten (935 Calories) or from the metabolizable 
energy per pound of dry matter of the added hay, these two values 
being identical. This occurrence is explained by the fact that the 
metabolizable energy per pound of dry matter oi the hay is exactly 
the same in both periods which are compared. This is, however, 
rarely the case in practical experiments. The numerous sources of 
1 Received for publication Oct. 22, 1924; issued October, 1925. 
2 Reference is made by number (italic) to “Literature cited,” p. 484. 
Journal of Agricultural Research, 
Washington, D. C. 
( 469 ) 
Vol. XXXI, No. 5 
Sept. 1,1925 
Key No. Pa. 14 
