440 Journal of Agricultural Research voi. in, no 6 



formed which can be utilized by the organism. The heat evolved during 

 the methane fermentation, for example, constitutes part of the metab- 

 olizable energy as thus defined, although it does not enter into the tissue 

 metabolism. 



The determination of the losses of chemical energy from a single feed- 

 ing stuff or from a mixed ration is relatively simple, as is illustrated by 

 the following example taken from the results on steer B in experiment 



207. 



Computation of losses oj chemical energy from a ration 



Energy of feed: Period 1. Period 3. 



Timothyhay i2,477Cals. 12, 618 Cals. 



Grain mixture No. i 12, 549 Cals. 



Total 25, 026 Cals. 13, 618 Cals. 



Ener^ of excreta: 



Feces 7, 371 Cals. 5, 247 Cals. 



Urine I, 536 Cals. 627 Cals. 



Methane 2, 098 Cals. 1,057 Cals. 



Total 11,005 Cals. 6,931 Cals. 



Metabolizable energy 14, 02 1 Cals. 5, 687 Cals. 



Since concentrates can not be fed alone, the losses of chemical energy 

 which they suffer, like their digestibility, must be obtained by means of a 

 calculation by difference, which in period 2 of the foregoing example is 

 as follows : 



Computation of losses of chemical energy by a concentrate 



chemical Chemical energy of excreta. Jletabo* 



energy ' " lizable 



of feed. Feces. Urine. Methane. energy. 



Calories. Calories. Calories. Calories. Calories. 



Total ration 25,026 7i37i 1.536 2,098 14,021 



Computed for hay .12,477 5.254 59^ i.°°3 5.629 



Grain mixture by difference 12,549 2,117 945 i. °95 8,392 



Computed in the manner just illustrated, the losses of chemical energy 

 per kilogram of dry matter consumed in these experiments and the 

 metabolizable energy remaining are shown. in Table III, which includes 

 also the percentage distribution of the feed energy between the various 

 excreta, on the one hand, and the metabolizable energy, on the other.* 

 For convenience, the average results for the metabolizable energy per 

 kilogram of dry matter and per kilogram of digestible organic matter are 

 brought together in Table IV. 



' In all cases the obser\'ed energy' of the urine has been corrected to nitrogen equilibrium of the animal 

 by adding 7.5 Calories for each gram of nitrogen retained by the animal or subtracting the same amount for 

 each gram of body nitrogen lost, the correction being regarded as representing energy of excretory material 

 temporarily retained in the body. 



