674 NUTRITION OF FARM ANIMALS 



it is entirely possible to trace the distribution of that energy 

 in the body quite independently of any knowledge of the chemical 

 composition of the material. Not only so, ^ but it is believed 

 that in discussing energy values there are distinct advantages 

 as regards simplicity, and perhaps also as regards accuracy, in 

 cutting loose as far as possible from the conventional data re- 

 garding chemical composition and digestion coefficients and in 

 dealing directly with quantities of energy. 



This statement is by no means to be understood to stigmatize 

 comparisons based on chemical methods as either valueless or super- 

 fluous. The problems of nutrition are too complex and too difficult 

 for us to refuse any light that can be thrown on them by any method, 

 and the energy relations touch only one phase of them. The point 

 is that in whatever degree their energetic aspects can be separated 

 from their chemical aspects, to that extent we possess two inde- 

 pendent methods of approach to them. 



774. Method of computation. As already pointed out, 

 the net energy value of a feeding stuff is equal to its me- 

 tabolizable energy minus the heat production caused by its 

 consumption. It has been shown (753) that the metabolizable 

 energy of a feeding stuff, when not determined directly, may 

 be computed approximately from the total digestible organic 

 matter by multiplying by a proper factor. If from this 

 result there be subtracted the energy expenditure due to 

 feed consumption, either as directly determined or as esti- 

 mated from that of similar feeds, the remainder is approx- 

 imately the net energy value. Thus in the same two feeding 

 stuffs just used to illustrate Kellner's method each pound of di- 

 gestible organic matter, according to the averages on previous 

 pages (753-755), would contain 1.60 Therms of metabolizable 

 energy in the hay and 1.77 Therms in the bran; the average 

 losses of energy in heat production per pound of dry matter 

 would be for the hay 0.5303 Therm and for the bran 0.5339 

 Therm, and the computation of the net energy values would be 

 as follows : l - 



1 The digestible protein, carbohydrates and fats enter into the calculation simply 

 as a means of obtaining the total digestible organic matter when, as is usually the 

 case, this is not reported separately. If the latter is the case, then the computa- 

 tion is, as stated above, independent of the chemical composition. 



