42 



FEEDS AND FEEDING, ABRIDGED 



ing it and assimilating the digested nutrients. The energy so 

 expended finally takes the form of heat, but is wasted so far as other 

 uses are concerned. That portion of the energy which remains after 

 masticating, digesting, and assimilating the food is termed the net 

 energy of the food. This net energy is used by the animal, first of 

 all, in the work of the heart, lungs, and other internal organs, and in 

 case a surplus of net energy then remains, such surplus may be used 

 for producing growth, fat, milk, or wool, or in the performance of 

 external work. 



The losses of energy due to mastication, digestion, and assimilation 

 may be compared to the losses which would occur if a gasoline engine 

 had to distil its own gasoline from crude petroleum and then get rid of 

 the impurities which it could not use. 



Net energy of feeding stuffs. — Our knowledge of the net energy 

 value of different feeds has been obtained largely thru the pains- 

 taking experiments conducted by Kellner in Germany and Armsby 

 in this country. The following table sets forth some of their findings 

 with reference to what becomes of the digestible nutrients and three 

 common feeding stuffs when fed to the ox : 



Net energy from 100 lbs. of digestible nutrients and common 

 feeding stuffs 



The first column of the table shows the total amount of energy which 

 would be produced on burning 100 lbs. of the digestible nutrients or 

 of typical feeding stuffs. With the digestible nutrients no further 

 loss occurs in the feces, but all are absorbed out of the small intestine 

 and go into the body proper. The oil contained no nitrogen, and so 

 no nitrogenous waste from it appeared in the urine, nor did any of it 

 form methane (marsh) gas in the intestines. To digest and assimilate 

 this 100 lbs. of oil required 174.4 therms of energy, leaving 224.8 

 therms as the net energy value for growth, fattening, work, or milk 

 production, 



