102 PRINCIPLES OF FEEDING FARM ANIMALS 



cases, the requirements for heat production, is available to 

 the animal for the work of the voluntary muscles, such as 

 walking, puUing, carrying, etc. However, not all the net 

 energy available for the production of voluntary work can 

 be recovered in the form of work. A certain amount is 

 lost in the form of heat during the transformation. This 

 loss may be compared to the loss of energy as heat occurring 

 in any gas, gasoline, or other internal combustion engine. 

 The gas is oxidized or exploded in the cylinders of the engine 

 with the liberation of energy. In a comparable manner 

 the digested and absorbed nutrients of the feed are oxidized 

 in the cells of the muscular tissue of the animal with the 

 Hberation of energy. In either ^case, a considerable part 

 of the energy liberated is not recovered as work but is lost 

 in the form of heat. Anyone who has had experience with 

 gas engines is famihar with the fact that only a fraction of 

 the energy of the fuel can be recovered as work. A similar 

 loss occurs in the cells of the muscles of the animal. When 

 the nutrients are oxidized, a considerable amount of the 

 energy {i.e. the net energy of the feed) is lost in the form 

 of heat. Thus, on a cold day one walks faster, or slaps his 

 arms, or stamps his feet, or shivers in order that the body 

 may have the benefit of the heat which is generated in the 

 performance of this work. 



Coefficient of Utilization. — The percentage of the energy 

 of the fuel which may be recovered by a motor in the form 

 of work is known as the " coefficient of utilization." The 

 coefficient of utilization with respect to the animal takes 

 account only of the loss which occurs in the conversion of 

 the net energy into work. That is, it is the percentage of 

 the net energy of the ration (not the gross energy of the fuel 



