368 The Feeding of Animals 



it now remains for us to ascertain what is known con- 

 cerning energy consumption by a laboring animal. 



The work performed by a horse. The labor per- 

 formed by a draft or road animal, exclusive of the 

 energy required for maintenance, may be regarded as 

 consisting of two components; viz., the effort of mov- 

 ing the load and that of moving the animal's body. 

 If a horse weighing 1,000 Ibs. draws one mile a wagon 

 which, with its load, weighs 1,500 Ibs., 2,500 Ibs. of 

 matter have been moved through the distance traveled. 

 In other words, a horse moves himself and his load, 

 whether the load is drawn on a wagon or is loaded on 

 his back. 



The exact expenditure of energy involved in both 

 of these components cannot be measured directly. The 

 work of drawing a load may be determined by the use 

 of a dynamometer, but it can only be estimated so far 

 as the body of the horse is concerned. If the latter 

 factor could be calculated on the basis of simply pro- 

 jecting a mass of matter through the space traveled 

 it would be a comparatively simple problem. There is 

 a vertical motion of the horse's body to be accounted 

 for, as well as a horizontal, and the reduction of both 

 to units of work is a difficult matter. If this could 

 be done, our present knowledge of the food energy 

 necessary for the performance of a unit of mechani- 

 cal labor would allow quite definite calculations of the 

 daily food needs of horses of different classes. As a 

 matter of fact, the actual work accomplished by labor- 

 ing animals has been to quite an extent a matter 

 of estimation, and still is. 



