388 THE FEEDING OF ANIMALS 



482. 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 consist- 

 ing of two components, viz., the effort of moving the 

 load and that of moving the animal's body. If a horse 

 weighing 1,000 pounds draws 1 mile a wagon which, with 

 its load, weighs 1,500 pounds, 2,500 pounds 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 projecting a mass 

 of matter through the space traveled, it would be a com- 

 paratively 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 per- 

 formance of a unit of mechanical 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 laboring animals has been and still is 

 to quite an extent, a matter of estimation. 



Chardin, a French army veterinarian, estimates that 

 the average daily work performed is about 2,580 foot- 

 tons. Lavalard calculates that the total ordinary work 

 of any army horse equals 8,500 foot-tons. As stated by 

 Armsby, the ordinary day's work of a horse is estimated 

 at 1,500,000 kilogram meters, or 5,425 foot-tons, this 



