Energy Expenditure by Horses 369 



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 an 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 evidently meaning the mechanical labor out- 

 side the motion of the body. With the knowledge we 

 now possess it is possible to estimate approximately 

 the actual work performed in a given case. 



It would be a good day's labor if a 1,000-lb. horse 

 travels twenty miles over a smooth, level, dirt road 

 hauling a wagon with a load of 2,000 Ibs. The draft 

 of the loaded wagon would be not far from 100 Ibs. 

 A simple calculation shows that the mere moving of 

 such a load the distance of one mile would be equiva- 

 lent to 264 foot tons. The energy expenditure in 

 walking a given distance has been measured by Zuntz, 

 who ascertained the difference in oxygen consumption 

 of a horse when at rest and when traveling at a 

 walk over a level road. According to these meas- 

 urements, it appears that a 1,000-lb. horse in walking 

 one mile at the rate of two to three miles per hour 

 would expend a total energy of 473 foot tons, 44.4 

 per cent or 201 foot tons of which belong to the 

 effort of walking over and above the energy needed for 

 mere maintenance. In the case assumed, a horse would 

 perform a total labor in walking and drawing twenty 

 miles equivalent to lifting 9,300 tons through a space 

 of one foot. This estimate is presented merely as an 

 approximation of the work done under given conditions. 



