370 The Feeding of Animals 



These figures are, perhaps, less important to the 

 owner of work or driving horses than is a knowledge 

 of the influence of speed upon the labor expended in 

 a unit of time. "According to Marcey, the work 

 accomplished in a given time is proportionate to the 

 square of the velocity. His coefficients were 3.42 for 

 walking or pacing, 16 for trotting, 28.62 for canter- 

 ing, and 68.39 for a full gallop." This general fact 

 would be applicable to horses under all conditions of 

 labor. Moreover, it is clearly demonstrated by two in- 

 vestigators that the food energy required for a unit of 

 work increases with the speed. In other words, a 

 horse that trots 20 miles a day must have more food 

 than when he walks the 20 miles. In the same way 

 draft animals require food somewhat in proportion to 

 the pace with which they travel over a given distance. 

 Grandeau has shown that a horse was kept in condition 

 with 19.4 Ibs. of hay when he walked 12% miles, but 

 24 Ibs. was insufficient when he trotted the same dis- 

 tance. Zuntz measured the oxygen used per meter 

 kilogram when a loaded horse traveled at different 

 velocities. When the pace was three miles per hour, 

 with a load of 275 Ibs., the energy required was equal 

 to 4,600 calories for each kilogram meter of horse, 

 which increased to 7,753 calories when the speed reached 

 6% to 7% miles per hour. The food needed per unit 

 of work increased nearly 70 per cent in increasing the 

 speed from 3 miles to 7 miles. Zuntz shows that if a 

 horse exerts himself to the utmost the use of oxygen 

 rises at a rapid rate, and that the food consumed per 

 unit of work is nearly one -half more than with ordinary 



