870 The Feeding of Animals 



These figures are, perhaps, less important to the 

 owner of work or driviDg" 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. G2 for canter- 

 ing, and G8.39 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 w^ay 

 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 lbs. of hay when he walked 12% miles, but 

 24 lbs. 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 lbs., 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 

 6/3 to 1/i miles per hour. The food needed per unit 

 of w^ork 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 



