284 FEEDS AND FEEDING 



most cheaply. Yet he may forget that similar principles apply to the 

 feeding of his work animals. An average of about 4 horses or mules are 

 kept on each farm in the United States. When we learn in Chapter 

 XIX how it is often possible thru the economical and proper selection of 

 feeds and their rational administration to save 10 to 40 per ct. of the 

 usual feed bill, with no injury, and in some cases even a benefit to the 

 animals, it is evident that a careful consideration of the principles 

 governing the feeding of horses will pay every owner in dollars and cents. 

 Furthermore, it is just as essential to care for work animals so as to 

 ensure their maximum efficiency as it is to lubricate carefully the vehicles 

 and machinery they draw. 



Before studying in detail the feeds for the horse and the methods of 

 feeding and care, it is necessary to consider briefly the principles deter- 

 mining the value of the different classes of feeds for the production of 

 work and the various factors which influence the amount of labor the 

 animal can perform. 



Most of the discussions which follow treat of the horse particularly, 

 since about 78 per ct. of our work animals are horses, and nearly all of 

 the scientific trials have been conducted with them. The same feeds may 

 be used for mules, however, and the same principles of feeding and care 

 apply to these animals. (Special hints on the feed and care of the mule 

 are given in Art. 532. ) 



I. FACTORS INFLUENCING THE WORK DONE BY HORSES 



444. Work done by horses. In measuring work, the units are the 

 foot-pound and the foot-ton. A foot-pound is the work done in lifting 

 one pound one foot against the force of gravity; and a foot-ton the 

 amount done in lifting one ton one foot against gravity. The rate at which 

 work is performed is measured in terms of horse-power. A horse-power 

 is the power required to lift 33,000 Ibs. at the rate of 1 ft. per minute, 

 or to lift 1 Ib. at the rate of 33,000 ft. per minute. To illustrate, a 

 horse drawing up a loaded bucket weighing 100 Ibs. from a well 330 feet 

 deep in one minute exerts a force equal to 1 horse-power. 



The work which horses can do depends on their weight, muscular 

 development, and endurance. At steady and continuous work for 10 

 hours a day, the pull or draft for a horse should not be more than one- 

 eighth to one-tenth its weight. The daily work performed by horses 

 of different weights would then be about as follows 2 : 



Daily work performed by horses of different weights 



Horse-power produced Foot-tons of work done 



800-lb. horse 0.530.67 5,247 6,633 



1000-lb. horse 0.670.83 6,6338,217 



1200-lb. horse 0.80 1 .00 7,920 9,900 



1400-lb. horse 0.93 1 .17 9,20711,583 



1600-lb. horse 1 . 061 . 33 10,49413,167 



z King, Physics of Agr,, p. 490. 



