288 FEEDS AND FEEDING 



cover the amount used up in the internal work of the body and in repair- 

 ing the body tissues. 



This conclusion accords with the general experience, that idle horses 

 can be maintained chiefly on such feeds as hay, corn stover, and straw, 

 which furnish relatively little net energy but produce a large amount of 

 heat in the body as the result of mastication and digestion. If the rough- 

 ages are of sufficiently good quality, the animals may be maintained on 

 such feeds alone. As roughages are usually far cheaper sources of total 

 available energy than the concentrates, maintaining idle horses on such 

 feeds is obviously economical. 



In addition to supplying sufficient fuel to maintain the body tempera- 

 ture and enough net nutrients for the internal work of the body, as has 

 been previously pointed out (93), the nutrients in the ration must include 

 a certain amount of digestible protein to make good the small daily waste 

 of nitrogenous tissues. In experiments by Grandeau and LeClerc, horses 

 were maintained for periods of 4 to 5 months on rations of meadow 

 hay which furnished an average of only 0.54 Ib. digestible protein 

 daily per 1,000 Ibs. live weight. Most authorities maintain, and practical 

 experience shows, that the health of animals is improved when they are 

 fed more than the theoretical minimum of protein. In view of this, in 

 the Morrison feeding standard 0.8 to 1.0 Ib. of digestible crude protein 

 per 1,000 Ibs. live weight is recommended for maintaining idle horses. 

 (Appendix Table V.) 



449. Nutrients required in various types of work. It is evident that the 

 horse at work must receive a larger supply of nutrients than when idle, 

 and that the amount needed will depend on the severity of the work done. 

 Let us then consider what types of work the horse performs. His work 

 usually consists of a more or less complex combination of the following 

 simple kinds: (1) Locomotion, or traveling along a level course without 

 a load; (2) raising the body, with or without a load, against the force 

 of gravity in ascending a grade; (3) carrying a load; (4) draft, or haul- 

 ing a load. A horse drawing a load up a hill combines all of these types. 

 He is (1) advancing and at the same time (2) raising his body. Likewise 

 he is (3) carrying the harness and (4) hauling the load. In descending 

 the hill the horse will be called upon to perform even a fifth type of 

 labor, bracing himself to prevent too rapid a descent. 



Much experimental work was done many years ago by Wolff, Grandeau 

 and LeClerc, and more recently by Zuntz and his associates to determine 

 the amounts of nutrients required in the various types of work. Wolff's 

 experiments were with a sweep-power constructed so that the amount of 

 work performed could be measured. Zuntz, in conjunction with Lehmann 

 and Hagemann, conducted hundreds of tests with horses working on a 

 tread-power so built that the distance traveled and the work performed 

 were accurately measured. The animals breathed thru a tube inserted 

 in the windpipe, by which means the oxygen inhaled and the carbon 

 dioxid exhaled were accurately determined. To such gaseous intake and 



