FEEDING AND CARE OF HORSES 



223 



only one-fourth as much, and more energy is actually spent in digesting 

 and masticating wheat straw than it supplies. Hence, it has a negative 

 value for producing work, tho it may aid in keeping a horse warm. 

 Carrots yield but a small amount of work per pound, due to their 

 watery nature. It is clear from this table that the harder a horse 

 works, the greater must be the proportion of concentrates, such as corn, 

 and oats, in his ration, and the smaller the proportion of roughages, as 

 hay and straw. 



Types of work performed by the horse. — 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 per- 

 forms. His work usually con- 

 sists 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 with- 

 out a load, against the force 

 of gravity in ascending a 

 grade; (3) carrying a load; 

 (4) draft, or hauling 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, brac- 

 ing himself to prevent too rapid a descent. 



The amount of nutrients required in each of these types of work has 

 been determined in careful experiments. However, the results are of 

 theoretical rather than practical interest, for the work of most horses 

 varies greatly from day to day and is usually of a complex nature, 

 difficult to divide into these simple types. All that can commonly be 

 done is to estimate whether the horse is. performing light, medium, or 

 heavy work, and then compute a ration which meets the standard for 

 this degree of labor. As we have seen in Chapter VI, normally the 

 carbohydrates and fats furnish the energy used in producing work, and 

 no more protein is usually broken down during work than during rest. 

 Hence, the nutrient requirements of horses at work resemble those of 



Fig. 63. — The conformation of the draft 

 horse, developed by years of breeding, fits 

 him to haul heavy 'loads at a relatively 

 slow pace. 



