290 FEEDS AND FEEDING 



horse would eat was not enough to maintain its weight when the same 

 amount of work was done at a trot. 



To keep mail-coach horses, which were pushed at top speed, in con- 

 dition, they could often be worked but one hour a day, traveling only 

 eight miles even on good roads, While a pound of additional load 

 makes but little difference to a draft horse, with running horses the 

 requirement of speed makes it necessary that the weight carried (rider 

 and saddle) be as small as possible. An ounce of additional loading 

 may make a difference of a yard or more in half a mile of running. 



453. Influence of grade. In going up a grade, the horse must not only 

 propel his body and the load over the ground but must also raise them 

 against the force of gravity. In ascending a grade of 10.7 ft. in 100 ft. 

 Zuntz found that the horse expends three times as much energy per mile 

 as when traveling on a level road. The steeper the grade, the greater the 

 energy required. For instance, in ascending a grade of 18.1 ft. in 100, 

 nearly 5 times as much energy was expended as when moving on a level 

 road. 



On the other hand, in going down a gentle incline, owing to the 

 force of gravity less energy is required than on a level road, which 

 results in a saving of nutrients. If the grade is steeper than 10 feet 

 in 100, however, the horse must expend energy in bracing himself and 

 the load against a too rapid descent and hence uses as much as when 

 traveling on the level. On a still steeper downward slope more energy 

 is expended than on a level course. Obviously, a great saving of feed 

 may be effected by a proper use of wagon brakes in a hilly country. 



454. Requirements for work horses. It has been previously pointed out 

 in Chapter VI that 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 fattening animals. With both these 

 classes, after growth is completed the ration may consist largely of 

 carbohydrates and fat, with only sufficient protein to ensure complete 

 digestion of the ration. 



It is not necessary, and is often not advisable nor economical, to 

 furnish as much digestible crude protein in the ration as stated in the 

 Wolff -Lehmann standard. (See Appendix Table IV.) Indeed, horses 

 at hard work have been fed for considerable periods without harm on 

 rations having nutritive ratios as wide as 1 :28.0 13 However, as shown in 

 Chapter III (84), when the nutritive ratio is wider than 1 : 8.0 or 1 : 10.0, 

 the digestibility of the ration is decreased and feed is wasted. It would 

 therefore not seem advisable to feed horses a ration having a wider 

 nutritive ratio than this, except possibly under unusual conditions when 

 protein-rich roughages or concentrates were not at hand, or were un- 

 usually high in price. 



"Grandeau and Alekan, Ann. Sci. Agron., 1901, II, p. 38. 



