280 PRODUCTIVE FEEDING OF FARM ANIMALS 



studies have been of fundamental importance, and through them we 

 are able to determine approximately the net energy that must be 

 supplied in the feed for the production of different kinds of work 

 at varying speed, on the level, or ascending certain grades, etc. 

 Zuntz found that nearly one-third {31.3 per cent) of the total of 

 feed can be converted by the horse into useful work. This is at 

 least three times greater economy than that obtained in a modern 

 steam engine. The energy required to masticate and digest feed 

 by horses was also determined by Zuntz in an elaborate series of 

 experiments ; this energy was found to vary greatly with feeding 

 stuffs of different character. In the case of hay, oats, and corn, for 

 instance, the matter stands as follows: 



Hay Oats Corn 



Pound total digestible matter in one pound 391 .615 .785 



Labor expended in chewing and digestion (in terms of 



nutrients) 209 .219 .082 



In per cent 53 35 10 



In the case of coarse feeds a considerable proportion of the 

 potential energy is consumed in the processes of mastication and 

 digestion, and hence lost for productive purposes, while with cereals, 

 grain feeds, and roots these processes require a smaller proportion 

 of the energy, and more remains for production. With some kinds 

 of straw a negative nutritive value was obtained, showing that while 

 a certain amount of heat was liberated in the digestion of the straw 

 which was ordinarily of benefit to the animal, there would be no 

 excess of energy available for production ; in fact, a larger portion 

 of nutrients than found in the straw would be required to supply the 

 energy called for by the increased internal muscular work. 



Energy Requirements of the Horse. Through the result of 

 investigations along this line that have been conducted especially 

 by German scientists we are able to calculate the energy require- 

 ments of horses for a certain piece of work. Armsby gives the 

 following example: 2 



We will suppose that a horse weighing 1100 pounds is required to haul 

 a load of one ton 20 miles a day on the level road, at a rate of 2.88 miles 

 per hour, the draft averaging 100 pounds. The useful work will be in this 

 case 



5280 (feet per mile) X 20 X 100 equals 10,566,000 foot-pounds, or 3,421 

 Calories. 



Since 31.3 per cent of the energy liberated in the body is utilized in draft, 

 it will require, to perform 3421 Calories of work, 3421 divided by .313, which 

 equals 10,929,000 Calories of energy in the body. It has been found that it 

 calls for an expenditure of energy equivalent to 264 Calories for a 1100-pound 



2 Cyclopedia American Agriculture, vol. iii, p. 88. 



