FOODS ANIMAL PRODUCTION. 1021 



fiber, tiudergo the greatest amount of variation, their digestibility rising consider- 

 ably with exercise and falling still more considerably with hard labor. In the case 

 of the more insoluble portion of the fiber there is no rise in digestibility by exercise; 

 the maximum rate of digestion is here obtained in repose, and diminishes consider- 

 ably w itb increased bodily exertion. On the whole it appears that the constituents 

 of the food which are most affected by rapid exertion are those whose digestion takes 

 place to a large extent in the lower part of the intestines; the motion of the horse 

 probably determines their more rapid passage through the system." 



Grandeaii's experiments have brought out the marked influence of 

 pace on the amount of labor performed and the food required. 



"Thus a horse Avalking 12^ miles per day was kept in condition with a daily 

 ration of 19.4 lbs. of hay, while a ration of 24 lbs. of hay was insufficient when the 

 same distance was done trotting. Again, a horse walking the above distance and 

 dragging a load, the additional work being equivalent to 1,943 foot-tons, was suffi- 

 ciently nourished by a ration of 26.4 lbs. of hay ; but a daily ration of 32.6 lbs. (all 

 that the horse would eat) was not enough to maintain the horse's weight when the 

 same work was done trotting." 



Some of the reasons mentioned why rapid work is less economical 

 than slow work are the increased work of the heart when the horse is 

 trotting or galloping; the lifting of his own weight at each step, only 

 to allow it to fall again, developing heat; the increase of temperature 

 with exertion, and the loss of heat by evaporation of water through 

 the skin and lungs. 



"The mean quantity of water evaporated daily, under different conditions of exor- 

 cise, as determined in experiments with 4 different diets, was as follows: 



Water evaporated per day. 



Pounds. ' 



At rest 6. 4 



Walking exercise 8. 6 



At work walking 12.7 



Trotting 13.4 



At wor.i trotting 20. 6 



"As already explained, the distance trotted was the same as the distance walked, 

 and the load drawn when trotting the same as when walking. The heat consumed 

 in the evaporation of water is very considerable; the loss of water in the breath and 

 perspiration thus necessitates a consumption of food to produce this heat, and 

 diminishes considerably the quantity of food available for the production of work." 



As to whether a nitrogenous ration is or is not essential for horses at 

 hard work, it is said that Graudeau's researches do not furnish any 

 information, but that we have to rely chiefly on the investigations of 

 Wollf and of Muntz. 



" The doctrine laid down by Wolff and his fellow-workers at Hohefnheim is a very 

 simple one. He distinguishes between the food necessary to maintain the horse at 

 rest without loss of weight and the extra food which must be given when work is 

 performed, if the horse is again to be maintained without its weight suffering loss. 

 Between the weight of digestible matter in this extra food and the quantity of work 

 accomplished there is a tolerably uniform relation. Wolff reckons that digested nutri- 

 tive matter equivalent to 100 gm. of starch is capable of producing 85,400 kilogram- 

 meters of work, or, expressed in English terms, 1 lb. of starch digested by a horse 

 will accomplish 1,232 foot-tons of work. This is 48 per cent of the full work which 



