X.] 



FOOD REQUIREMENTS OF HORSES 



199 



after deductions have been made for energy spent in 

 digestion, etc. As different foods possess different 

 amounts of available energy, Zuntz has constructed the 

 following table for the horse : — 



Table XIX.— Available Energy of Various Foods. 



This table means that the digestible portion of a 

 pound of maize has a heat value to the horse equal to 

 that of rather more than three-quarters of a pound of 

 starch; nearly 10 per cent, of this heat value is used up 

 in the vv^ork of digesting the maize, but from the 

 available energy remaining the horse can put out 542 

 foot-tons of work. On meadow hay, however, although 

 it contains just half the quantity of digestible food, yet 

 so much energy is consumed in digestion that the 

 balance only enables the horse to put out 140 foot-tons 

 of work, or only one-quarter the work that can be done 

 on the maize, though the food yields half as much 

 digestible matter. In the case of straw there is no 

 margin at all left for work. We also see that if the 

 addition of i lb. of maize to a horse's diet enables him 

 to do a certain amount of work, 1-43 lb. of oats or 3 lb. 

 of lucerne hay would be necessary to replace the maize 

 and turn out the same amount of work. Similarly, it was 

 found that when a horse walked I2| miles a day, 20 lb. 



