Investigations Concerning the Horse. 



261 



used up in the work of mastication and digestion. By subtracting 

 the energy thus expended from the total energy furnished by the 

 digestible portion of any feed its net nutritive value may be found. 

 With the resting animal the energy of the food expended in mastica- 

 tion and digestion serves, within certain limits, to maintain the tem- 

 perature of the body after its conversion into heat; but for pro- 

 ducing external work, only that net portion of the digestible nutri- 

 ents which remain after the work of mastication and digestion has 

 been performed is of value. (71) 



According to Zuntz,^ the 1100-lb. horse when moving on a prac- 

 tically level road will produce about 864.4 ft.-tons of work in draft 

 for each pound of net nutrients consumed in addition to the main- 

 tenance requirement. In accordance with such conclusion the fol- 

 lowing table shows the possible work various feeding stuffs will yield 

 when fed to the horse in excess of the amount required for its main- 

 tenance : 



The table shows that after supplying the horse with sufficient feed 

 to maintain the body when at rest, each additional pound of corn 

 supplied, up to the capacity of the animal, will furnish energy suf- 

 ficient to produce 607.7 ft.-tons of external work, or enough to lift 

 a weight of one ton 607.7 ft. against the pull of gravity. Because 

 of its high per cent of digestible nutrients and its low content of 

 fiber, Indian corn is the most potential of all the given feeds for the 

 l^roduction of work. 



^ Landw. Jabrb. 27, 1898, Sup. Ill, p. 431. 



