DYNAMICS 161 



animal of 1000 Ibs. live weight, the corresponding amounts of 

 nutrients would be as before (p. 135),! ^- digestible protein, 

 and 8-3 Ibs. of non-nitrogenous nutrients reckoned as starch. 

 And if we further assume that the animal does 14 million 

 foot-pounds of work per day, the dynamic energy required 

 would be 30 kt. = 8 - o Ibs. of starch. But with such a large 

 addition of non-nitrogenous matter it is necessary also to 

 increase the protein. The amount of non-nitrogenous matter 

 may be correspondingly reduced and the total feeding 

 standard for horses doing hard work would therefore be as 

 follows : 



Digestible nutrients. 



Protein. "Starch." 



Ibs. Ibs, 



For maintenance 075 8*3 



,, work i-oo 67 



Feeding standard l . . 175 15*0 



This method of stating the requirements of working horses 

 is open to very serious objection. The nutrients of the main- 

 tenance ration correspond to the total available thermic energy 

 of the food, and those of the special food for work correspond 

 to the dynamic energy. Confusion must result if these two 

 are added together. When both are expressed in terms of 

 equivalent amounts of starch or other nutrient, the difficulty is 

 only disguised, not overcome. Attempts have been made to 

 solve the problem by counting only the dynamic energy of 

 both portions of the food which may then be reckoned as 

 starch. This method, however, is a highly artificial one. It 

 must either involve the assumption that the maintenance 

 portion of the ration is of a certain constant degree of digesti- 

 bility ; or it must be accompanied by a statement of the 

 amount of total organic matter. In any case, the feeding 

 standard, when expressed in terms of total dynamic energy or 



1 Kellner's estimate is 2 '2 Ibs. of protein and 157 Ibs. of non- 

 nitrogenous nutrients (reckoned as starch); that of Wolff is 2-3 Ibs. of 

 protein and 14*5 Ibs. of non-nitrogenous nutrients (reckoned as starch). 

 The differences are probably to be attributed to the difference in the 

 estimates of the amount of work done. 



M 



