196 THE FEEDING OF ANIMALS 



nutrients which are consumed, that is, burned as fuel, 

 increases as the ration increases above what is needed 

 for maintenance, and inversely the proportion of the 

 nutrients stored in the body as flesh and fat undoubtedly 

 is less the greater the quantity fed is in excess of the 

 demands for maintenance. A large excess over mainte- 

 nance is relatively less efficient than a small one in the 

 production of flesh or milk. There comes a point where 

 additional food produces no additional gain, but only 

 additional consumption. The age of the growing animal 

 and the condition of a fattening animal also modify the 

 efficiency of the food for production purposes, as does 

 individuality, and with a cow the stage in the period of 

 lactation. With all these variations no averages are pos- 

 sible which express with any definiteness fixed production 

 values for the different nutrients. 



