392 The Feeding of Animals 



THE STUDY OF RATIONS AND DEDUCTION OF STANDARDS 



In studying and comparing different rations, it is not 

 possible to consider all the combinations that can be 

 made of the many foods. It is only practicable to con- 

 sider foods with reference to their varying proportions 

 of constituents. The only portion of these constitu- 

 ents of nutritive value is that which can be digested. 

 Therefore, in compounding rations, we are guided pri- 

 marily by the amount of the digestible nutrients supplied 

 by the food; and feeding standards are for convenience 

 limited to a statement of the assumed requirements in 

 terms of digestible protein, ash, carbohydrates and fat. 

 The bulk of the ration supplying these nutrients must 

 also, of course, fall within certain limits. In the ab- 

 sence of enough specific data calculations must be based 

 on the coefficients of digestibility observed for other 

 animals. These afford safe enough approximations for 

 present use, for the feeding standards must be largely 

 provisional. 



Growth and egg production can only be sustained 

 by the food in excess of that required to support life, 

 although egg production can 'temporarily occur at the 

 partial expense of the body. The amount of food, 

 then, required for simple maintenance puts a limit on 

 one side to an efficient and profitable ration. In the 

 other direction, it is only limited by the capabilities of 

 the individual animal. So the highest possibilities 

 depend altogether on the intelligent judgment, and 

 careful, daily attention of the experienced feeder. In 

 a general way only averages can be considered. 



