FEEDING OF POULTRY 411 



always be freely supplied. Clean, sharp sand is useful 

 for the very young birds and is quite generally considered 

 an essential part of all mixtures fed to ducklings. Good 

 results accompany its free use. 



501. Feeding standards for fowls. 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 consider foods with reference to 

 their varying proportions of constituents. The only 

 portion of these constituents of nutritive value is that 

 which can be digested. Therefore, in compounding 

 rations, we are guided primarily 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 pro- 

 tein, ash, carbohydrates, and fat. The bulk of the ration 

 supplying these nutrients must also, of course, fall within 

 certain limits. In the absence of enough specific data, 

 calculations must be based on the coefficients of digesti- 

 bility 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 ani- 

 mal. 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. 



