THE COMPOUNDING OF RATIONS 361 



as well, the feeder may compute a l)alaneed ration, making 

 due allowauce for the \'itamins. 



There are two methods of calculating a feeding standard. 

 One is by means of digestion trials and the other by dietary 

 trials. Theoretically, the proper method is by means of 

 digestion experiments. While this is possible for maintenance 

 standards, it is not practicable for a standard for hens in 

 full laying or for growing young stock. This is because the 

 necessary technique employed in carrying on digestion experi- 

 ments W'ould greatly interfere with egg production or growth 

 and so would defeat their purjjose. 



The method using dietary trials is the one to which jwultry 

 feeders must look for the present. By this method the effi- 

 ciency of different rations for a given purpose is compared 

 and the amounts and proportions of the digestible nutrients 

 in the most efficient rations may then be taken as a standard. 



The most complete standards to be had at present are 

 those compiled by W. P. Wheeler at the New York Experi- 

 ment Station. Unfortunately in the absence of sjjecific 

 data for poultry his calculations were of necessity based on 

 coefficients of digestibility obser\'ed for other animals. These 

 are therefore only approxinuitions to a true standard. It will 

 remain impossible to comjiile a true standard until very much 

 more work has Ijeen done upon the establishing of the diges- 

 tion coefficients of all the common poultry feeds, than has 

 been done up to the present time. In the meantime the 

 Wheeler standards will continue to be of great service in 

 pointing toward the rational feeding of poultry. 



Maintenance Standard. — A maintenance ration is one that 

 furnishes a sufficiency of each and all of the several nutrients, 

 but no more than is required to maintain a given bird that 

 is not laying and is as nearly at rest as possible, so that it will 

 not gain or lose in weight. 



Because of the pronounced vitality, the very rapid breath- 

 ing, the high body temperature, and the fact that the 

 smaller the animal the greater is the surface area relative to 

 bulk, and the greater the relative heat production, it might 

 be expected that poidtry would demand a relatively high 

 consumption of carbohydrate. /\.s a matter of fact, while 



