THE FEEDING OF POULTRY 365 



their own rations, full-fed poultry develop faster and better 

 individually, but at the cost of shorter life .and reduction of 

 vitality in the offspring. The poultryman's object is to get 

 as much as possible out of the birds in the shortest possible 

 time; that is, to market as soon as possible those destined 

 primarily for the table, and to keep laying and breeding 

 poultry only as long as they are highly productive. He 

 forces by feeding, but not (intentionally) to the danger 

 point, just as a careful horseman often drives his horse much 

 faster and farther than the horse would go of its own accord, 

 yet avoids over-driving." 



The use of mineral foods by fowls is even more important 

 than with farm animals. Growth in proportion is really 

 much greater with the fed fowl than the four-footed animal, 

 while the production of eggs requires a considerable amount 

 of mineral matter. The common supply of food does not 

 always furnish enough of the mineral substances, and espe- 

 cially lime, to meet the needs of the fowl. This is particu- 

 larly true of the laying hen. Consequently some other 

 material must be added, and green ground or broken burned 

 bone, granulated dry bone, and finely broken stone are 

 commonly used to serve this need. Ground or finely broken 

 oyster shells have always been popular for laying hens. As 

 to the exact needs of the body for mineral food, we do not 

 know, but it may be assumed, as based on practice anji the 

 result secured with farm animals, that the mineral substances 

 play a part in nutrition. Robinson, however, believes that 

 in "good feeding of mixed rations," under range conditions 

 young birds get all the mineral elements they require, and 

 adult birds all they need, except for producing egg shells. 

 He does not think grit is necessary, and since 1902 has fed 

 none to poultry, except in the first feeds of young ducks and 



