FEEDING OF POULTRY 409 



of the different nutrients of the food and a discussion of 

 their functions will be found elsewhere in this volume. 

 The facts apply to the feeding of poultry as well as to 

 that of other animals. 



It appears from present knowledge that protein 

 derived from animal sources is more efficient for certain 

 uses, particularly the feeding of ducklings, than that 

 derived from vegetable foods. Previous mention has been 

 made of experiments at the New York Experiment Sta- 

 tion, the results of which accord with this assumption. 

 The rations which contained animal food proved much 

 more efficient than those of vegetable origin, the latter 

 having, according to the ordinary methods of estimation, 

 the same nutritive value as the former. 



498. Ash constituents important for egg production. 

 It seems probable that the ash constituents have some- 

 times not been sufficiently considered in feeding. While 

 the importance of the mineral nutrients can be largely 

 overlooked without serious practical disadvantage when 

 feeding some animals for certain purposes, it must be 

 given consideration when feeding domestic fowls. While 

 in milk, for instance, about 5 per cent of the dry matter 

 is ash, in eggs over 35 per cent of the dry matter is repre- 

 sented by the mineral constituents. 



The shell of the egg, which represents about 11 per 

 cent of the fresh egg, consists almost entirely of carbonate 

 of lime. Most grain foods, which naturally constitute the 

 bulk of ordinary rations, contain little mineral matter 

 and the amount of lime is notably low. For simply sup- 

 plying the deficiency of material for the egg shell, car- 

 bonate of lime in the form of oyster shell can be used. 

 This was shown in experiments at the New York Experi- 

 ment Station made with laying hens after they were 



