316 POULTRY CULTURE 



The length of time for a bird to reach the age of full develop- 

 ment, as far as skeleton and muscle is concerned, varies with 

 the care, feed, and breed. If the birds are properly fed the 

 smaller breeds, as those belonging to the Mediterranean — 

 namely, the Leghorn and Minorca — will be sufficiently de- 

 veloped to lay at about five months of age, while the larger 

 breeds, as the Asiatics and American — namely, the Cochins, 

 Plymouth Rocks, and Wyandottes — may not lay till they are 

 six or even seven months old. 



The workers at Cornell have determined by careful observa- 

 tions that a young bird molts four times before growing its 

 permanent adult feathers and does not lay till adult plumage is 

 developed. 



The late molting hen is the heavy layer and it is therefore 

 advisable to select the late molter for breeding. 



S. C. White Leghorn pullets force fed from baby chick to 

 maturity have laid at four months and four days to five months 

 of age. 



In selecting hens for breeding one should take only the heavy 

 layers if increased egg production is desired. An average- 

 sized egg weighs about 2 ounces. Of this, 11 per cent, is shell, 

 32 per cent, is yolk, and 57 per cent, is white. The principal 

 chemical constituents are ash or mineral matter, which con- 

 stitutes 9 per cent.; fat or hydrocarbon, O^fo per cent.; pro- 

 teins or nitrogenous-containing substance, llMo per cent.; 

 water, GSjfo per cent. 



Calcium, or lime-salts, is essential for the formation of the 

 egg-shell. As the feeds commonly fed to poultry do not con- 

 tain sufficient lime, it is necessary to feed shell, as oyster-shell, 

 unless the birds are on range where they have an opportunity 

 to pick up lime. 



Foods consist of three organic compounds as follows: Pro- 

 tein, carbohydrates, and hydrocarbons. Protein contains the 

 following elements — carbon, hydrogen, oxygen, nitrogen, and 

 sulphur. All the nitrogen of the foodstuffs is contained in the 

 protein. The carbohydrates contain three elements — namely, 

 carbon, hydrogen, and oxygen — ^and include the starches, 

 sugars, gums, resins, and other similar substances. 



The third compound, the hydrocarbons, are composed of 



