34 POULTRY FOODS 



this purpose, 1 part of fat is equal to 2 l /i parts of 

 carbohydrates. For this reason, when estimating the 

 heating value of foods, it is customary to multiply the 

 amount of fat in them by 2K in order to express its 

 equivalent in carbohydrates. 



That portion of food which contains nitrogen is 

 known as protein. The lean meat of the fowl and the 

 white of the egg are 'composed largely of this principle. 

 As a source of heat and energy, protein is about equal 

 to the carbohydrates, but animal heat obtained from 

 protein is very expensive. Protein is much more costly 

 than the carbohydrates and fats, and no more of it 

 should be fed to fowls than is absolutely necessary to 

 renew waste, make new growth, and furnish the needed 

 quantity for egg formation. 



That part of food which would be left if the food 

 were burned is called ash, or mineral matter, and it con- 

 tains calcium, magnesium, potassium, sodium, iron, and 

 other elements. When assimilated by fowls, ash enters 

 largely into the composition of bones and the shells of 

 the eggs. There is not enough ash for egg and bone 

 formation in the food usually fed to fowls, and for this 

 reason it is necessary to supply them with such mate- 

 rials as oyster shells, clam shells, limestone grit, etc. 



Foods that contain a large proportion of crude fiber 

 are spoken of as roughage, and those that contain little 

 crude fiber and that are nearly all digestible are 

 known as concentrates. Clover hay is an example of 

 roughage; corn meal is an example of a concentrate. 

 Although of little direct value as a food for poultry, 

 roughage, or crude fiber, is important in a food because 

 in passing through the digestive organs it distends them 

 and serves as an irritant that stimulates their me- 

 chanical action and assists them in digesting their 

 contents. 



When feeding fowls it is always best to have a suffi- 

 cient quantity of ash, fiber, and roughage in their 

 rations to extend the crop and to keep the gizzard 

 actively employed in grinding. During the process of 



