268 POULTRY CULTURE 



the supply. The conditions ideal for laying on fat are found 

 to be as in the case of finishing birds, where exercise is restricted 

 and proper diet given. 



Mineral Requirements of Fowls. — The mineral substances 

 which enter into the composition of fowls constitute the ash. 

 Certain minerals are required for secretion and function. 

 The force feeding of fowls for growth into broilers, as well as in 

 egg production as applied to mature hens, both call for a higher 

 percentage of mineral nutrients in feed stuffs than was neces- 

 sary under the old system of less intense production. Minerals 

 are also required for growth and repair. 



Use of Mineral in the Body. — The importance of mineral 

 salts in the vital processes of the animal cell lies almost entirely 

 in their physical or physico-chemical properties. The chem- 

 ical reaction in the body which constitutes the physical basis 

 of life takes place between substances in solution, and it is 

 by means of the electrical charges carried by the particles in 

 solution that reactions are brought about. 



The mineral elements in the body are most of them strongly 

 acid or basic, and their compounds have a tendency to become 

 exceedingly active when in dilute solution; also the small size 

 of the molecules of their simpler compounds allows them to 

 pass freely through cell membranes that are impenetrable to 

 many of the larger molecules of the complex compounds. 

 The mineral substances of fowls' tissues exist not merely in 

 solution but partly in firm combination with the organic 

 constituents. These mineral substances render chemically 

 active the large and inert organic complexes to which they are 

 bound. 



Kinds of Minerals. — The minerals of the body occur in 

 the form of calcium oxide, inorganic phosphates, lecithins, 

 phosphoproteins. In the inorganic phosphates phosphorus 

 is present as salts of the mineral bases, calcium, magnesium, 

 potassium, and iron. Sodium occurs principally as sodium 

 chloride and to a less extent as sodium phosphate and sodium 

 carbonate. Potassium is present mostly as salts of mineral 

 acids. Magnesium usually combines with phosphate forming 

 magnesium phosphate; sulphur in combination with proteid 



