CHAPTER XIII 

 FEEDS AND FEEDING 



Source. — We have learned that the carbon dioxide 

 exhaled by animals is used by growing plants; that this 

 carbon dioxide in the air unites with water and other ele- 

 ments taken by the roots of the plants from the soil, and 

 forms starch and other compounds of which plants are com- 

 posed. The heat or energy given off by the sun is used to 

 build up these compounds in the plant. Animals are de- 

 pendent, then, upon plants for all their feed. 



Requirement. — The act of living involves energy and 

 the necessary consumption of nourishment, as a fuel, to 

 supply the vital force. As the heart works to send supplies 

 to the various parts of the body, it must itself undergo a 

 constant repair, and hence it has its own blood vessels. 

 To think and to walk are at the expense of energy created 

 by the consumption of parts of the body. To run requires 

 more energy and, therefore, causes more waste than to 

 walk. So, then, the harder animals work the more nourish- 

 ment, or feed, they must have. 



How Made Available. — When plants, such as grass, hay 

 or grain, are eaten by animals and digested, the compounds 

 they contain are broken down and used by the animal body, 

 and the energy required to build up the compounds in the 

 plants furnishes energy to the animal. 



Selection. — By chemical analysis men have been able 

 to determine the exact constituent elements of plants, that 

 is, how much hydrogen, oxygen, nitrogen, carbon, phos- 

 phorus, etc., has entered into their composition. They 

 know, also, the proportion of these elements that is found 

 in animal bodies. With these facts before us, therefore, 

 it is easy to select the proper feeds for each kind of animal 

 according to its composition and peculiar physical adapt- 

 ability to get the most benefit from this or that kind of 

 feed. Different kinds of animals, and animals doing dif- 

 ferent classes and amounts of work, require different kinds 



