FEEDS AND FEEDING 



PART I 

 PLANT GROWTH AND ANIMAL NUTRITION 



CHAPTER I 



THE PLANT; HOW IT GROWS AND ELABORATES FOOD 



FOR ANIMALS 



I. PLANT GROWTH 



All food for animals, with the exception of air, water, and salt, is sup- 

 plied either directly or indirectly by plants. .To understand the feeding 

 of live stock, one should therefore know how plants grow and build this 

 food and of what it consists. 



7. The food of plants. Both plants and animals are composed of a 

 great many substances or compounds yet all are made up of a relatively 

 small number of chemical elements. Indeed, of the 80 or more elements 

 known to the chemist, only 14 are commonly present in plants. Of these, 

 at least 10 are absolutely necessary for plant growth. These are : carbon, 

 hydrogen, oxygen, nitrogen, sulfur, phosphorus, potassium, calcium, mag- 

 nesium and iron. Sodium, silicon, chlorin, and manganese are usually 

 found in plants and may be essential to their growth. Iodine also is 

 present in some plants. Except in the two instances which will be noted 

 later, plants cannot use for food the uncombined elements, such as metal- 

 lic iron or carbon in the form of charcoal, but they are nourished by 

 water, carbon dioxid (carbonic acid gas), and mineral salts all of which 

 are compounds containing the elements in chemical combination. 



Water, composed of hydrogen and oxygen, is the largest single com- 

 ponent of plants; forming from 75 to 90 per ct. of their fresh weight. It 

 serves a double purpose in plants. Some of it is used as food, while the 

 rest serves as the carrier of plant food. Only when it is dissolved in the 

 watery sap can plant food be taken from the soil by the roots or be car- 

 ried from one part of the plant to another. The plant obtains practically 

 all its water from the soil thru its roots, only a small amount being taken 

 from the air by the leaves. Soil water, absorbed by the roots, enters the 

 cells of which the plant is composed and passes onward and upward thru 

 the stem, moved by capillarity and sap currents, eventually reaching 



