PART I 



PRINCIPLES OF FEEDING FARM ANIMALS 



CHAPTEK I 

 THE COMPOSITION OF FEEDING STUFFS 



The feeding stuffs used for the nutrition of farm animals are, 

 as a general rule, of vegetable origin. They are either farm crops 

 grown especially for this purpose, or are by-products from manu- 

 facturing processes in which farm crops furnish the raw materials. 

 It will be well, therefore, to examine into the composition of plants 

 at the outset, in order that the discussions given in the following 

 pages relative to the feeding of farm animals and problems con- 

 nected therewith may be clearly understood. 



Chemical Elements. — Plants are composed of an immense 

 number of different compounds ; some of these are present in large 

 proportions, others in only small amounts. When these compounds 

 are separated into their ultimate constituents we find that they con- 

 tain a relatively small number of substances which, according to 

 our present knowledge, cannot be further subdivided. These sub- 

 stances are known as elements. About a dozen of the elements are 

 absolutely necessary to plant life, and no plant can grow in the 

 absence of one or more of them. These so-called essential elements 

 are: 



Carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potas- 

 sium, calcium, magnesium, iron, fluorin, and iodin. 



A few other elements may not be essential to plant growth, but 

 are always present in plants. These are : 



Sodium, chlorin, silicon, and manganese. 



The first group of elements, in fact the first six of them, make 

 up the bulk of all plant materials ; over 95 per cent of the weight 

 of most plants and feeding stuffs is composed of these few elements. 

 But the other essential elements, although present in small amounts, 

 are equally important, since plants cannot grow to maturity if any 

 of them be lacking in the soil or not available to the plant. 



Groups of Components in Feeds. — The elements given in the 

 preceding paragraph are present in plants in chemical combinations 

 with each other, forming in some cases very complex substances 



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