Part V 

 THE FEEDS 



CHAPTER XXIII 



THE COMPOSITION OF FEEDS AND THEIR MANURIAL 



VALUE 



The feeding of animals consists of supplying them with certain 

 chemical substances called nutrients which their bodies require 

 for life and growth and for the manufacture of some product such 

 as milk. Thus, the value of a given feed rests on its content of 

 these nutrients. The chemical substances which we will consider 

 in this connection are: water, proteins, carbohydrates, fats, and 

 mineral elements. 



314. Water. Dry matter.— Water forms about 50 per cent 

 of the live weight of the animal body. All feeds contain some 

 water but we are primarily interested in the part which is not 

 water, which is called dry matter. All the other nutrients are parts 

 of the dry matter and thus the more water the less the content of 

 these other nutrients in the feed. 



315. Proteins. — These are complex compounds containing 

 nitrogen. In the body the muscles, the organs, the skin and the 

 hair consist almost entirely of proteins. Thus, it is easy to under- 

 stand that the animal requires large amounts of these compounds 

 in its feed both for growth and for replacing worn out body tissues. 

 Similarly, milk contains a high percentage of proteins and there- 

 fore the dairy cow needs a liberal supply for milk production. 



Everyone is familiar with the term, crude protein, used in 

 expressing the analysis of feeds. Actually there are several different 

 kinds of proteins in a feed and feeds differ among themselves in 

 this respect. A given amount of protein in one feed may cause 

 more growth or produce more milk than the same amount in 



189 



