2 PRINCIPLES OF FEEDING FARM ANIMALS 



as iodine, fluorine, silicon, aluminium, copper, arsenic, and 

 manganese, often occur in small amounts in plant and animal 

 life, but they are not of sufficient importance in this con- 

 nection to warrant their further mention. 



Compounds. — Although vegetable and animal substances 

 consist primarily of chemical elements, these elements, with 

 the exception of small amounts of oxygen and nitrogen, do 

 not exist in the plant or animal in the free, elemental state, 

 but they occur in combination with one another to form com- 

 pounds, such as sugar, starch, fat, and water. The compounds 

 which occur in plant and animal fife are large in number and 

 vary considerably in their chemical composition, their proper- 

 ties, and their nutritive values. In fact, these compounds are 

 so numerous and varied that the chemist has attempted to 

 simpHfy their discussion by dividing them into five classes, put- 

 ting all compounds of similar composition, properties, and nu- 

 tritive value into the same class. These classes are as follows : 

 (1) water, (2) mineral matter or ash, (3) crude protein, (4) car- 

 bohydrates, and (5) fats. The first two classes are incombusti- 

 ble, and are called inorganic compounds, while the last three 

 classes are combustible, and are called organic compounds. 



Nutrients. — These classes of compounds often are spoken 

 of as nutrients. Although the term is used rather loosely, 

 a nutrient may be defined as any feed constituent or group of 

 constituents of the same general chemical composition that 

 is capable of Hberating energy or serving for the production 

 of tissue in the animal body. In other words, it is any feed 

 constituent or group of constituents which may aid in the 

 support of animal fife. Thus water, mineral matter, crude 

 protein, carbohydrates, and fats are usually regarded as 

 the nutrients of feedingstuffs. 



