PRINCIPLES OF STOCK FEEDING 187 



Professor Brooks of Massachusetts well says: "Some 

 knowledge of the composition of animal products and 

 of foods; some knowledge of the laws of nutrition, and 

 of the facts discovered by scientific men regarding the 

 most economical production of meat, of fat, of milk, 

 and work, will help even the best practical feeder. Such 

 knowledge will not render the exercise of the observing 

 faculties and of the judgment the less important. It 

 will rather sharpen the one and broaden the other." 



Chemistry of Stock Feeding. — In an attempt to dis- 

 cover principles of stock feeding, investigators have 

 given much attention to the chemical problems, neg- 

 lecting to some extent, perhaps, the physical and the 

 physiological factors involved. It is a pardonable over- 

 sight, since investigations tending to throw light upon 

 the subject should begin with a study of the chemical 

 substances necessary for the development of plant and 

 animal life. The existence of our farm animals is de- 

 pendent upon plant life. There must, therefore, be 

 certain elements or compounds in the plant that con- 

 tribute to the upbuilding of animal tissues. 



Of the eighty-one recognized chemical elements which 

 in their infinite combinations form all organic and inor- 

 ganic substances, only fifteen are involved in the life of 

 agricultural plants, viz., calcium, carbon, chlorine, fluo- 

 rine, hydrogen, iron, magnesium, manganese, nitrogen, 

 oxygen, potassium, phosphorus, silicon, sodium, and 

 sulphur. 



In making application of the chemistry of plant and 

 animal bodies to the subject of stock feeding, it is seldom 

 necessary to deal directly with these elements, but rather 

 with certain compounds made up through various combi- 

 nations of these elements. These classes of compounds 

 are practically the same in plant and animal bodies and 

 are usually referred to as ash, crude fiber, fat, nitrogen- 

 free extract, crude protein, and water. The percentages 

 of crude fiber and nitrogen-free extract are commonly 

 grouped together and referred to as carbohydrates. 



