INTRODUCTION xv ij 



First, since nutrition involves chemical changes by which 

 feed substances are converted into body substances, there is 

 required some knowledge of the chemical compounds concerned 

 and of their occurrence and proportions in plants and animals. 



Second, the conversion of feed substances into body sub- 

 stances is a function of the living organism and it becomes 

 necessary, therefore, to learn something of the processes by 

 which the body effects these changes or, in other words, to 

 study the physiology of nutrition. 



Third, in order to apply the principles of the chemistry and 

 physiology of nutrition to the practical problems arising in the 

 feeding of farm animals it is requisite to determine quantita- 

 tively the amounts of matter and of energy which are required 

 by different species of animals for their support and for the 

 production of meat, milk or work. 



Fourth, to supply the feed requirements as thus ascertained 

 in the most economical manner demands a knowledge of the 

 available feed resources, both as to the nature and quantity of 

 nutriment which they contain and as to the proportion of this 

 nutriment which can be utilized by the body. 



Accordingly, the general subject of the nutrition of farm ani- 

 mals is treated of under four general heads, viz. : 



Part I, The Materials of Nutrition. 

 Part II, The Processes of Nutrition. 

 Part III, The Feed Requirements. 

 Part IV, The Feed Supply. 



