CHAPTER VII 

 SOME SCIENTIFIC TERMS IN FEEDING 



The Animal as a Machine. Considered as a ma- 

 chine, the animal body needs two classes of food: 

 one, to furnish the materials by which the machine 

 may be constructed and kept in repair; and a sec- 

 ond, or sustaining reserve, to develop heat to keep 

 the body warm and to supply energy for the pro- 

 duction of internal and external work. Water, ash 

 and protein are the essential building materials and 

 the fats and carbohydrates the primary fuel sub- 

 stances. This distinction gives rise to the grouping 

 of feeding stuffs as being either of a building or fuel 

 nature. All individual foods contain both, but in 

 varying proportions ; some are heavy carriers of the 

 first, others of the second, and still others within 

 these two extremes. Food values, therefore, are 

 somewhat dependent upon the manner in which 

 they are classified ; this, of course, being consistent 

 with the nature of their digestible nutrients. 



Nutritive Ratio. A point of some importance in 

 determining the suitability of a feeding stuff as an 

 article of diet is the proportion between the digesti- 

 ble protein and the digestible non-protein organic 

 constituents. This relation is most conveniently 

 termed the nutritive ratio of the food. Simply de- 

 fined, this term means the ratio which exists 

 between the amount of digestible protein to the 

 combined digestible carbohydrates and fat. It is 



54 



