CHAPTER XVIII 



MAINTENANCE RATIONS 



It has already been shown that the demands on the 

 food vary greatly with different individuals or classes 

 of animals according to size and the kind and quantity of 

 production. It is proposed to indicate how rations should 

 be compotmded in order to meet varying conditions and 

 demands for production of various kinds, but as prelim- 

 inary to this an imderstanding should be reached as to 

 what is required to support the producing organism. 



405. Definition of maintenance ration. — ^A main- 

 tenance ration is one supplying the needs of an animal 

 without production of any kind and with no loss of body 

 substance. To be more specific, when an ox doing no 

 work excretes just the quantities of nitrogen and carbon 

 that are contained in the food consumed, he is said to be 

 eating a maintenance ration. The work done by the 

 animal at rest is largely needed in the following direc- 

 tions: The chewing of food and its movement along the 

 intestinal tract; the muscular action of the heart in caus- 

 ing blood circulation; and the metabolic activity of the 

 cells in causing the chemical transformation of the nu- 

 trients. Some work is also done in moving the body and 

 in the effort of standing. The demands upon the food for 

 maintenance purposes are therefore largely for the 

 support of some form of muscular activity. 



406. Character of maintenance ration. — Nine-tenths 

 or more of a maintenance ration may consist of carbo- 



(307) 



