CHAPTER VIII 

 MAINTENANCE THE ENERGY REQUIREMENTS 



358. Definition of maintenance. Feed is supplied to farm 

 animals either that they may yield products useful to man as 

 materials for human food and clothing or that they may serve 

 him by the performance of mechanical work. 



But much as a factory must first be supplied with enough 

 power to keep in motion the shafting, belting and machinery 

 in general before any product can be turned out, so the animal 

 mechanism must be provided with sufficient feed to maintain 

 the processes essential to life before any continued production 

 is possible. The amount required for this purpose is called 

 the maintenance ration of the particular animal. It is the 

 quantity necessary simply to support the animal when doing 

 no work and yielding no material product. A balance experi- 

 ment with an animal receiving precisely a maintenance ration 

 would reveal an exact equality between income and outgo of 

 ash, nitrogen, carbon, hydrogen and energy, showing that the 

 body was neither gaining nor losing protein, fat, carbohydrates 

 nor mineral elements. From this point of view, maintenance 

 might be characterized as a state of labile equilibrium between 

 the anabolic and katabolic processes of metabolism (203). 



The word maintenance is sometimes used popularly in an- 

 other sense to signify the total amount of feed required, for 

 example, by a horse in order to perform his daily work or by a 

 calf in order to make a normal growth. It is important to grasp 

 the idea that, in its technical sense, the maintenance ration 

 means the minimum required simply to maintain life. The 

 total feed of the horse or calf would, from this point of view, be 

 regarded as consisting of two portions ; one of them the main- 

 tenance ration, which if fed by itself would just support the 

 horse at rest or the calf without growth, and the other the 

 productive portion of the ration, by means of which work is 



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