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 of feed required for this purpose is called the maintenance 

 ration of the particular animal. It is the quantity of feed neces- 

 sary simply to support the animal when doing no work and yield- 

 ing no material product. If an animal receiving exactly a main- 

 tenance ration were subjected to a so-called balance experiment, 

 there would be found 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 

 ash. 



The word maintenance is sometimes used popularly in another 

 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 re- 

 quired simply to sustain life. The feed of the horse or calf would, 

 from this point of view, be regarded as consisting of two portions. 

 One of these is the maintenance ration, which if fed by itself would 

 just support the horse at rest or the calf without growth; the 

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

 work is done or growth made. To recur to the illustration of the 

 factory, the maintenance ration keeps the empty machinery run- 

 ning, while the additional feed furnishes the power necessary to 

 turn out the product. 



SIGNIFICANCE OF THE MAINTENANCE RATION. 



It might seem at first thought that not much importance at- 

 taches to a study of maintenance. The animal kept on a maintenance 

 ration yields no direct economic return and hence simple main- 

 tenance feeding should be avoided, so far as practicable, and when 

 it appears desirable to practice it the observation of the skilled 

 stockman, especially if supplemented by occasional weighings, will 

 usually suffice to determine whether or not the end is being attain- 

 ed. Nevertheless, the subject has significance both for practice and 

 for science. 



A very considerable fraction of the feed actually consumed 

 by farm animals on the average probably fully one-half is ap- 



(4) 



