268 NUTRITION OF FARM ANIMALS 



done or growth made. To recur to the illustration of the fac- 

 tory, the maintenance ration keeps the empty machinery 

 running, while the additional feed furnishes the power neces- 

 sary to turn out the finished product. 



359. Significance of the maintenance ration in practice. 

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

 taches to a determination of the maintenance ration. The 

 animal kept on such a ration yields no direct economic return 

 and hence simple maintenance feeding is to be avoided, so far 

 as possible, while if it appears desirable to practice it the ob- 

 servation of the skilled stockman, especially if supplemented 

 by occasional weighings, will usually suffice to determine whether 

 or not the end is being attained. Nevertheless, the subject has 

 much 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 required simply for maintenance. But if half of the farmer's 

 feed bill is expended for maintenance, it is clearly important 

 for him to know something of the laws of maintenance, how 

 its requirements vary as between different animals, how they 

 are affected by the conditions under which animals are kept, 

 how different feeding stuffs compare in value for maintenance, 

 etc., as well as to understand the principles governing the 

 production of meat, milk, or work from the other half of his 

 feed. 



360. Bearing on interpretation of feeding experiments. 

 From the point of view of the experimenter a knowledge of 

 the maintenance requirement is likewise of great importance. 

 In any rational study of the laws of nutrition, it is plainly 

 inadmissible to attempt to establish general principles by a 

 comparison of the feed with one of its effects, viz., production, 

 while ignoring entirely its other effect, viz., maintenance. 

 Failure to appreciate this fact is responsible for many mislead- 

 ing deductions from feeding experiments in the past. 



It has been quite usual to compare the results of such experi- 

 ments by computing the ratio of feed consumed to product 

 yielded i.e., either the feed consumed per pound of gain 

 made or the gain produced per pound of feed consumed. Such 

 a comparison, however, may give an entirely distorted idea of 

 the real teachings of an experiment. Suppose, for example, 



