plied simply to 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 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. 



From the scientific point of view, the matter is of even greater 

 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 food with one of its effects, viz., production, 

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

 to appreciate this fact is responsible for many misleading deduc- 

 tions from feeding experiments in the past. It has been quite 

 usual to compare the results of such experiments by computing 

 the ratio of feed consumed to product yielded i. e., either the feed 

 consumed per pound of gain 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, that in a fattening experiment the energy values of 

 two rations (computed according to the table on page 15) and the 

 gains made were as follows : 



First ration Second Ration 



Energy value of feed 9.0 Therms 10.5 Therms 



Daily gain i.o Ibs. 1.5 Ibs. 



Compared in the way just indicated, the feed energy required to 

 produce one pound of gain was 



In the first experiment, 9 Therms 

 In the second experiment, 7 Therms 



or the second ration appears to have been superior to the first by 

 about 29 per cent. If, however, account be taken of the fact that 

 in each experiment a certain portion of the energy value of the 

 feed, 6 Therms, for example, was required simply to maintain the 

 animal, a very different comparison is obtained, viz., 



First ration Second ration 



Energy value of feed 9.0 T. 10.5 T. 



Energy expended in maintenance 6.0 T. 6.0 T. 



Surplus left for production 3.0 T. 4.5 T. 



Daily gain i.o Ib. 1.5 Ib. 



Surplus energy per pound of gain 3.0 T. 3.0 T. 



(5) 



