MAINTENANCE THE ENERGY REQUIREMENTS 269 



that in a fattening experiment the quantities of two different 

 rations consumed and the gains made were as follows : 



FIRST RATION SECOND RATION 



Feed eaten 18.0 Ib. 21.0 Ib. 



Daily gain i.o Ib. 1.5 Ib. 



Compared in the way just indicated, the feed required to pro- 

 duce one pound of gain was 18 pounds and 14 pounds respectively, 

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

 by about 29 per cent. If, however, it was found that in each 

 case 12 pounds of the feed were required simply to maintain 

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



FIRST SECOND 



RATION RATION 



Lb. Lb. 



Feed eaten , 18.0 21.0 



Expended in maintenance 12.0 12.0 



Surplus left for production . 6.0 9.0 



Daily gain i.o 1.5 



Surplus feed per pound of gain , 6.0 6.0 



The real value of the two rations per pound is thus shown to 

 have been the same. The economic advantage on the side of 

 the second was not due to any higher nutritive value but 

 simply to the fact that more of it was eaten. Similarly, if the 

 foregoing results be supposed to have been obtained, not with 

 two different rations but with two different animals on the 

 same kind of feed, the experiment does not show that the second 

 animal digested or assimilated his feed any more efficiently than 

 the first, but simply demonstrates the economic advantage of 

 a larger consumption of feed. It scarcely need be added that 

 the same principle applies to all cases of productive feeding, as 

 has recently been shown in a very striking manner by Eckles l 

 in experiments upon dairy cows. Clearly, a knowledge of 

 the maintenance ration is essential to any logical interpretation 

 of experimental results. 



361. Requirements for maintenance. Corresponding to 

 the dual function of the feed (263) as a source of energy for the 

 bodily activities and of specific substances necessary for the 

 growth, maintenance and repair of the tissues, the maintenance 



1 Mo. Exp. Sta., Research Bui. No. 2. 



