42 



MAINTENANCE RATIONS OF FARM ANIMALS. 



latiou. therefore, shows the amount of nietabolizable energy of meadow hay 

 which was necessary for the maintenance of the animal : 



Therms. 



Energy of feed 32. 177 



Energy of feces 11. 750 



Energy of urin 1. 945 



Energy of methane 2. 114 



Energy of total excreta ■ 15.809 



Metabolizable energy of ration 16.368 



Metabolizable energy equivalent to gain 3. 602 



Metabolizable energy for maintenance 12. 766 



This method of computing the metabolizable energy necessary for maintenance 

 is obviously the same in principle as that employed in Arinsby and Fries' s 

 experiments, differing only in the fact that the comparison is made on amounts 

 of feed exceeding the maintenance ration. Kellner's results, however, can not 

 be made the basis of a direct computation of the available energy required for 

 maintenance, since it appears probable that a larger percentage of the energy 

 of hay is available below the point of maintenance than is utilized for gain 

 above it. 1 



In two cases (ox B and ox IV) the rations were less than the maintenance 

 ration and the animals lost more or less protein and fat. In computing 

 these experiments Kellner, in accordance with the ideas then generally ac- 

 cepted, simply added the energy equivalent to the loss of tissue to the total 

 metabolizable energy of the feed to obtain the maintenance ration. It is evi- 

 dent, however, from what has subsequently been learned regarding the avail- 

 ability of metabolizable energy, as outlined in the foregoing paragraphs, that 

 if, for example, ox B lost tissue equivalent to 1.498 therms it would have 

 required more than this amount of metabolizable energy in the food to make 

 good the loss, the quantity necessary depending upon the availability of the 

 energy. Of the latter we have no determinations for this particular ration, but 

 for purposes of computing a correction we may, perhaps, assume it to be the 

 same as that found by Armsby and Fries for timothy hay, viz, about 57 per 

 cent. On this assumption the equivalent amount of metabolizable energy which 

 would have had to be supplied to reach the maintenance ration of ox B 

 would have been 1.498^-0.57=2.628 therms, a difference of 1.130 therms. For ox 

 IV the corresponding correction is only 0.740 therm. 



Making these slight changes in Kellner's original figures for these two 

 animals for the sake of uniformity, his results are as follows : 



1 Compare Bulletin 128, Bureau of Animal Industry, p. 59. 



