THE PRODUCTION VALUES OF FEEDING STUFFS 647 



show much smaller differences between the observed and com- 

 puted results, the fermentation losses in particular being notably 

 less with swine than with cattle or sheep (745). 



TABLE 189. COMPARISON OF METABOLIZABLE ENERGY PER POUND 



Kellner has attempted to secure factors for cattle similar to 

 those of Rubner for men and carnivora by means of experiments 

 in which approximately pure nutrients (starch, sugar, oil, gluten) 

 were added to a basal ration. In the case of starch, for ex- 

 ample, the increase in the amount of nitrogen-free extract di- 

 gested was compared with the increase in the total metaboliz- 

 able energy of the ration, the losses of energy in feces, urine 

 and methane being determined with the aid of a respiration ap- 

 paratus by the method of indirect calorimetry (329). The re- 

 sults are corrected for the effects of the starch upon the digest- 

 ibility of the several nutrients of the basal ration and upon 

 the losses from the latter in urine and methane, i.e., the real 

 metabolizable energy is computed. A few similar deermina- 

 tions on other species have also been reported. 



In an earlier publication 1 the writer has discussed in con- 

 siderable detail the recorded experiments regarding the metab- 

 olizable energy of the nutrients digested by farm animals 

 with the results summarized in the following table. To the 

 extent to which satisfactory factors can be selected, this table 

 may be used to compute the metabolizable energy of feeding 

 stuffs or rations whose digestibility is known, but it should be 

 noted that the results will include no allowance for the secondary 

 effects of the feed on the digestive processes and will prob- 

 ably be higher than the " apparent " metabolizable energy 

 obtained by direct experiment. 



1 Principles of Animal Nutrition, pp. 302-335. 



