392 



NUTRITION OF FARM ANIMALS 



As explained in Chapters VIII and XVII (366, 759), Rubner's 

 "specific dynamic action" is synonymous with the energy expendi- 

 ture caused by the consumption of feed, and if it be subtracted from 

 the metabolizable energy the remainder is the net energy. The per- 

 centage utilization is of course the net energy divided by the metab- 

 olizable energy. 



Estimated in this way, the percentage utilization would be 

 as shown in the first column of the following table, the second 

 and third columns of which show the utilization as computed 

 by the writer both with and without a 10 per cent addition to 

 the fasting katabolism as estimated from the data on mature 

 animals. 



TABLE 89. ESTIMATED UTILIZATION OF METABOLIZABLE ENERGY OF 



MILK 



While it is clear that no final conclusions can be based upon 

 small differences between figures obtained as these have been, 

 it seems suggestive, nevertheless, that the actual experiments 

 with growing animals show a lower average utilization than 

 would be expected from Rubner's results upon mature animals. 

 Moreover, Wilson's results are apparently lower than those 

 which may be computed from Meissl's and Kornauth and 

 Arche's respiration experiments upon mature swine consuming 

 grain (757). Certainly these comparisons afford little sup- 

 port to the notion that the utilization of energy in the physio- 

 logical sense by young animals is much higher than that by 

 mature animals. 



