2 5 



NUTRITION OF FARM ANIMALS 



liver and muscles. During the first few days of fasting, this 

 store of carbohydrates is also drawn upon, as is indicated by 

 the fact that the respiratory quotient tends to approach unity, 

 while later the amount of glycogen katabolized becomes very 

 small. 



Protein. Balance experiments, however, while confirming 

 the conclusion that the loss of tissue in fasting usually consists 

 chiefly of fat together with some carbohydrates, show that there 

 is also a continual katabolism of body protein and a corre- 

 sponding excretion of urinary nitrogen. While the energy 

 expended by the fasting animal is derived chiefly from the 

 breaking down of non-nitrogenous material, the functional 

 activities of the body necessarily involve the katabolism of a 

 certain minimum amount of protein. 



Ash. Finally, in addition to those groups of substances 

 whose katabolism yields energy to the body, the so-called min- 

 eral elements, or ash, of the body take part in the processes of 

 katabolism and are continuously excreted in the urine of the 

 fasting animal. 



The foregoing facts are well illustrated by Benedict's l inves- 

 tigations upon inanition. The average results of a number of 

 experiments in which men fasted for from two to seven con- 

 secutive days were as follows : - 



TABLE 29. AVERAGE KATABOLISM OF FASTING MEN 



1 The Influence of Inanition on Metabolism ; Carnegie Institution of Washington, 

 Publication No. 77 (1907), pp. 456-464. 



* Omitting one case in which a small gain of glycogen was observed. 



