906 



EXPERIMENT STATION RECORD. 



ENERGY REQUIRED FOR MASTICATION AND DIGESTION. 



Iii calculating a ration for production for steers and cows it should 

 be remembered (1) that a portion of the food must be utilized to supply 

 energy for the labor of digestion, the amount of which is not definitely 

 known, and (2) that fermentation takes place in the stomach and large 

 intestines of Herbivora. The value of the latter factor may be calcu- 

 lated from the data furnished by Kiihn and Kellner's experiments at 

 Mockern. It was found that on an average 6.5 to 7 per cent of carbon 

 from digestible crude fiber and nitrogen-free material was excreted as 

 methan. According to Tappeiuer's investigations cellulose adds water 

 when it ferments, 100 gm. yielding 4.7 gm. of methan and 33.6 gm. of 

 carbon dioxid, together with 33.6 gm. of acetic and butyric acid. These 

 acids undergo combustion in the body, but, according to the investiga- 

 tions of Mallerve only 75 per cent of their energy can be utilized. In 

 round numbers, 100 gm. of cellulose, 1.7 gm. of methan, and 33.5 gm. 

 of carbon dioxid contain 11.5 gm., 3.5 gm., and 9.1 gm. of carbon, 

 respectively. In other words, in the example cited a total of 12.6 gm., 

 or 28.3 per cent, of the carbon of digestible starch or cellulose is 

 excreted in the form of gas, owing to the fermentation in the intestinal 

 tract. If so much methan is produced by fermentation that its carbon 

 content equals 6.7 per cent (average of 6.5 and 7 per cent) of the car- 

 bon of the total digestible nitrogen-free material (including crude fiber), 

 it may be assumed that carbon dioxid was also formed in the same pro- 

 portion as in Tappeiuer's investigations; that is, for each 6.7 gm. of 

 carbon of methan 17.4 gm. of carbon of carbon dioxid was produced. 

 Therefore 21.12 per cent (17.4+6.7=24.1) of total starch and nitrogen- 

 free extract has undergone fermentation. These calculations are not 

 exact, since hvdrogen is also formed in the intestinal tract. The amount 

 for Herbivora is not known, but it is so small that the error introduced 

 is insignificant. 



The experiments made by Zuntz and the author with a horse may be 

 cited to show the effect which the digestion of crude fiber exercises 

 upon the consumption of oxygen and the production of carbon dioxid 

 in respiration experiments. The horse excreted 4.7 gm. of methan and 

 0.2 gm. of hydrogen per 100 gm. of digestible crude fiber. 



Effect of digestion of crude fiber on respiration. 



100 gm. of crude fiber contains 

 4.7 gm. of methan contains 



Difference 



33.5 gin. of carbon dioxid contains 



Difference 



Deducting the hydrogen excreted. 



Difference 



Carbon. Hydrogen. 



Grams. 



44.44 



3.53 



Grams. 

 6.18 

 1.18 



40.91 

 9.14 



31.77 



5.00 

 .20 



Oxygen. 



Grams. 

 49.38 



49. 38 

 24.30 



25.02 



25.02 



