450 



Journal of Agricultural Research 



Vol. Ill, No. 6 



to judge the full significance of Zuntz's results, but they should at least 

 serve to correct the notion, more or less subconsciously held by not a 

 few, of digestion as a perfectly definite process and of a digestion coeffi- 

 cient as a sort of chemical constant. On the other hand, however, it 

 is easy to overestimate the importance of these variations in the digestive 

 process in their bearing upon estimates of the values of feeding stuffs. 

 On the whole, they appear to be of far less significance than other factors 

 to be considered later. 



ESTIMATION OF METABOUZABLE ENERGY 

 FROM METABOLISM EXPERIMENTS 



The losses of chemical energy in feces and urine are readily determined 

 by means of the ordinary metabolism experiment, but the determination 

 of the losses in the combustible gases requires special and somewhat 

 costly apparatus. A number of experimenters have therefore attempted 

 to estimate the amounts of these gases produced, usually from the 

 amounts of carbohydrates (crude fiber and nitrogen-free extract) digested, 

 using, as a rule, the average factor derived from Kellner's investigations 

 (26, p. 420) — viz, 4.2 parts of CH4 per 100 parts of digested carbohydrates. 



Our experiments have yielded somewhat higher figures, as shown in 

 Table VI, giving the maximum, minimum, and average results for each 

 feeding stuff or mixture. 



T.\BLE VI. — Quantity of methane per 100 gm. of digestible carbohydrates 



Feeding stuff. 



Num- 

 ber of 

 experi- 

 ments. 



Quantity of methane. 



Ma.^i- 

 nium. 



Mini- 

 mum. 



Aver- 

 age. 



Timothy hay 



Clover hay 



Mixed hay 



Alfalfa hay 



Maize stover 



Average 



Maize meal and clover hay 



Wheat bran and timothy hay 



Grain mixture No. i and timothy hay. . 

 Grain mixture No. 2 and alfalfa hay ... 



Maize meal and mixed hay 



Hominy chop and mixed hay 



Average 



Average of author's experiments. 

 Average of Kellner 's experiments 



5 

 6 



17 

 3 



43 



65 



44 



4-3 

 4.8 



4.7 

 3-8 

 4.2 

 4-4 



3-S 

 2.9 



5- I 

 5-2 

 5-8 

 5-3 

 4.8 



5- 2 

 5-2 

 5-3 

 5-5 

 4.7 

 5-0 



5-5 

 5-5 



4.6 

 4.6 



5- I 

 4.8 



4-7 



4.8 



4.8 

 4.9 

 5-0 

 4-S 

 4-S 

 4-7 



4-7 



4.8 

 4.2 



