Dec. 1, 1925 
The Maintenance Requirement of Dry Cows 
1063 
This loss of carbon unaccompanied by nitrogen may result from 
two sources, viz, from a continuation of the intestinal fermentation 
after the feces have been voided, and from the breaking up of the 
nonnitrogenous compounds in the urine. That both processes con¬ 
tribute to this excess of carbon dioxide seems probable. However, 
the present state of the writers’ knowledge of the compounds in¬ 
volved in the decomposition of the urine is insufficient to serve as 
the basis for the correction of its energy, and this has not been 
attempted. Neither has the energy of the urine been corrected for 
the free ammonia and free carbon dioxide present. 
When the sources of the carbon dioxide lost during the drying of 
the mixed feces and urine, in excess of that coming from the nitrog¬ 
enous compounds of the urine, are considered, to wit, the crude 
fiber and the nitrogen-free extract of the dung, the writers are im¬ 
pressed with the possibility of extensive error. Soon after the mix¬ 
ture is placed in the drying closet a thick scum forms over the sur¬ 
face, this scum preventing rapid drying and at the same time main¬ 
taining in the interior of the mass conditions favorable for the con¬ 
tinuance of digestive cleavage and for the development of bacteria 
with the resultant formation of methane and carbon dioxide. This 
condition was not recognized early enough in this series of experi¬ 
ments to have permitted of direct determinations of the amounts of 
the gases lost. However, in all experiments following 221E the total 
carbon was determined by direct combustion of the fresh material, 
and this, in conjunction with the total nitrogen as determined in the 
fresh substance by Konig’s method, furnishes sufficient data to make 
possible a computation of the energy loss due to the aforementioned 
factors. 
It is apparent, then, that the carbon lost on drying the mixed feces 
and urine must be divided into three parts, in so far as its relation 
to the corresponding energy loss is concerned: (1) That portion which 
is combined with nitrogen and is accounted for through the use of 
Rubner’s factor of 5.45 Cal. per gram of nitrogen lost on drying; 
(2) that portion which is present m solution as part of the system 
NH 3 .C0 2 .H 2 0 (this is to some extent compensated for by the fact 
that a portion of the NH 3 present in this system has been included 
in the total nitrogen lost on drying, its carbon equivalent thus being 
taken into account, as will later appear); (3) the residuum of carbon 
considered as originating in the fermentation of the nonnitrogenous 
material. 
Since this fermentation simulates intestinal fermentation, not only 
carbon dioxide but also methane is produced. This latter the writ¬ 
ers have been unable to determine quantitatively. However, in view 
of the relatively small difference between the heats of combustion 
of crude fiber and nitrogen-free extract, the writers feel justified in 
computing the amount of energy lost through this external fermen¬ 
tation from the carbon dioxide produced and the energy equivalent 
of starch, as representing nitrogen-free extract generally. 
Since in experiment 22ID the carbon was not determined in the 
fresh dung and urine mixture, it was necessary to compute the 
correction for this experiment on the basis of average figures. 
The data upon which this computation is based are indicated in 
Table VIII. 
