312 PRINCIPLES OF ANIMAL NUTRITION. 
| : Basal Ration 
Basal Ration, 
aged Ration. |“ Giaten 
Ox: Bissccngar we ene 2.94 2.96 
9 AB Saag Senco eiion Seine 2.94 2.82 
OCS ace cuca acme bees 2.71 2.41 
OW TD: Joi stg tiagpeane iin nae 2.75 2.71 
HONS ete evew § sae as 2.87 3.19 
Average ........... 2.84 2.8 
Had the large quantities of digestible protein added to the basal 
rations produced any material amount of methane, that fact must 
have been reflected in the above percentages. This method of 
comparison takes into account the probable effect of the carbo- 
hydrates of the wheat gluten in increasing the production of 
methane, and the substantial agreement of the results with and 
without protein leads to the same conclusion as the preceding 
data. It seems fair to presume that this conclusion applies to 
protein in general, although a strict demonstration of it, especially 
for coarse fodders, would have its difficulties. 
Losses IN Urine.—While the assumption that the urine is 
essentially an aqueous solution of urea leads to grave errors in the 
case of the carnivora, this is still more emphatically true of the urine 
of herbivora, particularly of ruminants. The presence in the urine 
of herbivora of hippuric acid and other nitrogenous compounds less 
highly oxidized than urea has of course long been known, while, 
as stated on p. 27, the presence of considerable amounts of non- 
nitrogenous organic matter was subsequently demonstrated by 
Henneberg and by G. Kihn in the urine of ruminants. 
It follows from these facts that the energy content of the urine 
of these animals must be higher in proportion to its nitrogen than 
is the case with carnivora or with man, but the experimental dem- 
onstration of this fact and the realization of the extent and im- 
portance of the difference are of comparatively recent date. 
Catile.—It is to Kellner * that we owe the first direct. determi- 
nations of the potential energy of the urine of cattle. The two 
animals used in the experiment were fed, the one (A) on meadow 
hay, and the other (B) on meadow hay and oat straw. The results 
as regards the urine were as follows, per day and head: 
* Loc. cit., 47, 275. 
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