INVESTIGATIONS ON THE METABOLISM OF MILCH COWS. 1 



Oscar IIagemaxx, Ph. D., 

 Professor at the Agricultural Academy, PoppeUdorf, Germany. 



METABOLISM EXPERIMENTS WITH RUMINANTS. 



When metabolism investigations are carried on with Herbivora — 

 milch cows, for instance — other points must be considered which ren- 

 der the calculations still more complicated. The feeding stuffs are not 

 as simple as in the case of Carnivora. They contain more amid com- 

 pounds than flesh. The ether extract does not consist of fat alone, but 

 of chlorophyll, wax, and similar bodies. Plant protein is not uniform 

 in composition. While animal protein contains on an average 1G to 

 16.7 per cent nitrogen, there is a somewhat wider range in the case of 

 vegetable protein. In addition to starch, the carbohydrates consist 

 of pentoses, pentosans, gums, etc. Finally, vegetable feeding stuffs 

 contain crude fiber, which is only in part digestible, and which is per- 

 haps of paramount importance in investigations of this kind. 



Nitrogen which is digested and is not excreted in the urine is 

 assumed to be stored in the body, and this gain is best calculated as 

 proteid, since, with the exception of a small part which remains in 

 the growing tissue, the nitrogen is transformed into proteid. On the 

 supposition that 4 per cent of the nitrogen in the lymph is nonalbumi- 

 noid nitrogen, and that the quantity of lymph is doubled by very 

 abundant feeding, it is possible for the body to gain a considerable 

 amount of amids without any change in the composition of the lymph. 

 Similar reasoning might be applied to the muscles; but the ratio of the 

 different nitrogenous bodies to each other in the muscles is not known 

 with certainty, nor the proportion in which this nonalbuminoid nitro- 

 gen is eliminated. If, on the other hand, the tissues of the body lose 

 water under intensive feeding, the body may possibly lose nitrogenous 

 extractives, which appear in the urine and so introduce an error in cal- 

 culating the gain of protein. However, such considerations are theo- 

 retical and have little practical value. 



In determining the material digested, slight errors are introduced 

 from the fact that the ether extract of the feces contains numerous 

 bodies which were not originally present in the food, and the nitrog- 

 enous bodies iu the feces have a different composition from those in 



Continued from p. 816. 



903 



