96 THE STOCKFEEDER'S COMPANION 



digested. It is then easy to calculate by difference 

 the amount and proportion of albuminoids, oil, carbo- 

 hydrates, and fibre digested respectively by the various 

 classes of farm live stock. 



The method adopted for this purpose is briefly 

 as follows : For convenience, a male animal is taken 

 and fed on the experimental food for a week, to get 

 the animal accustomed to the new diet as well as 

 the old diet removed from the system. An indiarubber 

 bag is then placed behind the animal so as to catch the 

 solid excrement. The food is carefully weighed and 

 analysed before feeding, and the dung weighed and 

 analysed by the same method as that employed for 

 the food ; then by subtraction the percentage of each 

 nutrient digested in the food can be ascertained. 



For very accurate determinations of digestibility 

 a further precaution is necessary, more especially with 

 ruminants. Since the food generally ferments in the 

 paunch, gases (carbon dioxide, marsh gas, hydrogen) 

 are generated and disappear in the breath. In a 

 similar manner, food which ferments in the bowels 

 of farm animals in general often decomposes with 

 the evolution of gases which escape from the bowels ; 

 consequently in both cases this part of the food is not 

 digested, and is therefore lost to the animal. It is only 

 since the introduction of a respiration chamber 1 that the 

 amount of loss in this way could be ascertained. 



1 The respiration chamber is an air-tight compartment which 

 is used at a few research stations in Germany, where the animal 

 is placed for short intervals during fattening, etc. The animal is 

 supplied with air of known volume and composition, and from 

 time to time it is drawn off and analysed. In this way the gases 

 which leave the animal are discovered and their amount 

 ascertained. A respiration chamber has now been installed in 

 this country at Cambridge, but no results are as yet available. 



