NUTRITIVE VALUE OF FEEDING STUFFS 



43 



Coefficients of Digestibility. The average digestion coeffi- 

 cients for a number of important feeding stuffs are given in the 

 following table. Complete compilations of digestion coefficients 

 determined for American feeding stuffs will be found in several 

 U. S. Department of Agriculture and State publications, as well 

 as in standard reference books on the subject; these compilations 

 also give the number of separate trials conducted and the number 

 of animals experimented with in each case, as well as the variations 

 in the results of the separate trials. 1 



Digestion Coefficients for Ruminants 



Respiration Studies. The second method by which the nutri- 

 tive effect of feeding stuffs may be studied is by respiration experi- 

 ments, involving the use of either a respiration apparatus or a 

 so-called respiration calorimeter. 



The Respiration Apparatus. The first apparatus of this kind 

 was constructed by Pettenkofer, the great Munich chemist. It 

 consists of a large air-tight chamber, through which a measured 

 current of air is maintained. The animal experimented with is 

 kept in this chamber for a given period, 24 hours or longer. By 

 weighings and analyses of the feed, water, and air taken in by the 

 animal, as well as of the gaseous and solid products given off, 

 the intake and outgo of carbon, nitrogen, oxygen, and other ele- 



1 Bulletin 77, Office of Experiment Stations; Massachusetts Report, 

 1912; Henry, "Feeds and Feeding," p. 574; Jordan, "The Feeding of Ani- 

 mals," p. 427. 



