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 welt 
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. ae 
Digestion Coefficients for Ruminants 
Dry ata : j i) Nitrogen- 
aiation Protein Fat- Fiber sie 
Pasture grass 71 70 63 7. | %3" 
Green alfalfa. . he 61 74 39 43 72 
Timothy hay 55 48 50 50 62 
Meadow ‘hay 61 57 53 60. 64 
Indian corn. eoidiiece Micaied Oh 68 55 74 65 73 
Corn stover....:........ 57: 36 67 64 59 
Corn silage............. 66 50 82 64 71 
Corn meal............... 88 66 91 — 92 
Oatsescacsi sees tere ee 70 77 89 31 77 
Wheat bran............. 66 77 63 41 71 
Wheat middlings.....:.. 82 88 86 36 88 
Pea meal............... 87 83 55 26 94 
Linseed meal (old process) 79 89 89 57 78 
Cotton-seed meal........ 77 83 94 35 78 
Mangels................ 87 70 —_ 37 95 
Sugar beets............. 92 72 _— 34 97 
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 ard 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- 
*Bulletin 77, Office of Experiment Stations; Massachusetts Report, 
1912; Henry, “ Feeds and Feeding,” p. 574; Jordan, “ The Feeding of Ani- 
mals, p. 427. 
