NUTRITIVE VALUE OF FEEDING STUFFS 41 
The results show that the dry matter of the corn silage was 
found to be 62.9 per cent digestible, the protein 55.3 per cent, the 
fet 82.1 per cent; i.e., the digestion coefficients for the different com- 
ponents in the feed were as follows (leaving off fractions): Dry 
matter, 63; protein, 55; fat, 82; fiber, 45; nitrogen-free extract, 
72, and ash, 18. 
If the digestion coefficients for the organic matter in silage is 
wanted, it is readily obtained by calculating the amount of this 
component in the feed and feces, as follows: In silage, 20.55 (dry 
matter) minus 0.88 pound (ash) equals 19.67 pounds (organic 
matter) ; in feces, 7.62 less 0.72 equals 6.90; 19.67 less 6.90 equals 
12.77; percentage digestible, 12.77 divided “by 19.67 equals 64.4. 
It was found, therefore, that 64 per cent of the organic matter of 
‘the silage was digestible. 
In the case of feeding stuffs that cannot be fed alone (i.¢., a grain 
feed for ruminants) it is necessary to feed it along with some feed 
of known digestibility that will supplement it so that when fed 
together they will make at least a fairly normal ration. The cal- 
culated amounts of digestible components in the second feed are 
then deducted from the total digestible amounts of the various 
components in the ration fed, and the difference is calculated on a 
percentage basis of the total amounts present in the feed whose 
digestibility was to be determined (Fig. 8). 
Interpretation of Results.—The figures obtained in digestion 
trials show the proportion of the components of the feed that have 
been dissolved by the digestive fluids of the body and retained for 
the uses of the animal. This is true only in a general way, for 
various factors render the matter much more complicated. There 
reappears in the dung not only the undigested matter of the feed, 
but small amounts of residues of the digestive juices, waste prod- 
ucts in the activity of the digestive organs, and intestinal mucus. 
A correction can be made, however, for the presence of these in the 
dung by determining the amounts of these waste products. This 
is done by means of artificial digestion of the dung with a pepsin- 
hydrochloric-acid solution (Kiihn’s method), and making proper 
deductions for these in the calculations. Another and more serious 
source of error is introduced by the fact that the feed is subjected 
to the action of bacteria and ferments in the paunch and intestines, 
through which gaseous products are formed, as previously stated 
(p. 30). These attack especially the fiber of plant materials, and 
the figures obtained for the digestibility of these components, there- 
fore, include a portion which has not been dissolved by the digestive 
