156 STORRS AGRICULTURAL EXPERIMENT STATION. 
THE DIGESTIBILITY OF FEEDING:s7 UEES: 
BY CHAS. D;-WOODs; 
It is a matter of every-day experience that only a part of the 
food eaten is actually used by the animal. It is, therefore, of 
importance in cattle feeding to have a knowledge, not only of the 
chemical composition of a given food, but of the amounts of the 
nutrients, which are capable of being assimilated. It is not so 
much what an animal eats, as that which it digests, that is actually 
turned to account. 
The word digestibility as commonly used has more than one 
meaning. People often speak of one food as being more digest- 
ible than another, when they mean it is more quickly or easily 
digested. As here used, the term digestibility means the pro- 
portion of any given food or food constituent which is digested 
under usual conditions, without regard to the time needed or the 
ease of digestion. 
DIGESTION EXPERIMENTS—HOW CONDUCTED. 
A digestion experiment is managed as follows: Selected ani- 
mals are fed with the kind of food to be tested, the chemical 
composition of which has been ascertained by careful analysis. 
A weighed portion is fed, care being taken to see that none is 
wasted, and that all the uneaten residues are weighed and 
analyzed. In this way the exact weights of protein, fat, fiber, 
nitrogen-free extract and ash eaten are ascertained. The solid — 
excrement of the animal contains the undigested residues. This 
is carefully collected, dried, weighed, and analyzed, and the © 
amounts of undigested protein, fat, fiber, nitrogen-free extract 
and ash contained in it are found. The difference between the 
amounts found in the undigested residues and the amounts con- 
tained in the food eaten is taken as a measure of the amounts 
of the various nutrients which have been digested and assimi- 
lated by the animals. 
While this experiment seems comparatively simple, it is sur- 
rounded by difficulties which render the work laborious and tend 
to make the results somewhat uncertain. 

