108 STORRS AGRICULTURAL EXPERIMENT STATION. 
DIGESTION EXPERIMENTS—HOW CONDUCTED. 
A digestion experiment is usually managed as follows: Selected 
animals are fed with the kind or kinds of feeding stuffs to be 
tested. The feeding stuffs are carefully analyzed. 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 excre- 
ment 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 assimilated 
by the animals. 3 
While such an experiment seems comparatively simple, it is 
surrounded by a number of difficulties which make the work 
laborious and tend to make the results somewhat uncertain. 
INFLUENCE OF THE ANIMAL UPON DIGESTIBILITY. 
The results of digestion experiments in Germany warrant the 
following general conclusions upon the influence of species, breed, 
etc., upon digestibility of feeding stuffs. ° 
Lnfluence of Kind of Animals.—Al\l ruminants, such as cows, 
oxen, sheep and goats, seem to digest practically the same amount 
of protein, fat, nitrogen-free extract and fiber from the same 
kind of food. In general, horses digest less of the food con- 
stituents than do ruminants. ‘This is especially true of the fiber 
and fat in the hays and grasses. | 
Lnfluence of Lreed.—The influence of breed upon digestibility 
has been studied with sheep, but no differences due to breed 
have been found. In general, it is probably true that different 
breeds of animals of the same species digest practically the same 
amounts of nutrients of the same food. 
Influence of the Individual.,—Individual differences have always 
been observed. ‘The variation is quite wide, and on this account 
the results with the influences of kinds and breed of animals are 
somewhat obscured, variations in amounts digested by different 

* For explanation of constituents and uses of feeding stuffs, see pp. 43 and 44 of this Report. 

