DIGESTION EXPERIMENTS WITH SHEEP. 187 
DIGHSTION EXPERIMENTS WITH SHEEP. 
BVeG woes iL bo wND CHAS, Do WOODS, 

—— 9+¢e 
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 assim1- 
lated. 
Partly to add to the stock of knowledge upon this important 
subject and partly because of the need of the results for use in 
connection with its feeding experiments, the Station began 
two years ago a series of digestion experiments with sheep.* 
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 excrement of the animals 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 contained 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. 
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. 

*See Report of this Station of 1894, pp. 107-134. 
