Feb. a, 1924 
Digestibility of Tested Grain Hulls 
259 
EFFECT OF SODIUM HYDROXID ON THE DIGESTIBILITY AND FEEDING VALUE 
OF THE HULLS 
This is revealed by a study of the digestion coefficients of the various 
constituents of the hulls. For the purposes of this investigation we 
need consider only the digestion coefficients of the total dry matter, 
crude fiber, nitrogen-free extract, pentosans, and lignin. These are the 
important constituents, the protein, fat, and ash being present for the 
most part in unimportant amounts. Table VII presents the results in 
condensed form. For the benefit of the critical student it is appropriate 
to remark that the digestion trials were conducted with the greatest care. 
Where the coefficients from two individuals differ materially, it should 
be borne in mind that work of this nature can not be controlled in the 
same way that laboratory determinations can be. Biological processes 
are too complex to permit it; and it frequently happens also that the 
individuality of the animal exerts an influence on the final result. Ac¬ 
cordingly the coefficients must be viewed as giving general rather than 
absolutely definite results. 
Careful scrutiny of the individual and average digestion coefficients 
reveals the following facts: 
The digestibility of the total dry matter was substantially increased by 
treatment in case of the oat, barley, and rice hulls. 
The digestibility of the crude fiber, nitrogen-free extract, and pentosans 
in oat, barley, and rice hulls was markedly increased by treatment. 
The results in case of lignin are not so consistent, but it must be 
remembered that treatment has changed its molecular structure, hence 
the data can not be considered of any particular value. It seems evident 
that in the untreated material, in several instances, some little use was 
made of the lignin complex, the results varying with the different mate¬ 
rials. After treatment, in case of the oat, rice, and barley hulls the digesti¬ 
bility of the lignin residue seems to have been somewhat improved. In 
view, however, of our incomplete knowledge of the structure of the lignin 
molecule and of the varying results secured with two sheep on the same 
material, it may be concluded that lignin is of quite doubtful value as a 
source of nutrition. Some investigators consider it to be entirely indiges¬ 
tible. 
In addition to the facts mentioned under Table VII, the following 
general statements seem to be warranted: 
Expressed on a percentage basis, treatment with varying strengths of 
dilute NaOH invariably increased the total digestible dry matter of oat 
hulls, barley hulls and rice hulls. In the majority of cases it also in¬ 
creased markedly the digestibility of the important constituents of these 
materials. 
Cottonseed hulls and flax shives appear to have been unaffected by the 
treatment. It is probable that the lignin-cellulose linkage was broken 
only to a slight extent, due no doubt to the higher degree of lignification 
in these materials, as compared with the hulls of the cereal grains. 
Although the rice hulls showed by far the greatest response to the action 
of the soda, the original material was so much inferior in digestibility to 
the untreated oat and barley hulls that the net result of treatment was a 
product considerably inferior in total digestible nutrients even to the 
untreated oat hulls; hence the action of soda on this material is not likely 
to be of economic value. 
