50 
N. C. AGRICULTURAL EXPERIMENT STATION. 
17. THE NITROGEN-FREE EXTRACT OF FOODS.* 
The term “nitrogen-free extract” as used in the ordinary fodder 
analysis represents sugars, starch, gums, mucilages, organic acids, 
etc., or the difference between 100 and the sum of protein, fiber, fats, and 
ash. In coarse fodders, very often, the nitrogen-free extract is half, 
or more, of the total constituents of the food, and is of too varied 
composition and nature to be thrown in so loosely. A step of prog¬ 
ress has recently been made in the separation of the constituents of 
the nitrogen-free extract by the introduction of a method for the 
determination of the pentaglucoses. These varied bodies ot the 
nitrogen-free extract are claimed to have, and perhaps do have, dif¬ 
ferent coefficients of digestibility and nutritive value, but the data 
upon which to base an opinion of either is rather meager. 
In the present experiments total sugars and starch have been 
determined, and all the nitrogen-free extract not represented in them 
is included under the head of “Undetermined Carbohydrates.” 
Under the heading of “Total Sugars” is represented all the cold 
water extract substances capable of reducing Fehling’s copper solu¬ 
tion, and is really more than the true sugars, while under the head¬ 
ing of “Starch” is included all copper-reducing bodies obtained by 
treating the residue from the “total sugars” with 150 oc water and 4 C0 
hydrochloric acid in an Erlenmeyer flask, with a reflux condenser, on 
water-bath for 12 hours. This, too, of course, is not all starch, for 
other bodies than starch have no doubt been converted into sugars, 
but duplicate determinations gave fairly concordant results, showing 
pretty constant conversion power of the acid. 
Though “ total sugars” and “starch”do not here represent definite 
classes of bodies, they are of interest as a means of comparison with 
similar results. The New York State Experiment Station has made 
determinations of the digestibility of sugars and starch in some hays 
and rations, and concludes that “the total of sugars and starch 
digested in each ration falls a little short of the total amount of 
nitrogen-free extract digested.”f The method used by this Station 
and the New York Station for sugars and starch was practically the 
same. 
As will be seen from the table following, the sugars were in all 
cases completely digested. The coefficients of digestibility of the 
“undetermined carbohydrates” of corn fodder, soja bean silage, 
rations of raw and roasted cotton-seed and corn silage, raw and 
roasted cotton-seed, and cotton-seed hulls are much lower than the 
corresponding ones for starch for the same fodders and rations, but 
with the remaining fodders and rations there was very little differ¬ 
ence in the digestibility of starch and “undetermined carbohy¬ 
drates.” (See Table XXXVI.) 
* Mr. J. S. Meng made the determinations of sugars and starch, and to him is 
due credit for the analytical work on this subject as presented in this Bulletin. 
f Eighth Annual Report New York (Geneva) Experiment Station. 
