

NITROGENOUS FKEDING STUFES. 85 
woody fiber and other ‘‘ ballast,’’ the more muscular work is 
required for chewing the food and for moving it through the 
alimentary canal. At the same time much more energy is 
required to supply the digestive juices for handling this 
material. In other words, the unequal ‘‘ ease of digestion ’’ 
brings it about that the actual nutritive values of the food 
materials are quite different from those calculated simply 
from their composition. It has been estimated that the nu- 
trients which are assimilated from coarse fodders may yield the 
organism one-fifth less energy for its ordinary work than the 
same amount assimilated from grain, since the coarse fodder 
requires so much more energy fox its digestion. ‘This means 
that a given number of pounds of actually digestible protein, 
fat, and carbohydrates in coarse fodder are really worth con- 
siderably less for feeding than the same amount in a more 
digestible concentrated fodder. 
The following statements by Prof. Zuntz of the Royal Agri- 
cultural High School, Berlin, Germany, who has devoted much 
experimental inquiry to these subjects, are of especial interest :* 
‘‘ It must be said that even when an animal performs no external muscular 
labor, nutrients must still be metabolized for the production of energy. This 
energy is required for the beating of the heart, the muscular movements of 
respiration, and in much greater degree for the processes of digestion. Accu- 
rate measurements have been made of the energy expended in digesting food. 
The increase in the consumption of oxygen when food is chewed has also been 
determined and found to be equal to 51 to 59 per cent. of the amount consumed 
when no work is done, 
"It is well known that it takes a horse much longer to chew 1 kilogram of 
coarse fodder than the same amount of grain. It has been found that the oxy- 
gen consumption increasés 11.4 literst for the labor of chewing 1 kilogramt of 
oats, 7.7 liters for 1 kilogram of corn, and 33.7 liters for 1 kilogram of hay. 
From these figures the quantity of nutrients which must be metabolized to carry 
on the work of chewing can be calculated. For oats it is found to be 2.8 per 
cent. of the total quantity assimilated, for corn 1.4 per cent., and for hay 11.2 
per cent. Closely connected with the labor of chewing and swallowing is that 
expended in the muscular movements of the stomach and intestines and in the 
secretion of digestive juices by the various glands.. The amount of this work, 
as well as the material necessary to maintain it, may in a way be estimated by 
comparing the increased consumption of oxygen during the few hours immedi- 
ately following the consumption of food with that observed during hunger. It 
might be thought that this increase was due to the presence of the nutrients 
taken into the circulation; that is, that the nutritive materials used were increased 

! 
* Experiment Station Record, Vol. VII., pp. 547, 548. 
7 One liter is 1.06 quart, liquid measure. {One kilogram is very nearly 2.2 pounds. 
