464 PRINCIPLES OF ANIMAL NUTRITION. 
putation, however, it seems possible to secure an approximate idea 
of the relation of added food to gain. 
By subtracting from the food digested in Periods II-VI the 
average amount digested in Periods I and VII, on the basal 
ration, we find the amounts of added food, consisting chiefly of 
proteids. Reckoning the metabolizable energy of the added pro- 
teids at 4.958 Cals. .per gram (compare p. 317), that of the crude 
fiber and nitrogen-free extract at 3.674 Cals., and that of the ether 
extract at 8.322 Cals., we get the approximate metabolizable energy 
of the added food, and can compare it with the energy of the corre- 
sponding gain. Thus for Period II we have the following: 
DIGESTED. 
Nitrogen- 
Protein,* Crude f Ether 
Grms’ | ie | mixtmet, | “ome 
Period IT ................- 211.33 280.77 643 .22 20.88 
Periods I and VII.......... 101.05 277.91 633 .12 21.60 
Difference............... 110.28 2.86. 10.10 —0.72 
; “12.96 
Equivalent metabolizable' Cals. Cals. Cals. 
(2) 02) of 546.8 BE Bi- Weiss acateye ¥ ax —6 
* Protein of basal ration and of feces equals N X 6.25; that of conglutin 
or flesh-meal equals its total organic matter. 
GAIN, 
Protein Grms. Fat, Grma. 
Period Il .......... 15.00 69.27 
Periods I and VII. .. 6.85 k 19.66 
Difference ........ 8.15 49.61 
: Cals. Cals. 
Equivalent energy 46.3 471.5 
The figures for the gain are those given by the authors, based 
on the assumption of a uniform excretion of methane throughout 
the experiments; the gain of protein includes that contained in the 
wool produced. The animals gained slightly in weight, in addition 
to the growth of wool. Computed on this basis, the percentage of 
the energy of the added food which was utilized was as follows: 
