20 
BULLETIN 1281, U. S. DEPARTMENT OF AGRICULTURE 
Since the energy of the digestible nutrients is determined by sub- 
tracting from the gross energy of the feed the energy of the unused 
residue from the same, then all factors whatsoever of unused residuum 
should be consistently accounted for in this computation and that of 
metabolizable energy as well; and, in view of the fact that this is a 
departure from the customar}' usage, the usual method — based upon 
feed constituents minus feces constituents — as well as the improved 
method — considering also other excreta — has been used. That the 
heat of fermentation does not belong either to the digestible or to 
the metabolizable portion seems clear, the only question being as to 
the accuracy of the basis for its estimation. 
The metabolizable energy computed as per cent of the digestible 
(method 1, compare with the usual, and method 2 with the improved 
conception of digestibility) are reported in Table 15. This table 
shows a close agreement from period to period, and also among the 
different animals. 
HEAT EMISSION 
The heat given off by the animal while in the respiration calo- 
rimeter is removed from the apparatus in a current of water, in 
water vapor, in excreta, and in milk, and the sum of the heat thus 
removed corrected for the introduction of feed and water as well as 
for the man engaged in milking, is the total heat emission. Under 
the heading "radiation," etc., in Table 16 is included all the heat 
except that removed as latent heat of water vapor, and in the last 
column the heat by radiation is expressed in per cent of the total. 
This heat emission, however, is not necessarily identical with the 
total heat production of the ration fed, but must be corrected for 
change in live weight of the animal and for any change in the body 
temperature. This correction has the effect of rendering the data 
representative of the body in such condition as at the beginning of 
the experiment. 
Table 16. — Heat emission per day and animal 
Covr Xo. 
Period 
Radiation 
and con- 
duction 
Latent 
heat of 
water 
vapor 
By radi- 
Total ation, etc., 
heat in per cent 
of total 
631 .- 
615 .- 
579 — 
1 " 
I HI 
( 1 
11 
III 
f I 
I II 
Calorics 
7. 359. 6 
f ~ - 
7. 843. 3 
8. 619. 2 
8,871.8 
9, 386. 5 
Calories 
4. 4S7. 6 
4. 4M.fi 
4, 164. 7 
3, v70. 8 
3. 577. 9 
3, 519. 2 
4, 204. 5 
3, S61. 7 
Calorics 
11,847.2 
12, 201. 8 
13, 430. 1 
11,714.1 
12, 197. 1 
12,391.0 
13, 655. 3 
13, 248. 2 
Pit cent 
62.12 
63.52 
68. 9& 
66.96 
70.66 
71.60 
69.21 
70.85 
INFLUENCE OF BODY TEMPERATURE 
The temperature of the body of the animals was taken daily at the 
rectum, by means of the usual clinical thermometer. During the 
feeding in the barn this temperature was always taken at the same 
hour, but during the calorimeter experiment could not be taken at 
the same hour of the day as at the end without destroying the equi- 
librium of the apparatus. Also at this time it had not been learned 
that the thermometer must be inserted to a depth of at least 6 
inches in order to obtain correct readings, as Kriss (6) has subse- 
