Mar. 1, 1925 
Calorimetric Investigations with Cattle 
399 
Table IV .—Computed heat production as affected by loss of carbon during drying 
Cow 
No. 
Period 
No. 
Method I. Carbon 
of air-dry sub¬ 
stance; carbon 
and energy cor¬ 
rected for loss of 
N 
Method II. Carbon 
of the fresh sub¬ 
stance; energy 
corrected for loss 
of N 
Method III. Carbon 
of the fresh sub¬ 
stance; energy cor¬ 
rected for loss of N 
and for C uncom¬ 
bined with N 
Com¬ 
puted 
heat 
produc¬ 
tion 
Com¬ 
puted 
ob¬ 
served 
Com¬ 
puted 
heat 
produc¬ 
tion 
Com¬ 
puted 
h- ob¬ 
served 
Com¬ 
puted 
heat 
produc¬ 
tion 
Com¬ 
puted 
- 5 - ob¬ 
served 
874 
Calories 
11,163.7 
Per cent 
101.8 
Calories 
11,639.2 
9,794. 9 
Per cent 
106.2 
Calories 
11,279.2 
Per cent 
102.9 
ill_ 
9,334.0 
102.8 
107.9 
9,445.2 
10,649. 5 
104.1 
887 
fl- 
10,542.4 
102.1 
10,983.2 
106.4 
103.1 
Ul_ 
8, 663.8 
103.2 
9,142. 6 
108.9 
8,733.4 
104.0 
886 
/I_ 
12,923.8 
95.9 
13,972.1 
102.9 
13,176.0 
12,268.1 
97.0 
ill_ 
12,017.1 
96.7 
13,050.2 
105.1 
98.8 
fl_ 
12,472. 7 
100.8 
13,413.8 
108.5 
12,701.3 
102.7 
887 
II_ 
8,715.6 
101.0 
9,424.6 
109.2 
8,887.9 
103.0 
III_ 
10,270.0 
104.0 
10,928.1 
110.7 
10,429.9 
105.7 
IV_ 
11,871.8 
101.7 
12,442.9 
- 106.6 
12,010.5 
102.9 
Experiment No. 
221f. 
221 f. 
221f_ 
221 g 
In consideration of the loss of carbon 
on drying the feces-and-urine mix¬ 
ture, the results of Method I are 
seemingly paradoxical. Why, one may 
ask, by using a figure for carbon in the 
feces and urine, known to be much 
lower than the correct value, does the 
computed heat production agree closely 
with the observed, in fact, in most 
cases, even more closely than when 
computed by Method III? The answer 
lies in the details of the computation. 
Referring to the general formula for 
heat production, H = F—E —G, it is 
seen that H remains unchanged if G is 
increased and E is decreased simultane¬ 
ously by the same amount. When, in 
computing the balance of carbon, the 
carbon lost through fermentation is 
ignored, the figure for carbon in the 
excreta is low, and the apparent gain 
of carbon and, therefore, of energy (G) 
is correspondingly high or the loss low. 
On the other hand, if one ignores that 
portion of energy of the feces and urine 
which was lost in drying as a result of 
the fermentation, the energy of the 
feces and urine (and therefore E) is 
low. These two factors, therefore, op¬ 
pose each other, the net effect being the 
difference between the two. For ex¬ 
ample, in experiment 22If, 874-1, the 
carbon calculated to have been lost 
from the excreta by fermentation was 
38.3 gm. This being ignored, the 
balance of carbon showed a gain which 
was 38.3 gm. too high. This is equiva¬ 
lent to 50.06 gm. of fat (38.3X1.307), 
or in terms of energy, 475.5 Calories 
(50.06X9.5). G is therefore 475.5 
Calories too high. The heat lost in 
fermentation, computed from the car¬ 
bon, was 360.0 Calories. This being 
ignored, E is too low by 360.0 Calories. 
The net effect on the computed heat 
production is therefore 360.0—475.5 = 
— 115.5 Calories, which accounts for the 
difference between I and III in Table 
IV (11,279.2-11,163.7=115.5). 
To state this somewhat differently, 
since the metabolizable energy equals 
the gross energy of the feed minus the 
energy of the feces, urine, and methane, 
when the metabolizable energy and the 
energy of the body gain are increased 
simultaneously the net effect on the 
computed heat production equals the 
increase of the former minus the in¬ 
crease of the latter. Thus, in the case 
just cited, the metabolizable energy is 
too great by 360 Calories, while the 
energy of the body gain is too great by 
475.5 Calories. The net effect on the 
computed heat production is, there¬ 
fore, 360.0—475.5=—115.5 Calories. 
Thus it is possible to obtain a 
figure for heat production, which may 
agree closely with the observed, as a 
result of a balance of opposing errors. 
The results of Method II show 
unusually large differences between the 
computed and the observed heat 
production, the carbon in the feces 
and urine as determined in the fresh 
substance being used, and the energy 
lost in fermentation ignored. 
The results of Method III are as they 
appear also in Table II. The basis for 
the computation and the possibilities 
of error have already been considered. 
The results as set forth in Tables III 
and IV indicate the need of rigorous 
control of the conditions of drying the 
feces and urine, and further investiga¬ 
tion of the nature of the material lost 
during drying. 
