18 
BULLETIN 1231, U. S. DEPARTMENT OF AGRICULTURE 
tation. The gain or loss of body protein and fat, computed from 
the nitrogen and carbon balances, and their equivalents in energv 
are given in Table 13. 
Table 13. — Daily gain (+) 
or loss 
( — ) of body protein, fat, 
and energy 
Cow No. 
Period 
Protein i Fat 
Energy 
Protein 
Fat j Sum 
631.. 
1 I? 
11 
I in 
{ A 
Grams ; Grams 
-24.0 i +37.7 
-36. +407. 2 
—115.8 ' +337.2 
+20.4 i +40.6 
—7.2 —12 6 
Calories 
-136.8 
-205.2 
+660.1 
+116.3 
—4i n 
Calories Calories 
+358. 2 ! +221. 4 
+3,868.4 i +3,663.2 
+3.203.4 +3,863.5 
+385. 7 —502. 
_iiq 7 ; — Ifif) 7 
615 
579 
-42.6 -42.9 -242.8 ' -407.5 -650.3 
—57.0 +6.3 1 +334,9 j +59.8 +384.7 
+10. 8 ^-65. 8 
+61. 6 
+b^o. 1 : +686. . 
The factors used in the computation of the nitrogen and carbon 
balances, as found in Table 11, to the corresponding amounts of 
protein, fat, and energy, recorded in Table 12, are the following: 
Grams of nitrogen multiplied by 6 equals body protein. The average 
per cent of carbon accepted for protein is 52.54 per cent: hence the 
number of grams of protein was multiplied by 0.5254 to get the 
number of grams of carbon in the protein. To compute carbon to 
fat the number of grams of carbon was multiplied by the factor 1.31, 
which corresponds practically to an average of 76.5 per cent of carbon 
in animal fat. The energy equivalents for protein and fat were con- 
sidered to be 5.7 and 9.5 Calories per gram, respectively. 
COMPUTATION OF METABOLIZABLE ENERGY 
The milk of the cow may be considered in the same light as body 
gain, in which case the energy of the excreta must be corrected for the 
potential energy of the milk protein. On the other hand it may be 
considered as a product in a sense apart from the body which, being 
neither body gain nor an excretum, is not involved in the computation 
of metabolizable energy. Although a column setting forth the 
metabolizable energy according to the first view, that is, considering 
the milk as body gain, is given, considering it as a product entirely 
apart from body gain is assumed to be the correct view for this class 
of experiments. 
In Table 14 are found the results obtained by using the following 
three methods of computation: 
No. 1. Gross energy of the feed minus the chemical energy of feces, 
urine, brushings, and methane, the nitrogenous outgo being corrected 
to body nitrogen equilibrium, ignoring the milk. 
No. 2. The same as No. 1 except that the heat of fermentation is 
treated as an excretum. 
No. 3. The same as No. 2 except that the milk is treated as body 
gain. 
In Table 14 the values for the gross energy of the feed and of the 
feces are obtained from the digestibility tables in the appendix. 
The other values needed in the computation are recorded in preced- 
ing tables. A comparison of the metabolizable energy as deter- 
mined by the three methods of computation shows the amount 
metabolizable according to method 2 to be from 17. 2S to 19.92 per 
