26 
BULLETIN 1281, U. S. DEPARTMENT OF AGRICULTURE 
METABOLIZABLE ENERGY AVAILABLE FOR PRODUCTION 
If the met aboliz able energy of the feed required for maintenance 
is subtracted from the total metabolizable energy in the feed, the 
amount available for production is obtained. These values as well 
as those of the actual milk production and the body gain in calories 
are recorded in Table 23. 
Having the above data the computation of the percentage utiliza- 
tion and the net energy of the feed for the different types of produc- 
tion can be made. 
Table 23. — Metabolizable energy available for milk production and body gain 
Cow No. 
Period 
Available for pro- 
duction 
Actual production 
Usual 
method 
Improved 
method 
Milk 
Body gain 
631 
f I 
II 
III 
I 
II 
III 
/ I 
\ II 
Calories 
8, 740. 
8, 155. 6 
7, 755. 7 
8, 953. 7 
9, 012. 6 
8, 933. 7 
11, 097. 6 
11, 063. 5 
Calories 
6, 999. 2 
6, 572. 8 
6, 337. 6 
7, 402. 8 
7, 455. 8 
7, 357. 
9, 146, 7 
9, 060. 2 
Calories 
5, 378. 2 
784.1 
Calories 
+221. 4 
+3, 663. 2 
+3, 863. 5 
615_ 
6, 020. 
6, 278. 7 
6, 157. 
7, 023. 6 
6, 749. 5 
+502. 
-160.7 
579 
-650.3 
+384. 7 
+686. 7 
NET ENERGY FOR BODY INCREASE 
In period III cow 631 was dry, and gained body substance equiva- 
lent to 3,863.5 Calories. If this amount of gain is divided by the 
amount of available metabolizable energy, according to the two 
methods of computing it, the following results are obtained : 
3,863.5X100 
7,755.7 
3,863.5X100 
6,337.6 
=49.815 per cent utilization (usual method). 
= 60.961 per cent utilization (improved method). 
Since the body gain expressed in calories (assuming that there 
is no milk production) represents the net energy of the difference 
between the total feed eaten and the amount needed for maintenance, 
the net energy for body production per kilogram dry matter of feed 
mixture is obtained by dividing the calories of body gain by the 
difference between gross intake of feed and the maintenance require- 
ment. 
Thus: 7,151.0-3,963.6 = 3,187.4 grams of feed mixture; and 3,863.5 Calories 
(body gain) -s- 3. 1874 kilograms (gross intake minus the maintenance requirement) 
= 1.2121 Therms net energy per kilogram dry matter of feed for body increase. 
NET ENERGY FOR MILK PRODUCTION 
Turning now to period I, the milk production of cow 631 was 
equivalent to 5,378.2 Calories, and at the same time the body gain 
was equivalent to 221.4 Calories. 
The utilization of the metabolizable energy available for production 
was 49.815 per cent according to the usual method, or 60.961 per cent 
according to the improved method of computation. Using these 
percentages a correction for the 221.4 Calories £ain by the body is 
obtained. Therefore, 221.4 + 0.4982=444.4 Calories, and 221.4* 
0.6096 =363.2 Calories, respectively. Deducting these values from 
