MILK PRODUCTION AND BODY INCREASE OF DAIRY COWS 
15 
institute of the carbon dioxide given off by the man engaged in milk- 
ing in the calorimeter gave 1.0275 grams carbon dioxide per minute 
for a man weighing 66 kilograms. This amount of C0 2 indicates that 
the milking of a cow by an experienced milker can be classed as 
light work in so far as represented by the output of energy and car- 
bon dioxide. The corrections for the milker which have been used 
are 0.04327 Calorie, 0.01557 gram C0 2 , and 0.02231 gram H 2 per 
minute per kilogram of body weight. These values were obtained 
from the average figures recorded by Atwater and Benedict (4) for 
two men doing work usually for eight hours per day, described as 
"more or less severe," and as "reasonable and not at all excessive" 
by reducing their values to correspond to the carbon dioxide found 
by an actual determination for the man while milking. Twice it was 
necessary during the calorimeter experiments for a man to enter the 
calorimeter chamber for a period of less than a minute. This time 
has been added to the milker's time and the same correction applied. 
The total carbon leaving the animal as carbon dioxide is given in 
Table 10. 
THE NITROGEN AND CARBON BALANCE 
In order to determine the metabolizable energy it is necessary to 
correct the urine for gain or loss of nitrogen in the body, hence the 
need of computing the nitrogen balance. Further, in order to com- 
pute the percentage recovery of the feed matter and energy in the 
milk, the gain or loss of body protein and fat must first be determined. 
This is made possible by having the income and outgo of nitrogen 
and carbon balanced. From the nitrogen and carbon balances the 
corresponding gain or loss of protein, fat, and energy are computed. 
The results of such a balance of nitrogen and carbon are found in 
Table 11. The data for the income and outgo of dry matter and the 
balance of water per day and per head will be found in Tables IV to 
VI of the appendix. 
METABOLIZABLE ENERGY 
According to the writers' definition of metabolism — the total of 
the chemical changes which the constituents of the resorbed feed 
undergo in the course of their utilization and their conversion into 
excretory products — metabolizable matter and energy could, generally 
speaking, represent not only the feed but also such tissues of the body 
as may be katabolized. However, in connection with studies deal- 
ing with the principles underlying animal feeding, it is necessary 
to use the term metabolizable in a more restricted sense. 
Table 10. — Total carbon dioxide ! leaving the animal 
Period 
As measured 
Man milking 
Cor- 
Cow No. 
Total 
COi* 
Carbon as 
C0 3 
C0 2 
Carbon 
Energy 
rected 
carbon 
631 
f I 
\ II 
III 
f 1 
\ II 
I HI 
{ A 
Grams 
5, 169. 81 
5, 529. 05 
5, 828. 38 
5, 165. 51 
5, 353. 07 
5, 469. 35 
5, 951. 13 
5, 857. 07 
Grams 
1,409.80 
1, 507. 77 
1, 589. 40 
1, 408. 63 
1,459.78 
1,491.49 
1, 622. 87 
1, 597. 22 
Grams 
13.8 
11. 1 
Grams 
3.87 
3.11 
Calories 
39.50 
31.70 
Grams 
1, 405. 93 
1, 504. 66 
1, 589. 40 
615_ 
579 
18.9 
20.5 
21.9 
19.3 
22.7 
5.29 
5.74 
6.14 
5.41 
6.36 
53.97 
58. 54 
62. 55 
55.12 
64.82 
1, 403. 34 
1,454.04 
1,485.35 
1,617.46 
1,590.86 
1 Corrected for carbon dioxide outgo of man entering the colorimeter to milk the cow 
'Factor C in COj, 0.2727. 
