356 
Journal of Agricultural Research 
Vol. XXI, No. s 
puted in proportion to the two-thirds power of the live weight, gives 
9,788 and 12,184 calories, respectively, as the daily total heat produc¬ 
tion on maintenance by the Jersey and Holstein cows of the assumed 
weights. The heat emission by radiation and conduction, the water 
vapor, and the carbon dioxid produced by cows on maintenance have 
been computed by the methods just described and are included in the 
summary of the results of the computations on dairy cows in Table VIII. 
Table; VIII.— Heat, water 'vapor , and carbon dioxid produced by typical cows per day 
and per head 
Animal. 
Total heat 
emission. 
Heat emis¬ 
sion by 
radiation 
and con¬ 
duction. 
Latent 
heat of 
water 
vapor. 
Water 
vapor. 
Carbon 
dioxid. 
Jersey cow producing 20 pounds 
Calories. 
Calories. 
Calorics. 
Gut. 
Gin. 
of milk. 
16,313 
12,235 
4,078 
6,947 
6, 525 
Jersey cow producing 30 pounds 
of milk. 
18. 273 
705 
4,568 
7,782 
7.309 
Holstein cow producing 30 pounds 
of milk.... 
r 9 > 9 °S 
14, 929 
4,976 
8 ,477 
7.962 
Holstein cow producing 45 pounds 
of milk. 
22,372 
9, 788 
16, 779 
5 . S 93 
9. 528 
8, 949 
Jersey cow on maintenance. 
7 > 34 1 
2,447 
3.046 
4, 169 
3 . 915 
4 , 874 
Holstein cow on maintenance. 
12,184 
! 3 8 
S. 189 
HEAT PRODUCTION OF HORSES 
HEAT INCREMENT DUE TO THE CONSUMPTION OF FEED 
While the general principles of the computation of the fasting katabo- 
lism of horses are essentially the same as for cattle, the computation of 
the heat increment due to the consumption of feed is a much more 
complicated process. The reason for this lies in the fact that no calori¬ 
metric experiments for the direct determination of the heat production 
and of the balance of energy have been made with horses, and conse¬ 
quently an indirect method of computation of the heat increment has to 
be resorted to, which involves many estimates and calculations. 
From the results of their experiments, Zuntz and Hagemann ( 18) 
estimate that the metabolizable energy of the feed of a horse equals 1,796 
calories per pound of digestible nutrients; and they assume, on the basis 
of Magnus Levy's experiments on man, that 9 per cent of the metaboliza¬ 
ble energy of the digestible nutrients consumed by a horse is converted 
into heat in the process of digestion. They furthermore compute from 
the results of their own experiments that each pound of total crude fiber 
consumed increases the heat production by 1,202 calories additional, so 
that the total heat increment due to consumption of feed by the horse 
is the sum of these two amounts. It is obvious that this method of 
computation necessitates a knowledge of the digestibility and of the 
total crude fiber content of the feed. 
