354 
Journal of Agricultural Research 
Vol. XXI, No. 5 
Adding to this the fasting katabolism of the Jersey cow, 5,580 calories, 
gives the total heat production per day as 16,313 calories. 
Computed by this method, the total heat production by the cows per 
day per head is shown in Table IV. 
Table IV .—Total heat production by typical cows per day per head 
Animal. 
Calories. 
Jersey cow producing 20 pounds of milk. 
3 I 3 
18, 273 
19, 9 °S 
22, 372 
Jersey cow producing 30 pounds of milk. 
Holstein cow producing 30 pounds of milk. 
Holstein cow producing 45 pounds of milk. 
HEAT GIVEN OFF BY RADIATION AND CONDUCTION AND AS LATENT HEAT 
OF WATER VAPOR 
The heat emission as computed above includes that given off by radia¬ 
tion and conduction and the latent heat of the water vaporized. The 
latent heat of water vapor, however, can hardly be regarded as available 
for ventilation purposes, inasmuch as under average conditions there is 
no considerable accumulation of condensed water, the water vapor 
being removed from the bam as rapidly as it is produced by the animals 
so that there is little chance for its latent heat to be liberated. 
From the experiments on cattle with the respiration calorimeter it 
has been found that except on very heavy rations the latent heat of water 
vapor constitutes approximately 25 per cent of the total heat given off, 
while about 75 per cent is eliminated by radiation and conduction. On 
this basis, the heat emission by radiation and conduction and as latent 
heat of water vapor per day per head for cows has been computed 
(Table V). 
Table V. —Heat given off by radiation and conduction and as latent heat of water vapor 
per day per head by typical cows 
Animal. 
Heat 
emission 
by 
radiation 
and 
conduction. 
Latent 
heat 
of 
water 
vapor. 
Jersey cow producing 20 pounds of milk. 
Jersey cow producing 30 pounds of milk. 
Calories. 
12, 235 
137 705 
14, 929 
16,779 
Calories. 
4,078 
4, 568 
4,976 
5.593 
Holstein cow producing 30 pounds of milk. 
Holstein cow producing 45 pounds of milk. 
WATER VAPOR PRODUCED BY COWS 
The computation of the amount of water vapor produced by an ani¬ 
mal when the latent heat of the water vapor is known is a very simple 
matter. The latent heat of 1 gm. of water vapor is 0.587 calorie. By 
