312 DAIRY CATTLE AND MILK PRODUCTION 



from the standpoint of the health of the animals, but it is 

 necessary for the most economical production of milk. 

 Dairymen are largely indebted to Professor King for infor- 

 mation on this subject, as well as for the best practical system 

 of applying this knowledge. 



The cow gives off carbon dioxide, moisture, ammonia, 

 marsh gas, and some other organic matter from the lungs. 

 A candle will be extinguished if placed in a jar containing 

 the air exhaled from the cow's lungs. A cow weighing 1000 

 pounds inhales 224 pounds of air in 24 hours, or about double 

 the amount by weight of her food and drink. This is at the 

 rate of 3542 cubic feet per hour. To supply this amount of 

 air for 20 cows will require a ventilating flue 2 by 2 feet, in 

 which the air moves at a velocity of 295 feet per minute. 

 In providing pure air for stables the cubic space per animal 

 has little significance. The important question is the amount 

 of fresh air provided. 



Forces producing Ventilation. There are three main 

 forces that cause movement of air in a stable. 



1. The wind pressure against the side of the building, 

 which tends to force air into the building and out on the 

 opposite side or upward through the ventilators. 



2. The wind in blowing across the top of a ventilating 

 flue produces an outward suction. 



3. The difference in temperature between the air in the 

 barn and that on the outside. This causes an upward move- 

 ment in a ventilating shaft by a force equal to the difference 

 in weight of the air outside and within. 



The King System. This is the system in general use in 

 modern dairy barns. The main features consist of a large 

 flue opening near the floor and extending above the roof of 



