Tunnel ventilated poultry houses rely on high wind speeds generated by tunnel fans to produce a “wind-chill affect” and make birds more comfortable during hot weather.
Moving air removes sensible heat from the birds without any energy expended by the birds themselves. Keeping bird’s body temperatures within normal ranges, even during periods of extremely hot weather, keeps the birds eating and growing and makes a flock more productive.
If birds are not kept at a comfortable or “thermo-neutral” temperature, then they will pant to remove excess heat. Karen Christensen, OK Farms, Inc., Fort Smith, Ark., spoke on the effects of tunnel ventilation on large broilers at the USPOULTRY Production & Health Seminar. She said that many times large birds can be seen panting at house temperatures that we tend to think of as normal or thermo-neutral. If a bird is panting, then it is hot and it trying to shed heat. Panting requires energy expenditure by the bird and it is a sign that the bird is not comfortable. Broilers give off a lot of heat; Christensen said that a house full of big birds is like having 24 radiant brooders burning. Each pound of bird gives off 5 BTUs per hour.
Christensen said that the cooling affect of high wind speed achieved in a tunnel ventilated house can lower feed conversion, increase rate of gain and decrease mortality. Companies raising large birds are finding benefits from using wind speeds up to 550 feet per minute. Many older tunnel ventilated houses were engineered for wind speeds of between 400 feet per minute and 500 feet per minute.
Companies have rapidly increased the target live weights for deboning birds. Many complexes that used to raise 6.5 pound birds now raise birds over 8 pounds. Bigger birds require innovative methods to manage bird temperatures in hot weather, according to Christensen. The most successful big bird operations are doing three things. They are using high winds speeds, at least 550 feet per minute in full tunnel mode. Successful big bird operations are also keeping houses in tunnel mode through the day and night. Research has shown that it takes several hours after the outside air cools off at night for the core body temperature of the birds in the houses to cool off. Staying in tunnel mode helps the bird cool off quicker and this keeps them eating and growing better in hot weather. Finally, Christensen said that the most successful big bird operations are using tunnel ventilation on birds at younger ages than in the past.
Tunnel ventilation can provide a more comfortable environment for broilers in hot weather. Bird performance is improved at higher wind speeds than have been commonly used in the past. Additional fans and cooling pad area may need to be added to some older houses so that they can compete with new house designs, particularly for large birds.