It is satisfying to realize that most poultry houses are more comfortable for the birds, and their caretakers, than outside conditions during hot weather.
The primary reason poultry are kept in buildings is to provide them with a comfortable, safe environment with protection from challenging weather, such as overly hot or rainy conditions. Ventilation, more appropriately thought of as an environmental control system, is key to assuring good indoor conditions. Providing good ventilation is a very important aspect of management for small-scale flock owners and commercial scale production.
To appreciate how to keep birds comfortable during hot summer conditions, we must realize that birds are much more sensitive to high humidity than us humans. Although both poultry and people favor a comfortable thermoneutral temperature around 70 degrees, birds need to release excess body heat via evaporation, which is compromised in high humidity conditions. About half of poultry body heat is lost through evaporation via respiration that shows as panting when birds get too warm. For comparison, people only lose about a quarter (28%) of their body heat via sweat evaporation and respiration when we are too warm.
For poultry, panting results in decreased feed consumption, leading to loss in egg production in layers and weight gain in meat birds. Decreasing air temperature of the barn and moving more air across birds are solutions to poultry heat stress.
Natural or Mechanical?
Ventilation replaces stale, warm, humid air in the poultry building with fresh air from outside. There are two primary types of ventilation systems used in poultry houses — mechanical and natural.
Nearly all commercial scale poultry houses use mechanical ventilation today. Mechanical ventilation systems use fans to ensure consistent and predictable airflow.
Natural ventilation takes advantage of naturally occurring forces, primarily wind, to move air in and out of the building.
In either type of ventilation, a pressure difference is the driving force that causes air to flow into and out of the poultry house. In mechanical ventilation systems, we manage a static pressure difference between the poultry building interior and the outside to ensure proper air exchange and distribution.
As we move into warmer summer conditions, we want to keep the poultry building within a comfortable temperature range for bird welfare. Poultry buildings can be warmer than outdoor conditions, primarily due to the birds’ body heat.
We can keep this rise to a minimum and make the building cooler and more comfortable than outdoors. For starters, the building does shade birds to reduce overheating from direct solar exposure. As building air increases above the desired temperature of around 70-75 degrees, the ventilation air exchange is increased to bring in more fresh, cooler air by running more exhaust fans or opening large natural ventilation openings. The key is to assure fresh air speed over the birds to assist cooling via evaporation from their respiratory system, and body heat loss via convection. This air speed needs to increase with bird age, with even a small increase in speed making a significant improvement in bird comfort.
During hot weather, once the maximum ventilation capacity is reached, the building temperature begins to rise approximately linearly with further increase in outside air temperature. Therefore, at some point before the temperature is considered stressful for the birds, cooling mechanisms such as evaporative cooling and wind-tunnel type of mechanical ventilation would be activated. These extra cooling systems help maintain the desired temperature and will reduce the temperature to cooler than what the birds would experience in outdoor conditions. In fact, maintaining a breezy air speed at night for large birds will remove more body heat that accumulated over a hot day.
Achieving good ventilation is essential to providing a good indoor environment for poultry. Air exchange by natural or mechanical means can accomplish this goal. Comfortable, cooler indoor conditions can be achieved in modern poultry houses even during hot weather by providing good air speed around birds to aid their ability to cool themselves via respiratory evaporation.
