Optimizing bird comfort in cool weather (Poultry Production)
(Editor’s note: Georgie Cartanza is an Extension poultry agent with the University of Delaware.)
As the seasons change, swings in temperature from day to night can be quite significant.
Understanding how air is moving and mixing in the poultry house will benefit bird comfort and optimize house conditions.
The goal of the ventilation system in the poultry house is to remove moisture, ammonia, carbon dioxide, and excess heat. The use of fans, vents, tunnel inlets, and attic inlets make this system function to accomplish those goals.
There is a tremendous amount of moisture being deposited in the house. I like to think of the chicken house as a “moisture bank account,” the chickens, the drinking system, and the heating system are making deposits of moisture.
The fans are making withdraws from that bank account.
The starting point for accessing the ventilation of a poultry house should be house tightness. We determine house tightness based off static pressure measured in inches of water column.
The static pressure is measuring the vacuum created by the fans.
To test for house tightness, a good rule of thumb is to select fans that will provide 1 cubic feet per minute of air per square foot of floor space in the poultry house. For example, in a house that is 20,000 square feet., the fan capacity needed would be approximately 20,000 cubic feet per minute.
The fans needed to create the correct amount of cfms should be selected with the goal to create a balance of air movement in the house.
In a center brooded house the selection of a fan on each end of the house would create a balance of air movement.
One fan pulling air more in one direction would cause more cool air to be drawn into one end of the brood chamber.
The second rule of thumb is for every 0.01 point of static pressure pulled; the air can be thrown two feet. If the house is 40 feet wide, we cut the house in half because are pulling air from both sides of the house.
This gives us 20 feet that air must be thrown from the vent boxes across the house to be able mix air properly. In this example, the minimum static pressure would need to be 0.10 (20 feet to move air / 2feet per 0.01 of pressure) with vents open. Good air mixing when the goal is to temper the air is a complement of good static pressure and opening.
Good pressure with too little opening and air comes in fast but loses its “umph” to be thrown to the center because we do not have enough volume of air.
The air ends up coming in and falling before it reaches the first drinker line.
During cold weather, a band of cake may develop because of this between the sidewall and first set of drinkers.
In my experience, it typically takes at least 0.03 points of static pressure above the target pressure to get an inch of opening.
The tighter the house the better, before vents ever open, as this gives the grower more control over where air is entering the house.
Air will take the path of least resistance.
Therefore, any gap around end doors, side doors, tunnel inlet (curtains or tunnel doors), fan louvers, holes in the ceiling, holes in the foundation, seepage at the sill plate will reduce house tightness.
If there is a hole in the foundation, air will more easily be drawn into the house that is not properly mixed leading to moisture being deposited and a draft being created at bird level.
Sealing any gaps will improve house tightness.
The colder the air is the heavier the air will be.
With that being said, in extreme cold weather, a higher target pressure may be desirable because more “umph” will be needed to properly mix air.
The more mild or warm the air is, or the closer the outside temperature is to the target temperature the less critical it is to try to temper the air prior to it reaching bird level.
There has often been some confusion on controllers as to how to utilize the second static pressure.
The theory behind second static pressure is to give the controller a second set of goals to shoot for when the house starts to warm up and the house needs to remove more air because the temperature is getting warmer.
Different controllers go to the second static pressure goals in different ways.
Some will shoot for second static when the temperature gets to a certain point while others may go when a certain fan comes on. Some use inside temperature, while other use an outside temperature sensor.
This feature can be very helpful in the fall and spring when there are big changes in temperature especially from day to night.
The house will utilize first static pressure when the house is minimum ventilating and the air needs to be tempered before it reaches bird level.
As the house warms up and more fans are needed for temperature control, the second static pressure can let more air in the house by opening the vents more.
Allowing the vents to open more at a lower pressure, allows the fans to work more efficiently and draw more air in.
For example, two fans running for minimum ventilation with a target of 0.10 static pressure, the house warms up, three additional fans come for temperature, the house could transition to second static pressure with a goal of a 0.07, this would allow the fans that are running to pull more cfm’s and may prevent another fan from coming on.
The programming of second static pressure should be discussed with your company representative.
Another fundamental concept to understand ventilation is humidity. Managing humidity in the poultry house is critical to animal welfare and good animal husbandry.
The best time to check humidity is first think in the morning.
This is when we have the opportunity to see what the air quality and humidity is throughout the night. Nighttime is when the poorest air quality will occur because this is when we will have the least amount of ventilation; the outside air is cooler and typically contains more moisture.
A good rule of thumb is for every 20 degrees we raise the air temperature the ability of that air to hold moisture is doubled. This is why it is so important we do a good job with mixing and tempering air especially when the temperatures get cooler.
Monitoring humidity is one of your best tools for staying ahead on ventilation. The goal should be around 60 percent, it is going to very throughout a day.
If it is getting to 70 percent while minimum ventilating then most likely, the house is not being ventilated enough.
Circulation fans can be a big help managing humidity and improving litter conditions. During minimum ventilation, fans may run 60 seconds on, 240 off.
There are 240 seconds where there is little to no air movement. Circulation fans keep air moving and help break up the stratification of air and heat.
If clothes where put in a dryer with heat added but they never circulated, it take forever for them to dry.
This concept is true for the poultry house.
Circulation fans can be a relatively inexpensive way improve air, litter quality, and optimize usage of heat.
Ventilation influences so many aspects of a flock’s performance. Being proactive to limit stress is key to succeeding at antibiotic free poultry production.
Managing air quality — keeping humidity under control, limiting temperature swings, and keeping birds at their optimum comfort level will result in better livability, better weight gains, and better animal welfare.
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