Prepare Broiler Houses for Summer Weather

The combination of summer temperatures and humidity in Mississippi can be dangerous for poultry flocks in the state. Poultry growers should plan ahead for the long, hot Mississippi summers.

There are several steps growers can take to prepare for the hot weather. Most of these steps work better (for both you and your birds) if done before July or August. Some may require a small expense (such as new fan belts), but most only require an investment of time. Certain steps are time-consuming or require the fans not to be running. Therefore, these steps must be done before hot weather arrives and while birds are still small, or in between flocks. Plan and do preventive maintenance projects EARLY. There will be plenty of other issues that require your immediate attention daily once hot weather arrives.

Air Speed Is Critical

The growing U.S. demand for large broilers (8½- to 9½-pound range) often makes minimizing heat stress on these larger birds the top priority for broiler producers during summer grow outs. Broiler chickens today do not perform well in heat-stress situations. The primary way to cool broilers is ensuring sufficient air movement to pull heat from the bird. Modern, tunnel-ventilated broiler houses will provide adequate house conditions if they are well maintained and properly managed. However, the 400 ft/min air speed down the house that was acceptable a few years ago is no longer sufficient. Many modern tunnel houses are capable of a minimum of 600–700 ft/min (some may manage 800–1,000 ft/min), and it’s all needed with today’s larger broilers.

A large number of fans allow 600–700 ft/min (or greater) air speed. They are the first line of defense against higher summer temperatures. However, to generate an air velocity of 600 ft/min, the number of tunnel fans required depends on their air-moving capacity at a static pressure of 0.10 inches. Determining the number of fans based on a lower static pressure will reduce the available air speed. In addition, any fan is only as good as its drive belt and pulleys. Belts should be tight and ride high in the pulley for proper performance. Loose belts and worn pulleys cannot spin the blades at the appropriate revolutions per minute creating more wear and hurt fan performance. In most situations, fan belts should be replaced once per year; replace them more often if they ride low in the pulley (Figure 1). Idler/tensioner pulleys that are worn out can also add extra drag or slippage causing belts to prematurely wear out. It is a good idea to inspect the fans between flocks.

Fan blades, shutters, and guards also must be kept clean. Numerous field studies indicate that dirty shutters can reduce airflow by as much as 30 percent. Also, don’t forget the bearings. A dry bearing requires more power to turn. This results in a loss of fan efficiency and shortens the life of the bearing. Lubricate bearings twice per year (spring and fall) if they have a grease fitting and are not sealed. Some bearings are sealed and do not require lubrication. However, you should remove the protective guard or shutter and use a grease gun to manually grease any bearings and grease fittings (Figure 2) twice per year. It is also a good idea to keep some spare parts on hand in the event something goes out. Having an extra motor, belts and pulleys can get you back going quicker than making a special trip to the supply house.

Especially when growing larger birds, having enough air speed is critical. But just as important is having a uniform air speed from side-to-side and end-to-end of the house. Only about 1/3 or more of your birds will receive adequate cooling if you have 700 ft/min air speed down the center of the house but only 300–400 ft/min near the side wall. It is better to have 600 ft/min throughout the house than to have 750 ft/min in the center and 350 ft/min near the sidewalls.

Smooth, solid sidewalls work better than curtain-sided houses or solid wall houses with exposed posts. Smooth, solid sidewall houses usually have less than 20 percent variation in air velocity between the sidewalls and the center of the house, while most curtain-sided houses have variations in air velocities ranging from 30 to 50 percent. This is because exposed posts create an uneven surface that tends to force air off the sidewall and greatly reduce air velocity along the walls. Wall-mounted space furnaces will have the same effect. Anything other than a smooth wall surface will create turbulence, significantly reducing air speed over birds near the sidewalls.

Check the Cool Cell System

Uniform air speed is critical, but during extremely hot weather, you need a second line of defense: the cool cell system. To provide the most benefit, you must maximize the amount of wetted pad surface the air passes through. A dry pad area allows hot air to pass directly into the house and reduces the cooling effect of the wetted pad area.

Preventive maintenance on the pad system is just as important as fan maintenance. Clogged pads force the fans to work harder, reduce the wind-chill effect, and reduce cooling. The flutes should be free of dust, cobwebs, and especially mineral deposits. Mineral buildup over time can eventually ruin a set of pads, and the only solution will be to replace them (Figure 3), which can get expensive at around $25 per pad. Once the pad is wet, it must stay wet throughout the day until evaporative cooling is no longer needed at night. Allowing the pad to dry out too often decreases the cooling effect and allows for increased mineral deposition on the pads as the water evaporates and minerals are left behind.

Make sure the holes in the distribution header pipe along the top of the pads remain free of debris. Regularly check them to keep them clean and open. Flush the distribution line before charging the system in the spring to remove any dirt or debris that may have accumulated during the winter. The entire pad should get wet when the distribution header pipe is operated. Dry streaks on the pad indicate a problem with uniform water distribution. Dry streaks also mean hot air is entering the house without being cooled, decreasing the effectiveness of the cool cell system. Direct sunlight on the pads and distribution line may result in excess algae growth that can plug the distribution holes or the pads. Houses today are often built with roof overhangs that cover the pads and distribution system to help reduce algae growth. Use filters on the pad system to help minimize debris that can clog the holes in the header pipe. Regularly perform preventive maintenance on these filters.

The flutes (holes) in the pads must be kept open. Flutes in the pads are notorious for collecting dust and cobwebs. Don’t make matters worse by blowing grass clippings from your mower or brush hogging toward the pads. Always aim the discharge away from the pads to keep clippings from being sucked into the flutes and restricting airflow.

Keeping the flutes open is sometimes just a matter of spraying water on them with a garden hose. Do not use bleach or any product containing chlorine to clean the pads. Strong chlorine solutions will destroy the cellulose material that most pads are made of. Do not use high pressure for cleaning because it will likely damage the pads. For extremely dirty pads, commercial products can help cut and loosen dirt. These are applied with a 3-gallon pump-up garden sprayer. However, always check the label to make sure the product is approved for use on the pads. It is recommended to maintain clean water, free of dirt and debris, in cool cell reservoirs by draining and replacing on a weekly basis or allowing small amounts to flush out when the system is running, to be made up with fresh clean water.

Heat Dissipation and Static Pressure

Birds must be able to dissipate about 12 Btu of heat per hour per pound of body weight if they are to maintain their comfort level. As the air temperature near the bird increases above what is comfortable, its ability to dissipate heat from its body surface is decreased, forcing the bird to rely more on panting to cool itself through respiratory evaporation. Panting should be avoided as much as possible. Typically, at a comfortable temperature, birds will lose about 5 Btu of heat per pound per hour from their body surface and about 7 Btu through breathing. Birds will increase their breathing rate and start panting as the air temperature rises above what is comfortable. If the air temperature reaches such a high level that panting can no longer maintain a normal body temperature, the bird’s internal body temperature will rise. This results in severe heat stress and will lead to mortality if the situation cannot be corrected with supplemental cooling.

It’s important to know what the static pressure is in the house with all the tunnel fans running. This is especially true in steel truss or high ceiling houses that have had baffle curtains installed to improve the air velocity. The static pressure should never be more than 0.12 inches. If it is, the fans have to work too hard. Many controllers today can monitor static pressure at least in one location. However, you may not know what the pressure is at various locations down the house.

It’s important to know the pressure at 20–30 feet past the pads and 20–30 feet past the last baffle curtain. The reading near the last baffle curtain will likely be higher, but it shouldn’t be too much higher. If you have a reading of 0.04 inches near the pads and 0.10–0.12 inches near the last baffle curtain, it is possible the baffle curtains are too low and need to be raised a foot or so. This should increase air velocity down the house and reduce the static pressure, relieving some of the workload on the fans and improving house conditions.

If the pressure is high at or near the pads, you have other serious problems. The pads may be dirty or clogged with mineral deposits. You will need a magnehelic pressure gauge, or a digital manometer (Figure 4) and some plastic tubing to measure static pressure in various locations throughout the house. These can usually be purchased for between $90 to $110, or your service tech may carry such items and be able to assist in checking the static pressure.

Managing Airflow

During the summer heat when in full tunnel ventilation, you want everything to be adjusted just right to maximize air speed and cooling. Just as important is to make sure your cool cell pads and fans are clean and free from obstructions; the same can be said for the tunnel inlet. It is a good idea to inspect the tunnel inlet doors or curtains and make sure all is in good shape. Sometimes ropes and cables can get hung, which can prevent the doors and curtains from properly opening. In turn, this can restrict the incoming air which will increase static pressure, hurt windspeeds, and ultimately hinder cooling. Also, you want to address any leaks you may have in the house. If you have improperly adjusted vents, broken vent strings, or any cracks and openings in the sidewall or ceiling, these are places where hot outside air enters the house and bypasses your evaporative cooling system. If you have a leaky house and can’t quite figure out where the leaks are, you may want to consider performing a smoke test to identify where unwanted air is entering the house. To perform a smoke test, you will want to close the house tight and run one fan to pull negative pressure. After pulling negative pressure, you can have someone introduce smoke to the exterior walls with a smoke bomb or generator; this will show you where the air is entering the house.

Take Advantage of Nighttime Cooling

Don’t overlook the potential for nighttime cooling. After managing the heat of daytime summer conditions, broilers need the cooler temperatures provided at night, along with ample air movement to recuperate and prepare for the next day. Running fewer fans at night may save a little electricity, but it is a lost cooling opportunity and could be costing you significant performance losses. One reason for this is relative humidity. Humidity is much higher at night (usually between 80 and 95 percent). However, even at night, regardless of air temperature, birds rely on the evaporation of water off their respiratory system to cool themselves.

High humidity makes it much more difficult for the bird to accomplish significant evaporative heat loss off the respiratory system because the air it breathes in is almost as saturated as the air it breathes out. If you maintain high air movement at night by running additional fans, you can increase the amount of heat loss and reduce the bird’s need to cool itself.

In addition, as the temperature drops at night, there is a larger difference between air temperature and the bird’s body temperature. This makes it easier for air movement to pull heat away from the bird and lower its body temperature. As its body temperature drops at night, the bird will regain the appetite it lost during the hot part of the day. However, increased feed intake will lead to increased heat production and the need to maintain increased air movement late into the night to provide optimum cooling. Obviously, running more fans later into the night will use extra electricity, but the increased bird performance should more than offset the additional power costs.

Don’t Forget the Generator

Finally, program your backup generator to exercise each week for at least 30 minutes. It is a good idea to schedule it for a time you will be on the farm to verify that it does run and record hour meter readings weekly; don’t just assume it ran. Check the fuel level regularly and keep the tank at least half full (two-thirds or more is better), this is important for two reasons: 1) in the event the generator is needed, it will have sufficient fuel to run until someone can get there and check on things, and 2) the more air space that is present in the fuel tank means there is a greater chance that moisture can become an issue. Having a sight tube or some sort of fuel gauge makes it quicker and easier to monitor fuel levels (Figure 5).

It is also wise to fully service the generator once a year and inspect before each flock. If the generator won’t start or runs out of fuel when you need it most, disaster is only a few minutes away! Summer heat and humidity are stressful on Mississippi poultry flocks and growers. Fans, cool cell systems, and emergency backups should be checked and ready long before summer heat and humidity arrive. Take every precaution to ensure that you have done all you can to protect your flocks and maximize potential summertime returns.

References

Czarick, M. (2007). What does it take to keep large broilers cool during hot weather? Poultry Housing Tips. Vol 19(11). October. University of Georgia Cooperative Extension Service.

Czarick, M. (2007). Evaluating tunnel ventilation system performance…Are you ready for hot weather? Poultry Housing Tips, Vol. 19(7). June. University of Georgia Cooperative Extension Service.

Donald, J., Eckman, M., & Simpson, G. (2002). Getting broiler houses ready for hot weather. Alabama Poultry Engineering and Economics Newsletter. No. 17. May. Auburn University.

Donald, J., Campbell, J., Brothers, D., & Simpson, G. (2012). Get ready for hot weather now. Poultry Engineering, Economics, and Management Newsletter. No. 76. March. National Poultry Technology Center, Auburn University.

Fairchild, B., & Czarick, M. (2005). The importance of nighttime wind speed during hot weather. Poultry Housing Tips. Vol. 17(8). University of Georgia Cooperative Extension Service.

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The information given here is for educational purposes only. References to commercial products, trade names, or suppliers are made with the understanding that no endorsement is implied and that no discrimination against other products or suppliers is intended.

Publication 2778 (POD-07-24)

Revised by Jonathan Moon, Extension Instructor, Poultry Science, from a previous edition by Jessica Wells, PhD, Assistant Teaching Professor, Tom Tabler, former Extension Professor, and Haitham M. Yakout, former Visiting Research Professor, Poultry Science.