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Broiler-house management is key to preventing winter respiratory disease

website builder By Tak Niino, VMD
Technical services veterinarian
Zoetis Inc.


Respiratory disease in broilers can occur any time of year, but it’s especially problematic in winter months, when air and environmental conditions may become compromised as producers try to keep costs under control.

Maintaining good air quality is essential and is heavily influenced by ventilation techniques. When a house is underventilated, ammonia levels and litter moisture can rise to the point where they’re detrimental to the health of birds, predisposing them to respiratory disease.

Elevated ammonia levels damage the cilia, those brush-like structures responsible for clearing debris out of the trachea. When the cilia are damaged or destroyed, birds may succumb to viral infections such as infectious bronchitis (IB), infectious laryngotracheitis (ILT) or Newcastle disease (ND). These viral pathogens can also cause ciliostasis, which can result in chickens displaying signs of lethargy, depression or coughing and snicking.

Poor litter quality due to inadequate ventilation is favorable for bacterial growth. That’s why it’s not uncommon for birds that have a respiratory virus to develop a secondary bacterial infection — usually Escherichia coli — which can lead to severe polyserositis, septicemia and even death.

Evidence of respiratory disease can show up at the processing plant as well as in the poultry house. Condemnation due to airsacculitis, often due to an underlying respiratory disease, may trend upward during cooler months, when maintaining an optimal environment becomes a challenge. An increased number of birds with airsacculitis can affect the efficiency of the processing plant. More birds will have to be rerouted and salvaged for parts, which can slow the line speed, and that’s costly.

Bigger houses, aging equipment

One trend that may influence ventilation practice is variation in house size. Today, many poultry growers are choosing to build larger houses in an effort to efficiently raise more birds. However, the methods traditionally used to ventilate smaller houses may not yield the same results in larger houses. Care must be taken to ensure that longer and wider poultry houses have the proper equipment and ventilation settings necessary to adequately move and exchange air. Air has to travel further and if airflow is uneven, birds at one end of the house might have fresh air, while birds at the other end don’t.

Poorly maintained equipment is another problem that can lead to difficulty heating and ventilating the house. Old and unmaintained fans might still run, but that’s no guarantee that the cubic feet of air moved per minute is the same as it was when the fans were first installed. A fan may not be capable of moving the intended amount of air if shutters are dirty and belts need replacing. Air flow can be easily monitored using an air flow meter. Proper and regular maintenance is critical to make sure the systems are working properly.

Computerized, automated systems with preset programs are handy and can work well if used appropriately. Advancements in farm equipment make it easy for growers to monitor the house condition and ventilation settings without having to enter the house. However, never assume birds are comfortable just because the computer indicates everything is running smoothly. There is no one-size-fits-all setting since the conditions for keeping birds comfortable and healthy can vary flock to flock. Because of this, it’s important to look at the birds regularly to make sure they are comfortable. Visually checking birds is a fail-proof way to confirm that house conditions, including ventilation and litter quality, are appropriate.

Monitor ammonia

As for ammonia levels, those of us who spend a lot of time in poultry houses can easily become desensitized to the smell and may not realize ammonia levels are too high for bird health. A highly sensitive human nose is capable of detecting ammonia at a concentration as low as 1 ppm; however, I have been inside houses where ammonia levels exceeded 20 ppm but were unnoticed by the grower. For poultry, it’s imperative to keep levels below 25 ppm to prevent a loss in performance and increase in disease — and to protect the safety of workers.

Ammonia levels should be monitored routinely throughout the life of the flock, and if they’re too high, ventilation settings must be adjusted to reduce the ammonia concentration. There are a number of different tools available for evaluating ammonia levels. Whichever tool you choose to use is fine as long as it yields consistently accurate results.


A vaccine program tailored to help protect against respiratory disease risks is essential and should be individualized, taking into account risks on the farm and in the geographic area.

Infectious bronchitis virus (IBV), for example, is always a concern for broiler flocks, and the key to protection is identification of the IBV strain that’s circulating. Diagnostic methods such as serology, hemagglutination inhibition and polymerase chain reaction analysis can determine the most prevalent IBV serotypes in a flock. Sometimes a heterologous program — using vaccines with different serotypes — may help provide cross protection in the field.

Producers in the Southeast US will need to determine if their flocks need protection against IBV strains such as Georgia 08, a particularly damaging IBV variant, whereas in the Northeast, Delaware 072 can be of concern. Along with IBV, other respiratory pathogens such as ILT and ND may be a problem based on region and time of year. Proper vaccination programs play a major role in helping to provide protection against these diseases.

Some US broiler producers with elevated condemnations due to secondary E. coli infections are evaluating the use of a modified-live, non-reactive E. coli vaccine. The vaccine has been credited with a marked reduction in E. coli-related mortality in layers,1 and field trials with the vaccine in broilers here and abroad have been promising.2-4

In short, vaccination along with managing the environment is crucial for maintaining bird health. For many growers, desirable ventilation can be challenging in cooler months, especially in light of high fuel costs. However, inadequate ventilation puts birds at risk for respiratory diseases that can lead to high rates of morbidity and condemnation. As a result, initiating good management and a solid vaccination plan are often more cost effective in the long run — and spare producers from a lot of headaches.





Editor’s note: The opinions and recommendations presented in this article are the author’s and are not necessarily shared by the editors of Poultry Health Today or its sponsor.



1. Shane, SM. Reducing pathogen E. coli infection by vaccination.  Broilers. World Poultry. Updated October 14, 2010.  http://www.worldpoultry.net/Broilers/Health/2009/12/Reducing-pathogenic-E-coli-infection-by-vaccination-WP006966W/ Accessed September 25, 2015.

2. Cookson K, Davis S, et al. Cross protection study of a modified live E. coli vaccine against three heterologous APEC serotypes in commercial broiler chickens. In: Proceedings of the 58th Western Poultry Disease Conference; 2009 March; Sacramento,CA. p. 60-62.

3. Cookson K, Macklin K, et al. The efficacy of a novel live E. coli vaccine using a broiler skin challenge model. Abstract 1568. In: Proceedings of the 23rd World’s Poultry Congress; 2008 July; Brisbane, Australia.

4. Cookson K, Sasipreeyajan J, et al. Efficacy study of a live E. coli vaccine in broilers against three field isolates from Thailand. In: Proceedings of the 59th Western Poultry Disease Conference; 2010 April; Vancouver, BC, Canada. p. 70-72.






Posted on December 15, 2017

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The complementary effect of two new vaccines provides immunity against infectious bursal disease virus (IBDV) – one of the major threats to commercial flocks worldwide.

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