Poultry House Healthy Ventilation

Correct airflow is fundamental to a healthy and productive poultry flock. Here, we review the basic steps to achieving fresh air at the right temperature.
Poultry House Healthy Ventilation (1)

Ventilation is one of the most crucial elements in broiler welfare and production.
The right system not only ensures adequate air exchange throughout the broiler house, but also removes excess moisture from the litter, maintains oxygen and carbon dioxide levels, and regulates temperature within the house.

Aims and legislation
Legally there are certain air quality requirements that a ventilation system must be able to provide.

Dust particles
Humidity <84%>
Ammonia
Carbon dioxide <0.5%>
However, the aims for air quality should go beyond the basic legal requirements and look to providing the best environment possible for bird welfare, health and production.

Ventilation System Types
By far the most common set-up in the Southeast Asia is a ridge-extraction, side-inlet system.
Fans sited in the roof apex draw warm, moist air up through the house and out through the ridge. Removing the air creates negative pressure in the airspace, drawing fresh cool air in through the inlets mounted along the side of the house.
Side extraction systems, which removed air through the sides of the housing, became effectively obsolete with the introduction of Integrated Pollution Prevention and Control (IPPC) legislation. Side extraction systems fell afoul of the law because dust and debris drawn out of the house was ejected at too low a height.

Poultry House Healthy Ventilation (2)

Likewise, cross ventilation systems which drew air in on one side, across the top of the flock and then vented it on the opposite side, also contravened the IPPC rules.

The only other system which is currently in use in the Southeast Asia is tunnel ventilation. This draws air in high up in the gable end, along the ridge and out through the opposing gable. It is less efficient than the commonly used ridge extraction system and largely confined to being an additional source of airflow in high temperatures.

Poor ventilation signs
Monitoring equipment and comparison of graphs from data collected on temperature and air quality should provide an early warning of anything awry. Key indicators such as changes in water or feed intakes, should spark investigation of the ventilation system.

Aside from the automatic monitoring, any problems with the ventilation system should be detectable from the atmosphere in the broiler house. If the environment feels comfortable to stand in then it is very likely that the ventilation system is working well. But if the air feels uncomfortably muggy or close and there is a smell of ammonia, then temperature, oxygen and humidity levels must be investigated straight away.

Other tell-tale signs include sporadic bird behaviour such as an uneven flock distribution across the floor of the house. Clustering away from parts of the shed or birds that are hunkered down could indicate that the air is not being circulated properly and cold air spots have formed. If the conditions are left to continue birds may start to show respiratory difficulties.

In contrast when birds are too hot they may move apart, pant or raise their wings. Reduced feed intake or a spike in water consumption can also indicate a shed is too hot.

Maintaining control as conditions change
For the first few days after placement ventilation should be set to promote higher relative humidity levels between 60-70%. This allows mucus membranes in the respiratory tract to develop. Too low a level and the pulmonary and circulatory systems may be affected. After this initial period, humidity can be lowered to 55-60%.

Aside from age the biggest influence on air quality are the conditions outside the housing. Hot summer weather and freezing conditions in the winter must be controlled by the ventilation system to achieve an even environment inside the shed.

Summer
An increase in body temperature of 4°C can cause fatalities, but many of the deaths attributed to hot weather are when humidity rises in tandem with temperature.

To lose body heat birds pant but the physiological mechanism requires abundant fresh, dry air. So, when temperatures exceed 25°C in summer, it is important to deliver as much fresh air at bird height as possible. This means setting inlets to a wider opening, to direct cool air lower down.

As well as roof extraction, it is possible to install fans in the gable ends of a building. For most of the year these fans remain unused but if temperatures rise the additional capability kicks in and can quickly bring conditions back under control.

Winter
In contrast to summer controls, it is important to stop cold air accumulating at flock height when the temperature cools. When birds are cold, growth rates slow down and welfare can be compromised by other health issues such as hock burn. Hock burn occurs when bedding becomes wet due to condensation in cold air accumulation at low levels.

Inlets in the winter should be narrowed so that air comes in at a higher pressure and angled to force airflows upward and away from directly chilling the flock at floor level. Closing up side inlets to ensure cold air is forced along the ceiling towards the roof fans means that as it drops it loses some of its humidity and heats up before reaching the floor.

Heating further complicates the picture in the winter, particularly with older systems. Although higher temperatures can help reduce excess moisture, gas heaters use up about 15l of air to burn 1l of propane while producing CO2 and water. Opening the ventilation to remove these can in turn bring in cold, moist air which requires further heating so creating a vicious cycle, and the ventilation system starts to fight itself. For this reason, modern systems function using more sophisticated software that creates margins around measurements of CO2, ammonia and moisture. The degree of flexibility means the system gradually levels these elements out rather than making knee-jerk reactions one after another.


Post time: Sep-06-2021