Minimum Ventilation in Broiler Chicken Houses

High FCR can result in disease susceptibility and a high mortality rate. Many international companies selling ventilation equipment, conducting highly competent and serious R&D studies in their fields, as well as local brands

It's possible to find it in Türkiye. Regardless of which company's poultry equipment is used, it's essential to understand the ventilation logic and basic principles for the system to operate efficiently.

This article will discuss time-controlled ventilation systems, which share the same basic operating principle, rather than existing complex and expensive ventilation methods. TIME-CONTROLLED WINTER VENTILATION systems are an extremely easy-to-use and inexpensive ventilation method, particularly for broiler production facilities.

HOUSE WINTER VENTILATION (MINIMUM VENTILATION)

Most poultry house owners and technical keepers we ask this question will answer, "To ensure the animals' oxygen needs." However, ensuring oxygen needs is among the last priorities of minimum ventilation. The primary purpose of minimum ventilation is to maintain good air quality and maintain the desired temperature range for optimal performance. Winter ventilation also aims to remove unwanted moisture from the poultry house to ensure good litter quality.

The purposes of minimum ventilation in poultry houses are:

• Removing harmful gases such as ammonia and carbon dioxide from the chicken coop

• To remove excess moisture from the coop

• To remove excess heat produced by the chicken from the coop

• To provide the oxygen that chickens need

• To minimize dust and most importantly to SAVE FUEL in the coop while doing all of this.

Before moving on to minimum ventilation, let's take a look at the characteristics of the air we want in the chicken coop.

• oxygen > 19.6%
• carbon dioxide < 0.3%
• carbon monoxide < 10 ppm
• ammonia < 10 ppm
• relative humidity 45 – 65%

Ammonia in the Poultry House:

Many broiler producers are unaware of the losses they are losing due to high ammonia levels in their poultry houses. A common statement from all producers, especially during the winter months, is, "There's a slight odor in the poultry house, but it's not that bad."

In fact, it's very difficult to detect ammonia levels of 50 ppm or less in a poultry house by smell. Theoretically, the human nose can detect ammonia levels of 20 ppm or more. However, the crucial factor is the duration of exposure to high levels of ammonia and the resulting loss of sensitivity in our noses. In short, by the time we begin to detect ammonia, the animals are already suffering.

When ammonia levels in the poultry house are 25 ppm or higher, the cilia on the trachea surface, which help trap foreign particles, begin to lose their function. At 50 ppm or higher, some of the cilia are destroyed. This leaves the animals vulnerable to foreign substances from the outside environment. For example, because E coli bacteria from the outside cannot be trapped by the cilia and expelled, they can easily reach the necessary numbers to infect the air sacs. This ultimately leads to complex respiratory problems, and treating such infections is both difficult and expensive.

A study conducted in the 1960s found that the incidence of ND and IB infections doubled in animals exposed to 20 ppm or more of ammonia for 72 hours. Considering the economic losses, farms exposed to 50 ppm or more of ammonia experienced a decrease in live weight of approximately 220 grams and an increase in FCR of 8 points.

In poultry-raised flocks, assuming ventilation fans are completely stopped, ammonia levels increase by 1-4 ppm per minute, but when ventilation is initiated, ammonia levels decrease by approximately 5 ppm per minute. In other words, ammonia removal from the broiler house is faster than its formation. With adequate ventilation, ammonia levels within the house can easily be brought to the desired level.

Humidity in poultry houses:

Everyone knows that the amount of water consumed increases with the amount of daily feed consumed. Let's illustrate with an example how important minimum ventilation is in removing this water from the poultry house. Let's assume we've started production with 25,200 chicks in a 1,400 m² broiler house with an average bird density of 18 birds per m².

Assuming a final production performance of 2,200 g live weight, 1.83 FCR, and 4.8% mortality, this herd will consume 79,024 tons of feed by the end of the season for a total live weight of 43,902 kg.

If we consider that water consumption is 1.8 times the feed consumed, the amount of water entering the poultry house by the end of the season will be 142.2 tons. Based on the fact that chickens have a 75% body water content, this means that approximately 32,900 tons of water will be removed from the poultry house by the time the animals are sent to slaughter (43.902*0.75=32.900 tons). Therefore, the amount of water remaining in the poultry house and requiring ventilation will be 142.2-32.9=109.3 tons. This amount means the poultry house will be covered with approximately 8 cm of water.

WINTER VENTILATION IN BROILER HOUSES

During the winter, the humidity level outside the coop is close to 100%. It's impossible for air already saturated with moisture to be drawn directly into the coop and bind the humidity within the coop to itself.

The air outside the coop is like a wet sponge. To bind the water on the coop floor, this sponge must first be dried. The only way to achieve this is to warm the cold air entering the coop. The warm air inside the coop collects in the roof space.

As seen in the thermal photo, the heated air in the coop (red area) is collected in the roof space. This heat is utilized during winter ventilation.

Air drawn into the house by fans is forced along the roof, under sufficient pressure (the pulling force that draws the air entering the house towards the center), and is then transported to the center of the house. Both during this journey and as a result of mixing with the warm air in the center of the house, the heated air's density decreases, increasing its ability to hold water. In other words, the wet sponge dries and regains its ability to hold water.

For every 10°C increase in the temperature of the air taken into the chicken coop from the outside environment, the water retention ability doubles.

Dry and warm air is brought down to the level of the animals and is expelled from the poultry house by binding the heavy, moist and dirty air at the level of the animals.

In a 16-meter-wide poultry house, heavy, cold air entering from outside must travel approximately 8 meters to the center of the house to reach the desired temperature. This movement can only be achieved by creating sufficient static pressure from the fans operating within the house.

In order to obtain sufficient static pressure;
• Fans and draft capacities must be sufficient
• To prevent air leaks, there should be no uncontrolled air inlets (windows, doors, tunnel fan edges, etc.) in the poultry house
• There must be air inlet vents with an appropriate number and surface area. (air dampers)

How to measure static pressure in broiler house?

Electronic instruments can be developed to measure the traction force generated by the operation of fans within the poultry house. However, because such instruments are both difficult and expensive to procure, widespread use is quite difficult, especially for broiler farms. The only materials needed to measure the traction force within the poultry house are a 4-5mm diameter IV hose, approximately 1-1.5 m long, and a container filled with water.

Measuring static pressure in the poultry house:

All air inlets and fans in the house are closed. One end of the serum tube is left inside the house, while the other end is brought out through a small hole and immersed in a container filled with water. The water level is marked on the serum tube.
In the next stage, one 33,000 m³ tunnel fan or two 16,500 m³ fans (one at the end of the house and the other at the front) are operated inside the house. Due to the pulling force (negative pressure) created by the operation of the fans, the water level in the serum tube, located in the container outside the house, should increase.

If this value is at least 3-3.5 mm (0.13 inch = 34 pascals), the enclosure/airtightness of our house is sufficient, and when the fans start operating, the necessary draft can be created to draw the cold air into the house center. In newly constructed houses, this value should be 5-6.5 mm (0.20-0.25 inch) or 50-60 pascals. (M. Czarick, University of Georgia. Operating modern broilerhouses during the coldweather).

MINIMUM VENTILATION FANS IN POULTRY CAGES

Implementing minimum ventilation with tunnel fans is quite difficult. In minimum ventilation with tunnel fans, air enters the house in very high volumes through a relatively small point (the air inlet). As a result, air is drawn into the house before it reaches the roof, mixes with hot air, and heats up. The incompletely heated air falls on the birds, creating a cooling effect. Minimum ventilation fans are smaller in capacity than tunnel fans and are mounted on side walls or roofs. In farms where minimum ventilation fans are not available, larger-capacity tunnel ventilation fans can also be used, although they are not as practical and difficult to implement as smaller fans.

ANIMAL AIR INTAKE VENTS (BALLS, AIR FLAP, MOANS)

Air inlets must be provided in sufficient numbers and with sufficient space to ensure that the air taken into the house reaches the center of the house. As the house width increases, the distance the air must travel increases, and the air speed entering the inlets must increase.

However, in practice, 3.5-4.5 m/sec is sufficient when calculating the speed of air entering from the vents.

Example: Let's assume that the total power of the fans to be used for minimum ventilation in a farm with a 16 m wide poultry house is 60,000 m³.

In a 16-meter-wide poultry house, the required air velocity at the vent to bring air from the outside to the center should be 4-5 m/s, as previously mentioned. Let's take 4.5 m/s as a median value.

Total vent (Baffle, Air Damper) area (m²): 60,000 / 3600*4.5 = 3.70 m²

Let's assume that the air valve size is 25 cm height and 50 cm length.

Total number of Air Dampers: 2.78/ (0.25×0.50)= 29.6
(Approximately 30 pieces)

A total of 30 vents, each 25cm high and 50cm long, will be distributed 15 at equal intervals on the side walls to ensure that the desired amount of air is taken into the chicken coop at the desired speed.

Poultry ventilation valve openings

Modern ventilation systems can automatically increase or decrease the air damper openings depending on the fan speed or the force of the fan operating to maintain air velocity in the ventilation inlets. The goal is to maintain the necessary static pressure within the house to achieve the air velocity in the vents, regardless of the varying air volumes needed at different ages by adjusting the air damper openings. This allows for the transfer of cold air from the outside to the center of the house.

In timed-controlled systems, the air inlet, which will open automatically or manually when the fans start operating, should have an optimum opening of 5-7 cm. The conditions inside the chicken coop are monitored by a computer or a keeper, and the appropriate opening ratio is determined.

GOLDEN RULES IN WINTER VENTILATION IN BROILER HOUSES

• Any unwanted openings that may negatively affect the proper ventilation of the chicken coop and cause air leakage should be closed.

• In order to keep the warm air we obtain at high costs in the winter season inside the coop and to ensure good ventilation, great importance should be given to the insulation of the coop.

• To provide the most appropriate ventilation for the age of the flock in the coop, the fan operating speed should be adjusted to the most appropriate rate.

• The fan's operating time should be increased regularly on a weekly basis from the time the chick enters the coop until the end of the brooding period.

• To ensure the desired air quality within the poultry house, heaters should operate independently of the minimum ventilation fans. Regardless of the internal or external temperatures, the established ventilation settings should be applied. Even if the temperature inside the poultry house falls below the desired value, the minimum ventilation fans should operate at the established rates.

• Cold air taken into the chicken coop from the outside should be taken in from the top, avoiding direct contact with the animals, and should be mixed with hot air and heated before reaching the animals.

• If there is humidity in the chicken coop or if the amount of ammonia in the coop is high, minimum ventilation rates should be increased.

• If the ammonia or litter problem has not decreased even though minimum ventilation has been increased, the coop should be heated for a while.

• Situations where the poultry house is very dusty or dry indicate that excessive ventilation is taking place and in this case ventilation rates should be reduced.

• If the temperature inside the chicken coop is high, the thermostat settings should be checked rather than the fan operation settings.

MINIMUM WEEKLY VENTILATION REQUIREMENT IN POULTRY CAGES

The minimum weekly ventilation values ​​per animal required to ensure air quality in broiler houses are as follows.

Minimum weekly ventilation requirements for the coop are calculated based on the total number of chickens (chickens) in the coop. Minimum ventilation requirements may vary depending on the climatic conditions of the area where the coop is located and the desired air quality within the coop.

Adjusting the Fan Operating Time According to the Age of the Flock in the Coop

The minimum ventilation time is 300 seconds or 5 minutes. This means that the total of the ventilation fan operation and the subsequent pause time must be 5 minutes.

Example:
Let's assume we have 5 minimum ventilation fans, each with a capacity of 12,000 m³, in our 20,000-egg broiler house. Let's calculate the weekly minimum ventilation amounts we need.

In order to provide sufficient static pressure inside the chicken coop, we need to start ventilation with at least 3 fans
(Note: Let's remember that we need a draft of at least 33,000 m³/h to obtain the required static pressure inside the chicken coop).

In the 3rd column, the minimum weekly ventilation values ​​required for a 20,000-piece broiler house are given.

While the ventilation value we need for the 3rd week is 12,000 m³/hour, the total power of our 3 operating fans is 12,000×3= 36,000 m³/hour.

The ventilation rate we need is only 33% of the total power of three fans, each producing 12,000 m³/h. If we apply the same ratio to the fan runtime, the ventilation fans should also operate at 33%. Calculating this ratio based on 300 seconds, the fans' runtime will be 100 seconds, while the stop time will be 300 seconds - 100 seconds = 200 seconds.

In the farm given in this example;
3 fans, each with a capacity of 12,000 m³/hour, will be operated for 24,000 broilers aged 3 weeks, operating for 100 seconds and stopping for 200 seconds, ensuring the minimum ventilation required by the flock and adequate air quality inside the poultry house.

• To ensure more uniform temperature distribution within the poultry house, a larger number of smaller-capacity fans should be preferred over a small number of large fans. Instead of a single fan with a capacity of 36,000 m³/hour, three fans, each with a capacity of 12,000 m³/hour, will yield better results.

• In order to save fuel, the working time should not be more than half of the total time (300 seconds) (more than 150 seconds).

• As the chickens grow older, they will emit more heat, humidity and harmful gases into the environment, so the weekly working hours should be increased to meet the minimum ventilation requirement.

• If there is a wet litter or ammonia problem in the poultry house, working rates should be increased.

Light ammonia: + 15 seconds
Heavy ammonia: + 30 seconds
High Humidity: + 15 seconds
High Dust: – 15 seconds

•To roughly gauge the humidity of the litter in a coop, simply squeeze it. If it doesn't stick together and form a ball, it's moist. If it sticks slightly and softly, it's sufficiently moist. If it doesn't, it's dusty and dry.

• If the litter surface is slippery and damp, increasing fan operation may not be enough to solve the problem. In this case, an additional heater is generally required to reduce the moisture and facilitate its removal. Humidity inside the coop can be reduced by increasing the fan operation during the hottest hours of the day. If this is not sufficient, an additional heater should be added.