In late autumn and early winter, a light rain or a gust of northerly wind can cause temperatures to plunge by more than ten degrees. For layer farms, this is the most challenging and critical time of year for environmental control. Poor ventilation management can cause stress in the flock, fluctuations in egg production rates, and an increase in the feed-to-egg ratio; in more severe cases, it can trigger respiratory diseases and result in significant economic losses. Therefore, it is crucial to accurately understand the key ventilation management points for late autumn and early winter.
一、Seasonal Characteristics of Late Autumn and Early Winter
The main climatic characteristics of late autumn and early winter are large day-to-night temperature differences and dramatic fluctuations in humidity. Therefore, the management priority for layer farms during this period is to resolve the conflict between heat retention and ventilation.
Heat retention reduces the energy the flock expends maintaining its body temperature, allowing more of that energy to be used for egg production. Ventilation is intended to remove harmful gases in the poultry house (such as ammonia, hydrogen sulfide, and carbon dioxide), excess moisture, and dust, while supplying fresh oxygen. During cold seasons, staff often reduce ventilation out of fear that the flock will “catch a chill,” causing indoor air quality to deteriorate sharply. In fact, a hot, humid environment with a pungent ammonia odor is much more harmful to the flock than the cold stress caused by moderately low temperatures. Therefore, the core of layer farm management in late autumn and early winter is “how to keep temperatures as stable as possible while ensuring the minimum ventilation rate.”
二、 Key Ventilation Management Points for Late Autumn and Early Winter
1, Establish and Follow a “Minimum Ventilation Mode”
Minimum ventilation refers to the minimum airflow required to maintain air quality inside the poultry house at the lowest acceptable standard (e.g., ammonia <20ppm, relative humidity 55%-65%) while keeping doors and windows closed and ensuring the house is basically sealed. Minimum ventilation is usually calculated based on the chickens’ body weight and the number of birds in the house. Basic calculation formula: minimum ventilation = number of chickens in the house × average body weight (kilograms) × ventilation coefficient (the ventilation coefficient varies by region and chicken age and should be determined according to the actual conditions of the farm). When selecting fans, one or more “minimum ventilation fans” (usually smaller fans) must be used. Avoid using large fans for short, powerful extraction cycles, as this will cause sharp temperature fluctuations and waste energy.
2, Precise Control of “Negative Pressure” and “Air Velocity”
Negative pressure is the driving force behind ventilation in a sealed poultry house. It determines the direction, speed, and mixing effect of fresh air entering the house.
Negative pressure management: In late autumn and early winter, negative pressure needs to be adjusted accordingly as the size of the ventilation window openings is adjusted. The principle is to ensure that incoming cold air has enough momentum to reach the central roof area of the house, mix thoroughly with the warm air near the ceiling and warm up, then descend evenly and slowly to the level where the chickens are active. If negative pressure is too high, airflow moves too fast and may create “drafts”; if negative pressure is too low, the airflow does not travel far enough, and cold air falls directly, causing the chickens to become chilled.
Prevent “drafts” at all costs: Drafts are localized, fast-moving, low-temperature airflows and are the primary cause of colds in chickens in winter and a leading trigger of diseases such as mycoplasmosis and Escherichia coli infection. Carefully inspect the seals around the poultry house walls, doors and windows, cooling pads, and small air inlets, and seal all gaps. Ensure that the openings of the small air inlets are the same size and that the deflector angles are correct, so that cold air is discharged in a “parabolic” trajectory.
3, Coordinated Temperature and Humidity Management
Perceived temperature is key: What the chickens feel is the “perceived temperature,” not the “actual temperature” shown by the thermometer. Perceived temperature is affected by both air velocity and humidity.
Humidity control: The target is to keep relative humidity at 55%-65%. When humidity is too high, the chickens will feel cold and damp even if the temperature is on target. In this case, increase minimum ventilation appropriately to remove moisture. When humidity is too low, consider using an in-house misting system (not a humidifying cooling pad) or reducing ventilation appropriately to increase humidity.
4, focus on switching between “transition ventilation” and “tunnel ventilation”
In late autumn, daytime temperatures may still be relatively high, so “transition ventilation” may need to be activated for cooling. At night, however, it must be switched back to “minimum ventilation.” Setting this changeover point is crucial. If the set temperature is too high, daytime ventilation will be insufficient; if it is too low, there will be excessive ventilation at night.
Three. Management essentials for layer farms in late autumn and early winter
Observe frequently: Managers should enter the poultry house several times each day—morning, midday, and evening—to assess air quality using their senses. They should also record key data such as temperature and humidity, negative pressure, and fan operating time to facilitate analysis and traceability.
Transition gradually: Switching from the autumn mode to the winter mode cannot be done all at once. As outdoor temperatures steadily decline, gradually reduce ventilation and narrow the air inlets, allowing the flock time to adapt.
Pay attention to routine equipment maintenance: Before the cold season arrives, the ventilation system must undergo a comprehensive inspection and maintenance. Clean the fan blades and louvers to ensure operating efficiency; calibrate the temperature and negative-pressure sensors; and inspect and lubricate the motors and linkages of the small air-inlet windows to ensure they open and close smoothly and in sync.
As the scale of farming continues to grow, intelligent environmental control systems have been adopted by thousands of farms. By systematically monitoring outdoor temperature and indoor temperature, relative humidity, wind speed, and air quality, and adjusting fan operation at any time according to the flock’s minimum breathing requirements, these systems help keep poultry-house temperatures stable and the air fresh, thereby protecting the flock’s health to the greatest extent possible.