Summer heat poses a critical threat to layer chicken farming. When temperatures in layer houses consistently exceed 28°C, hens are prone to heat stress, leading to reduced feed intake, sharp declines in egg production (by 15%-30% in severe cases), poorer egg quality (more thin-shelled or misshapen eggs), and even heatstroke-related mortality. Traditional cooling methods, such as standalone fans or spraying systems, often suffer from low efficiency or uncontrolled humidity. In contrast, the combined "ventilation fan + cooling pad" system leverages dual mechanisms—wind-chill cooling and evaporative cooling—to precisely regulate temperature and humidity in layer houses, making it a mainstream solution for modern large-scale poultry operations.

I. The Lethal Logic of Heat Stress: How High Temperatures Destroy Egg Production

The physiological traits of layer hens make them highly vulnerable to heat:

1. Limited Thermoregulation

Hens lack sweat glands and primarily rely on panting to dissipate heat. When temperatures surpass 30°C, their breathing rate soars from 20–30 breaths per minute to over 100, causing excessive loss of carbon dioxide (CO₂) and triggering respiratory alkalosis. This directly suppresses their appetite and central feeding drive.

2. Metabolic Disruption

Under heat stress, hens prioritize energy expenditure on thermoregulation over egg production. For every 1°C rise in temperature, feed intake drops by 3–5 grams, reducing protein synthesis and stalling follicular development, which leads to lower egg production rates.

3. Humidity-Amplified Harm

When humidity exceeds 70%, evaporative cooling efficiency plummets. Even at 28°C, hens struggle to shed heat, exacerbating stress and increasing mortality.

Core Conflict: Single cooling methods fail to address both high temperature and high humidity simultaneously. The "ventilation fan + cooling pad" system overcomes this by combining physical cooling mechanisms.

II. The Dual Power of the Synergistic System: Wind-Chill + Evaporative Cooling

1. Ventilation Fans: Creating Negative Pressure Airflow for Forced Ventilation

Mechanism:

Negative pressure exhaust fans (typically installed at one end of the house) expel hot indoor air, generating a negative pressure zone that draws in outdoor air through cooling pads, creating directional airflow.

Key Parameters:

Airspeed Control: Airflow inside the house should reach 1.5–2.5 m/s to ensure full coverage of the hens’ bodies, creating a wind-chill effect (equivalent to a 3–5°C temperature drop).

Air Exchange Rate: The house should achieve 15–20 complete air exchanges per hour to rapidly remove harmful gases like ammonia and CO₂, preventing stuffiness.

2. Cooling Pads: Evaporative Heat Absorption to Lower Inlet Air Temperature

Mechanism:

Cooling pads (usually honeycomb-structured paper or polymer materials) are soaked in water. As air passes through, water evaporation absorbs heat, reducing incoming air temperature by 5–8°C.

Scientific Advantages:

Humidity Balance: Evaporation naturally increases air humidity (from ~40% to 60–70%), but forced ventilation prevents excessive accumulation.

Uniform Cooling: Pads cover the entire air inlet, ensuring consistent temperature reduction across the house and avoiding localized hot/cold spots.

3. Synergistic Effects: 1 + 1 > 2 Cooling Logic

Temperature Gradient Control:

Ventilation fans distribute cooled air (e.g., 30°C → 25°C) evenly throughout the house while expelling hot air, maintaining a "cool-in, hot-out" cycle.

Dynamic Humidity Regulation:

When outdoor humidity is low (<60%), cooling pads achieve high evaporation efficiency; when humidity is high, ventilation fans enhance airflow, using wind-chill to compensate for reduced evaporative cooling and prevent闷热 (stuffy heat).

Energy Efficiency:

Compared to air conditioning, the system reduces energy consumption by 60–70% and does not require a sealed environment, making it ideal for open or semi-open layer houses.

III. Golden Rules for System Design: Precision Optimization from Parameters to Layout

1. Equipment Selection: Matching House Size and Climate Conditions

Fan Capacity:

Calculate required airflow based on house volume (Formula: Airflow = House Volume × Air Exchange Rate). For example, a 100m (L) × 12m (W) × 3m (H) house needs ≥54,000 m³/h exhaust capacity (≈3–4 × 1.4m-diameter negative pressure fans).

Cooling Pad Area:

Pad area should be ≥1.2× the total exhaust fan inlet area to ensure full air-cooling medium contact. For example, if exhaust inlets total 10㎡, pads need ≥12㎡.

2. Layout Principles: Avoiding "Cooling Dead Zones"

Air Inlet Design:

Cooling pads must uniformly cover the entire inlet (e.g., side or end walls) to prevent airflow short-circuiting. Inlets should be 1.5–2m above ground to avoid direct cold drafts on hens.

Airflow Guidance:

Install deflectors inside the house to direct cool air diagonally from the roof toward the center, then downward via ground-level airspeed, creating an "upper-supply, lower-return" circulation pattern for even temperatures.

3. Smart Control: Dynamic Adjustment Based on Environment

Temperature-Humidity Linkage:

Use sensors to monitor indoor temperature (T) and humidity (H) and automate equipment based on thresholds. For example:

If T ≥ 28°C and H < 70%, activate both fans and pads;

If T ≤ 25°C or H ≥ 80%, turn off pads and keep fans running.

Variable Frequency Regulation:

Employ variable-speed fans to adjust rotation based on temperature (e.g., increase speed by 10% per 1°C rise), avoiding excessive airspeed that stresses hens.

IV. Real-World Results: Data Proving the System’s Value

A comparative trial at a 10,000-hen farm showed:

House Temperature: Summer peak temperatures dropped from 34°C to 28°C (6°C reduction), with humidity stabilized at 65–70%.

Egg Production: Increased from 78% to 85%, extending peak production by 4 weeks.

Mortality Rate: Fell from 12% to 5%, primarily due to fewer heatstroke and respiratory disease cases.

Energy Costs: Electricity expenses decreased by 40%, and water usage by 25% (due to higher evaporation efficiency) compared to traditional spray cooling.

Key Insight: By combining physical cooling and airflow management, the system addresses both temperature and humidity, creating a more stable physiological environment for hens.

V. Common Pitfalls and Solutions: Maximizing System Efficiency

Pitfall 1: Neglecting Cooling Pad Cleaning, Leading to Bacterial Growth

Consequence: Bacteria enter the house via airflow, causing respiratory diseases.

Solution: Rinse pads weekly with 0.1% sodium hypochlorite solution, dry thoroughly, and replace aging pads every 2–3 years.

Pitfall 2: Insufficient Fans, Failing to Meet Airspeed Targets

Consequence: Cool air doesn’t reach all areas, leaving some hens heat-stressed.

Solution: Calculate airflow needs based on house volume and err on the higher side; regularly check fan belt tension to maintain exhaust efficiency.

Pitfall 3: Poor House Sealing, Causing Cool Air Leakage

Consequence: Reduced cooling efficiency and higher energy costs.

Solution: Seal gaps in doors, windows, and walls with foam or weatherstripping; install adjustable louvers at inlets to prevent leaks.

Conclusion: Scientific Cooling for a Productive Summer

The "ventilation fan + cooling pad" system mimics natural wind and rain to create an optimal microenvironment for layer hens, balancing temperature and humidity with precision. Its value lies not only in boosting egg production and reducing mortality but also in minimizing antibiotic use through better environmental control, promoting sustainable poultry farming. For farmers, this strategy is both a technological shield against heat and an invisible lever for profitability.