In the laying hen industry, layer cages with a stacked (multi-tier) design have become the mainstream choice for large-scale farming due to their high space efficiency, ease of management, and reduced disease transmission risks. However, the conflict between animal welfare concerns (such as limited movement, behavioral suppression, and skeletal health risks) and egg production rates in high-density environments remains a critical challenge. Striking a balance between "efficient production" and "animal well-being" within confined spaces has become the core focus of cage design innovation.

I. The Double-Edged Sword of High-Density Farming: Efficiency vs. Welfare

Stacked cages maximize floor space by vertically stacking 4–6 tiers, allowing a single poultry house to accommodate tens of thousands of hens. While this design significantly improves land and resource utilization, it also introduces the following issues:

1. Restricted Movement Space

Traditional stacked cages allocate only 400–500 cm² per hen (roughly the size of an A4 sheet), preventing natural behaviors like stretching wings, jumping, or dust bathing. Prolonged confinement leads to stress, frustration, and abnormal behaviors.

2. Skeletal Health Risks

Lack of exercise accelerates calcium loss in bones (especially legs and keel), increasing the prevalence of osteoporosis. Severe cases may result in paralysis or higher mortality rates.

3. Environmental Control Challenges

High stocking density demands precise ventilation, temperature, and humidity management. Localized ammonia buildup or temperature fluctuations directly impact feed intake, egg production, and egg quality.

4. Aggressive Behavior Escalation

Crowded conditions exacerbate pecking disorders (e.g., vent pecking, feather pecking), leading to injuries and infection risks.

Core Conflict: Expanding cage size reduces stocking density and profitability, while maintaining current designs risks compromising welfare—ultimately affecting long-term productivity and egg quality.

II. The Art of Balance: Optimizing Cage Design for Welfare and Efficiency

Resolving this conflict requires scientific cage designs that "maximize welfare needs within spatial constraints." Key optimization directions include:

1. Spatial Allocation: Granting Hens "Just Enough Freedom"

Increased cage area:

Modern designs gradually expand per-hen space from 400 cm² to 500–600 cm², while raising cage height (from 40 cm to ≥50 cm) to allow natural standing, head-raising, and brief wing flapping.

Optimized tier spacing:

Increasing vertical clearance between tiers from 30–35 cm to 40–45 cm prevents fecal contamination of lower tiers and reduces headspace pressure.

Sloped wire flooring:

A 5–8° incline enables eggs to roll gently into collection troughs, minimizing egg damage and pecking.

2. Behavioral Enrichment: Mimicking Natural Environments

Perches and dust bathing zones:

Foldable perches (occupying 1/3 of cage width) satisfy roosting instincts, while periodic access to shared dust bathing areas (2–3 times weekly) helps feather maintenance and parasite control.

Pecking toys:

Suspended movable objects (e.g., plastic ropes, corn cobs) divert attention and reduce pecking disorders.

Dark retreats:

Shaded corners provide "privacy zones" for timid hens to escape conflicts, lowering stress levels.

3. Health Management: Details Drive productivity

Upgraded flooring materials:

Hot-dip galvanized wire or plastic grids prevent rust contamination; optimized mesh size (3 cm × 6 cm vs. 2.5 cm × 5 cm) reduces toe injuries.

Drinking system refinement:

Nipple drinkers (1 per 10 hens) with pressure regulators ensure clean water access without leaks.

Egg collection buffers:

Soft rubber pads at trough ends minimize egg collision damage, reducing breakage rates from 3% to <1%.

4. Environmental Control: Creating comfortable microclimates

Ventilation optimization:

Deflectors on cage tops/sides distribute fresh air evenly, keeping ammonia levels <15 ppm.

Zoned climate control:

Partition boards create microclimates; summer cooling (evaporative pads + fans) and winter heating (floor heating/hot air) maintain 18–25°C cage temperatures.

Lighting management:

LED strips simulate natural daylight cycles (16L:8D) to support ovarian development while avoiding overstimulation.

III. Proven Results: Data-Backed Improvements

A 10,000-hen farm trial demonstrated the following post-renovation benefits:

Egg production: Increased from 82% to 86%, with peak production extended by 2–3 weeks;

Mortality rate: Dropped from 8% to 5%, primarily due to fewer skeletal injuries and pecking deaths;

Egg quality: Breakage rate reduced from 3% to 0.8%, dirty egg rate from 2% to 0.5%;

Behavioral changes: Natural behaviors (perching, dust bathing) increased by 40%, while stress indicators (screaming, flapping) decreased by 60%.

Key Insight: When hens' physiological (e.g., comfortable temperatures, clean water) and behavioral (e.g., roosting, exploration) needs are partially met, stress levels decline, immunity strengthens, and productivity naturally improves.

IV. Future Directions: From Balance to Mutual Benefit

As consumer demand for animal welfare grows, cage designs are evolving toward "enriched stacked cages":

Modular systems: Flexible cage combinations to adjust density based on flock size;

Smart integration: Sensors monitor activity, body temperature, and feed intake for real-time health alerts;

Welfare certification compliance: Aligning with EU "enriched cage" standards or China’s Technical Specifications for Welfare Farming of Laying Hens to enhance market competitiveness.

Conclusion: High Density ≠ Low Welfare

The evolution of stacked cage design proves that high-density farming and animal welfare are not mutually exclusive. By scientifically optimizing cage structure, environmental control, and behavioral support, it is possible to achieve "efficient production" and "animal well-being" simultaneously. For farmers, this approach is not only ethical but also a strategic choice to boost egg production, reduce mortality, and strengthen market positioning.