Dr Raju Jakkula
MVSc, PhD (Animal Nutrition),
Nutrition & Health Solutions Manager, South Asia
Animal Nutrition & Health
DSM -Firmenich
With forecasts from the India Meteorological Department (IMD) and World Meteorological Organization (WMO) predicting another exceptionally hot year in 2025, poultry farmers must implement effective strategies to mitigate heat stress in commercial layers.
Heat stress, a condition where birds struggle to balance heat production and loss, is not just a welfare concern—it directly impacts egg production, egg quality, mortality, and profitability. In regions like India, where temperatures can climb to 48°C, proactive management is crucial.
Understanding Heat Stress and Its Impact on Layers
Heat stress occurs when environmental temperatures exceed a hen’s thermoneutral zone (18-25°C). Heat stress in layers causes panting, increased water consumption, lethargy, and wing spreading, and in severe cases, it may lead to open mouth breathing and death. Birds under heat stress divert energy from production to thermoregulation, triggering a cascade of negative effects:
- Reduced Feed Intake: Hens instinctively decrease feed consumption to minimize metabolic heat. This can lead to significant nutrient deficiencies. Research indicates that feed consumption can drop by 2.5-4g per degree Celsius above 30°C.
- Impaired Nutrient Absorption: Heat stress compromises gut integrity, reducing digestive enzyme activity and damaging the intestinal lining. This results in poor nutrient utilization and can increase susceptibility to disease.
- Disrupted Gut Microbiota: Heat stress can disrupt the balance of beneficial gut bacteria, leading to inflammation, reduced nutrient absorption, and immune system challenges.
- Lowered Egg Production & Quality: The combined effects of decreased feed intake, poor nutrient absorption, and physiological stress result in: A decline in egg production (losses ranging from 13% to 57% have been reported).
- Reduced egg weight (typically a 3% to 5% decrease).
- Thinner eggshells (shell thickness reductions of 1% to 10% are common).
- Decreased albumen quality, changes in yolk colour, and lower Haugh unit scores.
- An increased incidence of shell defects, cracks, and breakage.
- Increased Mortality: In severe cases, heat stress can lead to heatstroke and a sharp rise in mortality.
- Economic Impact: Heat stress in layers can severely impact profitability, with reduced egg production, increased eggshell breakage, and higher mortality leading to economic losses of ₹2 to ₹3 lakhs per month for a 10,000-bird farm. These challenges threaten both short-term revenue and long-term sustainability.
Strategic Interventions: A Multifaceted Approach
Combating heat stress requires a combined strategy focusing on environmental control and precision nutrition.
I. Optimizing the Layer Environment
Creating a cooler, more comfortable environment is paramount.
- Ventilation is Vital: Mechanical Ventilation: High-capacity fans are essential to maximize airflow, especially in high-humidity environments. Ensure proper fan placement and regular maintenance.
- Cross-Ventilation: Design and maintain houses to optimize cross-ventilation. Keep sidewall openings unobstructed to facilitate efficient air exchange.
- Cooling Strategies: Evaporative Cooling: ▪ Fogging Systems: Effective in lower humidity regions. Use appropriate droplet size to prevent excessive litter wetting.
- ▪ Evaporative Cooling Pads: When used with adequate ventilation, cooling pads can significantly reduce incoming air temperatures.
- ▪ Using thin gunny curtains with a drip system: The combination of shade and evaporative cooling lowers shed temperature by 3-5°C, improving bird comfort. Ensure proper installation, controlled drip rate, and drainage to avoid excess humidity.
- Roof Sprinklers: Periodic spraying can reduce heat absorption.
- Straw thatching of roof: Traditional, cost-effective method to reduce heat stress. It provides natural insulation, lowering shed temperatures and improving bird comfort. Ensure a thatch thickness of 6–8 inches, a proper slope for drainage.
- Reflective Roofing: Consider roofing materials with high reflectivity to minimize heat penetration.
- Insulation: Properly insulate roofs and sidewalls to minimize heat transfer into the poultry house.
- Stocking Density: Avoid overcrowding during hot periods to improve airflow and minimize bird-to-bird contact.
- Shade: Provide adequate shade outside the house to reduce radiant heat.
- Litter Management: Maintain dry litter to minimize ammonia production and improve air quality.
II. Precision Nutrition for Heat-Stressed Layers
Nutritional strategies are key to supporting layers during heat stress.
- Fine-Tuning Feed Formulation: Energy Balance: ▪ To reduce heat stress in layer birds during summer, partially replace carbohydrates with high-quality vegetable oils like soybean or rice bran oil at 1-2% of the diet. This approach increases dietary energy density, providing concentrated energy with less heat production than carbohydrates. It also improves feed palatability, enhances nutrient absorption, and helps maintain egg production under hot conditions.
- When temperatures exceed 27°C, consider increasing dietary energy by approximately 5%.
- Protein and Amino Acid Management: ▪ Maintain optimal crude protein levels, as reduced summer feed intake already lowers protein consumption.
- ▪ Ensure a balanced amino acid profile (lysine, methionine, threonine, etc.) by supplementing synthetic amino acids to support egg production and quality.
- ▪ Use highly digestible protein sources to minimize heat production from metabolism.
- ▪ Incorporate protease enzymes to enhance protein digestibility and nutrient absorption, helping to optimize performance in heat-stressed layers.
- Supplement the diet with 10-15% more vitamins and minerals to compensate for reduced intake and increased needs.
- Vitamin E: Supplement at 100-250 mg/kg to reduce oxidative stress and support immunity.
- Vitamin C: Supplement at 100-200 mg/kg to reduce stress response and support redox balance.
- Vitamin A: Supplement at 15000 IU/kg to support laying performance and immunity.
- 25-Hydroxyvitamin D₃ (Hy-D®): Supplement at 69 μg/kg feed to help layers manage heat stress effectively. Hy-D, a highly bioavailable form of Vitamin D₃, enhances calcium absorption, maintains eggshell quality even with reduced feed intake, and mitigates the negative effects of stress hormones. It supports immunity and helps sustain productivity during hot weather.
- Phosphorus: Increase phosphorus by 5% to compensate for increased urinary excretion.
- Zinc: Supplement at 80–120 mg/kg to boost immunity, reduce oxidative stress, and support eggshell quality.
- Osmo protectants: Include choline and betaine to support cellular hydration.
- Maintain a dietary electrolyte balance (DEB) of approximately 250 mEq/kg.
- Incorporate sodium from sodium bicarbonate (0.2 to 0.3%) to maintain acid-base balance.
- Use multi-component feed enzymes (Ronozyme MaxLay) to improve nutrient digestibility and maintain gut health.
- Consider multi strain poultry specific probiotics (PoultryStar®) to improve gut integrity and prevent performance losses.
- Feed Texture: Offer a coarse mash with added oil to improve palatability and stimulate feed intake. Avoid fine mash.
- Feed during cooler periods (early morning and late evening) to encourage intake and reduce metabolic heat.
- Implement “midnight feeding” with 1.5-2 hours of light to encourage feed intake during the coolest part of the night and support calcium deposition for eggshell formation.
- In very hot conditions, consider removing feed during the hottest part of the day.
- Provide supplemental calcium (e.g., coarse limestone) in the late afternoon to support eggshell formation.
- Availability: Ensure continuous access to cool, clean, and fresh water. Water-to-feed ratio increases from 1.6-2.0 (normal) to 3-4 under heat stress.
- Temperature: Maintain water temperature below 25°C by flushing water lines frequently, especially during peak heat periods (e.g., 10 AM – 4 PM).
- Supplementation: Consider adding electrolytes and Vitamin C to the drinking water.
- Optimizing Feeding Practices:
III. Additional Management Considerations
- Minimize Stress: Schedule activities like vaccinations and handling for cooler times of the day.
- Lighting Programs: Adjust lighting to encourage feeding during cooler periods.
- Monitoring: Closely monitor birds for signs of heat stress (panting, reduced activity, decreased egg production).
- Vaccination Timing: Administer vaccines early in the morning to minimize stress. Adjust medication volumes for increased water intake during water-based vaccination.
Conclusion
Effectively managing heat stress in commercial layers demands a comprehensive and proactive approach. By prioritizing environmental control, implementing precision nutritional strategies, and adhering to sound management practices, poultry producers can mitigate the negative impacts of heat stress, safeguard flock health, and optimize layer performance throughout the summer months. Consistent monitoring and timely adjustments remain essential for success.