Introduction
Heat stress is a significant environmental stressor that affects poultry productivity, health, and welfare, particularly in tropical and subtropical regions. When ambient temperatures rise above the thermoneutral zone (approximately 21–25°C for poultry), birds experience heat stress, resulting in reduced feed intake, poor growth performance, compromised immunity, and increased mortality. Nutritional strategies play a vital role in mitigating the negative impacts of heat stress.
Nutritional Management Strategies
1. Energy and Protein Adjustments
- Energy Density: Birds reduce feed intake under heat stress, so diets should be more energy-dense (e.g., increased dietary fat) to maintain energy intake.
- Fat Supplementation: Adding oils (e.g., soybean, palm, or animal fat) reduces heat increment compared to carbohydrates and improves energy efficiency.
- Protein Balance: Lower total protein but optimize essential amino acid balance (e.g., methionine, lysine, threonine) to reduce nitrogen excretion and metabolic heat.
2. Electrolyte Balance
- Electrolyte balance (Na⁺, K⁺, Cl⁻) helps maintain acid–base status.
- Supplementation: Add sodium bicarbonate, potassium chloride, and ammonium chloride to correct acid–base imbalance.
- Optimal dietary electrolyte balance (DEB) is 250–300 mEq/kg of diet.
3. Antioxidants and Vitamins
- Vitamin C: Reduces oxidative stress and improves thermotolerance (500–1000 mg/kg diet or via drinking water).
- Vitamin E: Works synergistically with Vitamin C; protects cell membranes (100–250 mg/kg).
- Selenium: Essential for glutathione peroxidase activity; supports antioxidant defense (0.3 ppm, organic Se preferred).
- Betaine: Acts as an osmolyte and methyl donor; helps maintain water balance and supports energy metabolism.
4. Minerals
- Zinc and Chromium: Improve antioxidant status and stress resistance.
- Organic minerals have better absorption and efficacy under stress.
- Magnesium: Has a calming effect and improves tolerance to stress.
5. Feed Additives
- Probiotics and Prebiotics: Improve gut health and immunity.
- Phytogenics: Plant extracts (e.g., ginger, turmeric, oregano) reduce inflammation and improve thermotolerance.
- Enzymes: Help digest feed efficiently, minimizing fermentation and heat production.
6. Water Management
- Ensure cool, clean water is available at all times.
- Supplementation with electrolytes, vitamins, or organic acids in water is effective during peak heat hours.
7. Feeding Practices
- Feeding Times: Offer feed during cooler parts of the day (early morning, late evening).
- Wet Feeding: Can help increase feed intake and reduce internal body temperature.
Practical Formulation Tips
- Increase dietary fat to 4–6% during hot weather.
- Use protected or encapsulated vitamins to prevent degradation.
- Use pelleted or crumbled feed to reduce feed wastage and energy expenditure.
- Monitor body weight, feed conversion ratio (FCR), and mortality to evaluate success.
Conclusion
Nutritional management is a cost-effective and practical approach to mitigate the adverse effects of heat stress in poultry. By adjusting energy, protein, electrolyte balance, and incorporating antioxidants and additives, poultry producers can maintain bird health, productivity, and profitability even under extreme heat conditions.