Nutritional Adaptations to Enhance Poultry Resilience Against Heat Stress
Dr. Sonali Namdeo
Assisstant Professor, Arawali veterinary college, Sikar
Abstract
Heat stress is a critical challenge in poultry production, occurring when ambient temperatures exceed the birds’ thermoneutral zone (16°–25°C). It disrupts physiological functions, leading to reduced feed intake, impaired metabolism, and compromised thermoregulation. These effects result in decreased body weight gain, lower egg production, weakened immune function, and increased mortality. Heat stress also damages intestinal integrity, alters gut microbiota, and induces oxidative stress, further affecting poultry health and productivity. Nutritional strategies play a crucial role in mitigating these adverse effects. Antioxidants such as vitamin E, vitamin C, selenium, lycopene, curcumin, resveratrol, and epigallocatechin gallate enhance oxidative defence mechanisms. Electrolyte supplementation with potassium chloride, sodium bicarbonate, zinc, and magnesium help maintain acid-base balance. Additionally, probiotics, prebiotics, and phytobiotics improve gut health and immune function. Dietary manipulations, including feed form modifications, optimized feeding schedules, and cold-water supplementation, further aid in alleviating heat stress. A combination of these nutritional strategies, along with effective management practices, is essential to enhance poultry resilience against heat stress and sustain productivity in hot climates.
Keywords: Heat stress, nutrition, poultry, prebiotic, probiotic,
Introduction
Heat stress occurs when an animal or bird is unable to dissipate excess body heat effectively due to high ambient temperature, humidity, and metabolic heat production. This leads to physiological and biochemical imbalances, negatively affecting growth, reproduction, immunity, and overall productivity. Heat stress in poultry occurs when the ambient temperature exceeds the birds’ thermoneutral zone (16°–25°C), surpassing their ability to dissipate excess body heat. Poultry, especially broilers and layers, lack sweat glands and primarily rely on panting, increased water intake, and reduced activity to regulate body temperature. However, prolonged exposure to high temperatures leads to physiological, metabolic, and behavioural disturbances, negatively impacting growth, reproduction, and overall health (Habashy et al., 2017).
Causes of Heat Stress in Poultry:
- High Ambient Temperature– Sudden or prolonged exposure to hot climates
- High Humidity– Reduces evaporative cooling efficiency
- Poor Ventilation– Limits heat dissipation
- Overcrowding – Increases body heat accumulation
- Inadequate Water Supply– Prevents proper thermoregulation
- Impact of Heat Stress on Poultry
Heat stress occurs when the ambient temperature exceeds the thermoneutral zone of poultry (16°–25°C) and surpasses their ability to dissipate excess heat. This leads to physiological and metabolic disturbances, ultimately reducing productivity and profitability in the poultry industry (Onagbesan et al., 2023).
A. Physiological and behavioural Effects
- Increased respiratory rate and panting→ Leads to respiratory alkalosis, disrupting acid-base balance
- Reduced feed intake (FI)→ Causes nutrient deficiency, leading to weight loss and poor growth.
- Altered metabolism→ Increased breakdown of muscle proteins and fats to compensate for energy loss
- Impaired thermoregulation→ Results in dehydration, electrolyte imbalance, and oxidative stress
B. Effect on Growth Performance and Productivity
Heat stress significantly impairs poultry performance by:
- Reducing body weight gain (BWG) and feed conversion efficiency
- Lowering egg production, shell quality, and hatchability in laying hens
- Increasing mortality and morbidity due to immune suppression
- Compromising meat quality (pale, soft, and exudative meat) due to muscle damage
C. Effect on Intestinal Integrity and Gut Microbiota
- Heat stress damages the intestinal mucosal barrier, leading to increased permeability
- Reduces the population of beneficial gut bacteria (Lactobacillus, Bifidobacterium) while increasing harmful bacteria (Clostridium, coli)
- Alters nutrient absorption due to changes in gut morphology (reduced villus height and crypt depth)
Fig. Dietary Interventions and Their Benefits in Alleviating Heat Stress in Poultry
(Source: Onagbesan et al., 2023)
D. Effect on Oxidative Stress and Immune System
- Heat stress triggers oxidative stress, leading to excessive reactive oxygen species (ROS) production
- Oxidative damage results in cell apoptosis, lipid peroxidation, and protein oxidation
- The immune system is weakened, making birds more susceptible to infections and inflammatory disorders
- Nutritional Strategies to Combat Heat Stress in Poultry
To counteract heat stress, various nutritional interventions have been explored, including antioxidants, electrolytes, feed additives, and dietary modifications (Abdel-Moneim et al., 2021).
A. Antioxidants and Vitamins
Antioxidants play a crucial role in neutralizing ROS and maintaining cellular integrity.
a. Vitamin E (α-Tocopherol)
- Fat-soluble antioxidant that protects cell membranes from lipid peroxidation
- Enhances immune function by increasing antibody production and lymphocyte proliferation
- Supplementation (100–250 mg/kg) improves feed conversion ratio and egg production in heat-stressed layers
b.Vitamin C (Ascorbic Acid)
- Water-soluble antioxidant that reduces stress-induced corticosterone levels
- Enhances calcium metabolism, improving eggshell formation in layers
- Supplementation (200–400 mg/kg) improves weight gain, egg production, and immune response
c. Selenium (Se)
- Essential trace mineral involved in glutathione peroxidase (GSH-Px) activity.
- Protects against oxidative stress-induced muscle damage and improves meat quality.
- Selenium nanoparticles (0.3 mg/kg) enhance feed conversion efficiency and immune response.
d. Lycopene
- A carotenoid found in tomatoes that reduces oxidative stress and improves antioxidant enzyme activity
- Supplementation (200–400 mg/kg) enhances growth, feed intake, and meat quality in heat-stressed broilers
e. Curcumin (Turmeric)
- Potent polyphenol with anti-inflammatory and antioxidant properties
- Enhances heat shock protein (HSP) expression, reducing cellular damage
- Supplementation (100–200 mg/kg) improves weight gain, immune function, and antioxidant activity
f. Resveratrol
- A polyphenol that enhances immune function and gut integrity
- Reduces the overexpression of HSP27, HSP70, and HSP90, which are markers of cellular stress
- Supplementation (300–500 mg/kg) improves feed intake, body weight, and egg production
g. Epigallocatechin Gallate (EGCG)
- A major catechin in green tea with strong antioxidant properties
- Enhances glutathione peroxidase, superoxide dismutase, and catalase activity
- Supplementation (300–600 mg/kg) improves growth performance and reduces oxidative damage
- B. Electrolyte and Mineral Supplementation
Heat stress increases respiratory alkalosis, leading to electrolyte imbalances. Supplementing electrolytes helps maintain acid-base homeostasis.
a. Potassium Chloride (KCl)
- Essential for maintaining osmotic balance and thermoregulation
- Supplementation (0.5% in drinking water) improves feed intake and growth
b. Sodium Bicarbonate (NaHCO₃)
- Helps counteract respiratory alkalosis caused by panting
- Enhances eggshell quality by improving calcium absorption and carbonate availability
c. Zinc (Zn) and Magnesium (Mg)
- Involved in enzyme activation, protein synthesis, and antioxidant defence
- Zinc methionine (25–100 mg/kg) improves feed conversion, immune response, and meat quality
C. Probiotics, Prebiotics, and Phytobiotics
Gut health plays a crucial role in nutrient absorption, immune function, and stress resistance.
a. Probiotics (Beneficial Bacteria)
- Lactobacillus, Bacillus subtilis, and Enterococcus faecium improve gut microbiota balance
- Enhances immune response and nutrient digestibility
- Probiotic supplementation (250–500 ppm) improves egg production and intestinal health
b. Prebiotics (Nutrient Sources for Gut Bacteria)
- Mannan-oligosaccharides (MOS) and galacto-oligosaccharides (GOS) improve gut microbiota composition
- Enhance calcium absorption and eggshell formation
- Prebiotic supplementation (1–2.5% of diet) improves intestinal barrier function
c. Phytobiotics (Plant-Derived Compounds)
- Include essential oils (oregano, thyme, garlic), flavonoids, and alkaloids
- Have antimicrobial, antioxidant, and immune-modulating effects
- Supplementation enhances gut health and reduces oxidative stress
D. Additional Dietary Manipulations
a. Feed Form and Timing
- Pelleted feed is preferred over mash feed for better digestibility
- Feeding during cooler parts of the day (early morning and evening) improves intake
b. Fat and Protein Adjustments
- Increasing dietary fat (5–7%) provides an alternative energy source with lower heat production
- Adjusting protein levels reduces excess metabolic heat generation
c. Cold Drinking Water
- Reduces body temperature and improves feed intake
- Electrolyte-enriched water enhances hydration and thermoregulation
- Recommendations for Poultry Industry
- Integrate nutritionaland management strategies (cooling, ventilation) to combat heat stress.
- Adopt precision feedingtechniques to optimize nutrient intake.
- Conduct further researchto refine feeding strategies for different poultry species and climates.
Conclusion
Heat stress poses a significant challenge to poultry production, negatively affecting growth, productivity, immune function, and overall health. It disrupts metabolic processes, damages intestinal integrity, and induces oxidative stress, leading to economic losses in the poultry industry. Implementing effective nutritional strategies, including antioxidants, electrolytes, probiotics, prebiotics, and phytobiotics, can help mitigate these adverse effects. Additionally, dietary modifications such as feed form adjustments, strategic feeding schedules, and cold-water supplementation further enhance poultry resilience to heat stress. A holistic approach integrating nutritional interventions with proper management practices, such as ventilation and cooling systems, is essential for optimizing poultry performance under heat stress conditions. Continued research and precision feeding strategies will further improve poultry adaptation to heat stress, ensuring sustainable and profitable production in challenging climatic conditions.
References
Onagbesan, O. M., Uyanga, V. A., Oso, O., Tona, K., and Oke, O. E. (2023). Alleviating heat stress effects in poultry: updates on methods and mechanisms of actions. Frontiers in Veterinary Science. 10: 52-55.
Abdel-Moneim, A. M. E., Shehata, A. M., Khidr, R. E., Paswan, V. K., Ibrahim, N. S., El-Ghoul, A. A., and Ebeid, T. A. (2021). Nutritional manipulation to combat heat stress in poultry–A comprehensive review. Journal of Thermal Biology. 98: 25-29.
Habashy, W.S., Milfort, M.C., Rekaya, R., Aggrey, S.E. (2019). Cellular antioxidant enzyme activity and biomarkers for oxidative stress are affected by heat stress. Int. J. Biometeorol. 63: 1569–1584.
