Summer Management in Poultry: Combatting Heat Stress

Understanding THI: A Key Indicator in Managing Poultry Heat Stress

The thermoneutral zone refers to that temperature range where the bird is in a state of physiological comfort and there is a balance of energy resources. The normal thermoneutral zone for poultry falls between 15°C and 24°C. The Temperature Humidity Index (THI) is an important indicator for the thermoneutral zone.

The Temperature-Humidity Index (THI) is a combined measure of air temperature and humidity, providing an indication of heat stress experienced by animals, including poultry. High THI values indicate greater heat stress, which can adversely affect poultry health and productivity.

Poultry primarily dissipate heat through respiration and limited evaporative cooling. Higher THI for longer periods leads to panting in poultry, which however may be insufficient to effectively control the body temperature of the birds.

High humidity levels impede this process, as the air is already saturated with moisture, making it difficult for the birds to lose heat through evaporation. Elevated humidity combined with high temperatures increases the THI, thereby heightening heat stress in poultry.

Physiological changes in poultry due to heat stress:

• Oxidative stress: Heat stress causes an imbalance between the production of free radicals and the ability of the body to detoxify their harmful effects through neutralization by antioxidants. This oxidative stress damages cells, proteins, and DNA, leading to impaired cellular functions and increased susceptibility to diseases. In poultry, this can result in weakened immune responses and higher mortality rates.
• Acid base imbalance: Heat stress disrupts the normal acid-base balance in poultry by altering the pH levels in their blood and tissues. This imbalance can lead to metabolic acidosis or alkalosis, impairing metabolic processes and enzyme activities. It affects the bird's overall health, leading to decreased productivity and increased vulnerability to infections. 

• Respiratory alkalosis: During heat stress, poultry increase their respiration rate (panting) to dissipate excess body heat, leading to excessive loss of carbon dioxide. This causes respiratory alkalosis, a condition where the blood pH becomes too alkaline. It can result in muscle tremors, weakness, and reduced oxygen delivery to tissues, further stressing the birds.

Behavioural changes:

• Decreased feed intake: Poultry reduce their feed consumption in response to high temperatures as eating generates additional body heat. Reduced feed intake leads to inadequate nutrient absorption, affecting growth, egg production, and overall health. It can also result in weight loss and poor body condition. 

• Increased water intake: To counteract the effects of heat stress, poultry increase their water consumption to cool down their bodies. While increased hydration is beneficial, it can also lead to diluted electrolyte levels, causing imbalances that affect bodily functions. This behaviour indicates that birds are under thermal stress and struggling to maintain homeostasis. 

• Less walking: Heat-stressed birds tend to reduce their physical activity to conserve energy and minimize heat production. However, reduced movement can lead to poor circulation, decreased muscle tone, and increased risk of developing leg problems or sores from prolonged sitting. 

• Elevated wings: Birds lift their wings away from their bodies to increase air circulation and dissipate heat. This behaviour indicates severe discomfort and stress. While it helps cool the birds, it also exposes them to potential injuries and skin issues due to increased exposure.

Production changes:

• Poor FCR: FCR is the efficiency with which birds convert feed into body mass. Heat stress reduces this efficiency. Poor FCR means that more feed is required to achieve the same weight gain, increasing production costs and reducing profitability for poultry farmers. 

• Reduced body weight: Due to decreased feed intake and poor nutrient absorption, heat-stressed birds often experience stunted growth and weight loss. Lower body weight affects market value and profitability. It also indicates that the birds are not thriving, which can lead to higher mortality rates and economic losses. 

• Reduced meat and egg quality: Heat stress negatively impacts the quality of meat and eggs produced by poultry. In broilers, this can result in meat with poor texture and higher fat content. In layers, egg production may decrease, and the eggs themselves may have thinner shells and lower internal quality. These changes reduce the marketability and consumer acceptance of poultry products.

Management Strategies to Keep Your Poultry Cool and Comfortable

To mitigate the harmful effects of heat stress, it's crucial to implement effective management strategies tailored to the specific needs of your poultry. Here are some strategies poultry farmers can apply to keep their broiler and layer flocks cool:

Water Management:

• Provide clean, cool water: Ensure that water is readily available and kept at a cool temperature to encourage drinking. Use sanitizers to maintain water quality and prevent the spread of diseases.
• Increase waterers: During extreme heat, increase the number of water points by 25-30% to ensure all birds have easy access.
• Shade and insulation for water tanks: Cover water tanks with insulating materials such as wet gunny bags to prevent water from heating up.

Housing Management:

• Energy-Efficient Insulation: Ensuring poultry houses (including roof) are well-insulated with energy-efficient materials to keep the environment cool. Installation of a white coloured roof also helps mitigate the temperature inside the shed.
• Shading Structures: If birds have access to outdoor areas, construct shading structures over outdoor areas to protect birds from direct sunlight.
• Ventilation: Ensure adequate ventilation by providing ridge ventilation and installing fans to circulate air and remove hot air from the shed.
• Misting systems: Install sprinklers or mis-fans to cool the shed. These systems can lower the ambient temperature by up to 5-10 degrees, depending on the quality and setup.

General Management:

• Litter management: Maintain fresh litter of 5 cm thickness and rake or stir it 2-3 times a day during cooler hours to prevent heat build-up.
• Avoid overcrowding: Ensure birds have enough space to reduce stress and allow for better air circulation.
• Timing of stressful activities: Schedule activities like shifting, transportation, de-beaking, and vaccination during cooler parts of the day to minimize heat stress.
• Regular Monitoring: Regularly monitoring the health and behaviour of birds to detect early signs of heat stress and take corrective actions promptly.

Feed Management:

• Feeding schedule: Offer feed during the early morning and late evening when temperatures are cooler to encourage eating.
• Nutritional supplements: Add extra 20-30% vitamins and trace minerals to the feed. Specifically, supplement with Vitamin C, E, B2, B6, B12, ammonium chloride, potassium chloride, and sodium bicarbonate to support the birds' health during heat stress.
• Herbal supplements: Use herbs like Ocimum sanctum, Withania somnifera, and Emblica officinalis, which have been shown to reduce heat stress by several studies.

Swap Synthetic Vitamins to Natural Ones

During the summer, heat stress increases the chickens' need for Vitamin C as they are unable to synthesize sufficient amounts to meet heightened physiological demands. Vitamin C plays a crucial role in amino acid and mineral metabolism and the synthesis of certain hormones. It also helps mitigate the adverse effects of heat stress by reducing oxidative stress and supporting immune function, thus its supplementation is crucial during summer.

In addition to Vitamin C, Vitamin E is also essential for poultry during summer. Vitamin E acts as a powerful antioxidant, protecting cells from oxidative damage caused by heat stress. It also plays a role in immune function and helps maintain the integrity of tissues, which is critical in managing the stress of high temperatures.

Why choose natural vitamins?

Natural vitamins are generally better than synthetic ones due to their higher bioavailability and the presence of co-factors that enhance their effectiveness. Natural vitamins are derived from whole food sources and contain a complex of nutrients that work synergistically within the body. This holistic approach ensures that the vitamins are absorbed and utilized more efficiently compared to synthetic vitamins, which are often isolated compounds.

Synthetic vitamins, on the other hand, may lack the necessary co-factors for optimal absorption and can sometimes be harder on the digestive system. Therefore, incorporating natural sources of vitamins into poultry diets can provide more comprehensive health benefits, especially during the challenging summer months.

Apply Anti-Stress Herbal Solutions

The use of polyherbal formulations containing natural Vitamin E, Vitamin C, bio-flavonoids and herbal extracts having antioxidant and anti-stress properties can help poultry effectively counter heat stress according to several studies.

Herbs like Phyllanthus emblica, Withania somnifera, and Ocimum sanctum present in some of these formulations (such as STRESROAK oral liquid, AYUCEE liquid or AYUVIT-E) possess antiviral, immunomodulatory, and anti-lipid peroxidation properties, enhancing the birds' ability to cope with heat stress and maintain productivity.

Implementing these strategies will help mitigate the adverse effects of heat stress, ensuring your broiler and layer flock remain healthy and productive throughout the summer months too!