Appropriate methods to address the challenges of heat stress can be highly variable and are dependent upon the production environment at hand. Effectively identifying and preventing heat stress in poultry is critical to protecting the well-being of flocks and ensuring optimal poultry yield.
Senior Director Technical Services
Elanco
The effects of heat stress caused by high temperatures is a concern for poultry producers globally and is the cause of significant economic losses for the industry. The U.S. livestock production industry suffers an annual loss of $1.69 to $2.36 billion because of high environmental temperature, with the poultry industry tracking an estimated annual loss between $128 and $165 million.1 Modern poultry are particularly susceptible to heat and humidity, largely because they lack effective mechanisms to regulate body temperature.2
Appropriate methods to address the challenges of heat stress can be highly variable and are dependent upon the production environment at hand. Effectively identifying and preventing heat stress in poultry is critical to protecting the well-being of flocks and ensuring optimal poultry yield.
SYMPTOMS AND EFFECTS OF HEAT STRESS IN POULTRY
Heat stress presents itself in poultry in several ways, including increased water consumption, reduced feed intake and decreased physical activity. Birds suffering from heat stress also exhibit some behavioral signs, such as spreading their wings to cool their bodies, squatting low to the ground and resting frequently.3
Heat stress impacts the bird’s metabolic processes, which leads to decreased nutrient absorption, compromising growth and performance. Under heat stress conditions, birds prioritize dissipating heat over eating which leads to reduced feed intake and associated reduction in daily nutrient intake.
While lower feed intake and calorie absorption minimize heat produced by poultry’s rapid metabolic processes, it ultimately impairs the digestibility of nutrients and overall digestive function.4 These factors can compromise growth and weaken the immune system, making birds susceptible to enteric diseases.
If not effectively managed, heat stress in poultry can lead to more severe consequences. Possible outcomes of unmitigated heat stress include hypoperfusion, respiratory distress, and organ failure. Birds with existing respiratory and cardiovascular problems are particularly vulnerable to the adverse effects of heat stress. More importantly, the profound behavioral and physiological changes poultry experience under heat stress can increase mortality, resulting in economic losses for producers.
ROLE OF NUTRITION IN COMBATTING HEAT STRESS
Nutrition is integral in combatting heat stress in poultry. Advanced nutrition can support birds’ physiological responses to high temperatures, improving their thermotolerance. Management of nutrient balance in poultry is possible by providing formulated diets with high energy density and improved nutrient digestibility that meet their rapid metabolic processes.
The texture of feed can also play a role in combating heat stress. Pellets and crumbles typically have less dust compared to mash feed. Dust can exacerbate respiratory issues in poultry, which can be problematic under heat stress conditions, however, pellets and crumbles often contain a balanced mix of nutrients, which can improve digestibility and nutrient absorption. Alternatively, mash feed requires more water to consume compared with pellets and crumbles. During hot weather, consuming mash feed can help contribute to birds’ overall water intake, helping them to stay hydrated.
To further elevate immune function and enhance gut health, producers can consider feed additives such as probiotics, prebiotics and yeast-based products. Other considerations for feed additives include synthetic amino acids and enzymes, which are effective for feed digestibility. Producers should favor quality fat over carbohydrates as a primary energy source in poultry feed. Medical additives, such as coccidiostats, can further prevent infectious diseases but should be incorporated appropriately for flocks.
As mentioned, poultry experience increased respiratory rates when exposed to high temperatures. Panting results in electrolyte imbalances, but sodium, potassium, and chloride supplements will regulate hydration levels. Access to clean water is also essential in reducing the likelihood of developing symptoms of heat stress. The benefits of these additives support birds’ overall health by improving nutrient absorption and reducing inflammation, both of which are vital to alleviating heat stress.
OTHER CONSIDERATIONS TO MANAGE THE EFFECTS OF HEAT STRESS
Poultry can be susceptible to heat stress year-round, especially in modern housing. Ventilation systems are effective in poultry housing to increase air circulation, reduce air temperature and humidity, and decrease the potential for birds to experience heat stress. Exhaust fans and structural venting push hot air out and maintain air quality. Evaporative cooling systems such as foggers, misters, and cool cell pads are also effective for heat management. However, it is best practice to use cooling devices in combination with ventilation methods to avoid an increase in humidity.
Additional strategies include:
• Shading structures to minimize heat buildup and create a cool and comfortable environment
• Controlled management of litter moisture content to prevent it from becoming excessively hot
• Lowering the population of birds in the house to improve air circulation, lessen competition for feed, and reduce environmental stress on birds
• Adjusting feed schedules so birds eat when temperatures are cooler to encourage better food intake
Readiness to combat heat stress among producers is vital for protecting flocks during warmer months and year-round. Skillful identification of heat stress symptoms safeguards the health and safety of flocks, and targeted strategies such as nutritional supplements, coccidiostats, adequate ventilation, and access to clean water are effective preventative measures to improve the comfort of birds’ environment and ensure productivity.
Sources:
1. St-Pierre NR, Cobanov B, Schnitkey G. Economic losses from heat stress by US livestock industries. J Dairy Sci. (2003) 86:52–77. 10.3168/jds.S0022-0302(03)74040-5
2. Fraley, GS. “Heat stress and poultry production: a comprehensive review.” NCBI, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10591017/. Accessed 5 May 2024
3. Lara, L. J., & Rostagno, M. H. (2013). Impact of Heat Stress on Poultry Production. Animals, 3(2), 356-369. https://doi.org/10.3390/ani3020356
4. Onagbesan, O. M., Uyanga, V. A., Oso, O., Tona, K., & Oke, O. E. (2023). Alleviating heat stress effects in poultry: Updates on methods and mechanisms of actions. Frontiers in Veterinary Science, 10. https://doi.org/10.3389/fvets.2023.1255520
About Alastair Thomas
Alastair Thomas, Ph.D., is a Senior Director of U.S. Poultry Technical Services and Nutritional Health at Elanco. Thomas provides specialized feed additive and microbiology technical support to the poultry technical and marketing team for animal health product groups and services.
