ISSUE FOCUS 28 FEED & ADDITIVE MAGAZINE July 2023 Stress in animals can be defined as any factor causing disruptions to their homeostasis, their stable internal balance. Stress engenders a biological response to regain equilibrium. High environmental temperatures are among the most important environmental stressors for poultry production, causing significant economic losses for the industry. CLIMATE CHANGE, THERMOREGULATION, AND STRESS Climate change has increased the prevalence and intensity of heat stress conditions in most poultry production areas all over the world. The optimum temperature for poultry animals’ well-being and performance –the so-called thermoneutral zone– is between 18 and 22°C. When birds are kept within this temperature range, they do not have to spend energy on maintaining constant body temperature. Heat stress is the result of unsuccessful thermoregulation in the animals, as they produce a higher quantity of heat than they can lose. It means that there is a negative balance between the net amount of heat produced by the animal and its capacity to dissipate this body heat to the environment. HEAT STRESS – CONTRIBUTING FACTORS This energy imbalance is influenced by environmental factors such as sunlight, thermal irradiation, air temperature, humidity, and stocking density, but also by animal-related factors such as body weight, feather coverage and distribution, hydration status, metabolic rate, and thermoregulatory mechanisms. Moreover, stressors can be additive and different factors such as feed quality and disease can convene leading to severe losses in health and performance. Increasing the respiratory rate -panting- is the main mechanism of chickens to loss heat, which is achieve by the evaporation of water from the respiratory tract however, relative humidity imposes a ceiling on water evaporation and subsequent dissipation of heat. Thus, the association of heat stress not only with high temperature, but also with high relative humidity. Heat stress can be classified into two main categories, acute and chronic: • Acute heat stress refers to a short and fast increase in environmental temperature (a few hours), in general, poultry animals show a degree of resilience to acute heat stress. • Chronic heat stress is when the high temWhat oxidative stress and inflammation have to do with it, why it affects gut health, and how in-feed products support mitigation strategies HEAT STRESS IN POULTRY Marisabel Caballero Global Technical Manager EW Nutrition
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