ISSUE FOCUS 46 FEED & ADDITIVE MAGAZINE June 2022 Heat stress causes substantial economic losses for broiler producers. In the USA, the average yearly losses associated with heat stress range from $128 to 165 million, and in China heat stress greatly contributes to the $2.7 billion in losses recorded in poultry livestock. Modern, fast-growing poultry genotypes exhibit higher metabolic activity, which increases heat production and makes broilers highly susceptible to heat stress. HEAT STRESS – AN INSIDIOUS THREAT Heat stress is triggered by a combination of high temperature and relative humidity levels, as both impact the ability of the birds to regulate body temperature through heat loss. Temperature and humidity data is often used to calculate the temperature humidity index (THI), which is a valuable measure to assess when birds are becoming heat-stressed (Figure 1). Heat stress’ harmful effects are myriad, from overall body weight decreases as feed intake drops, to falls in egg production rates and thinner eggshells due to reduced calcium uptake, to increases of up to 25% in feed conversion ratio. HEAT STRESS DISRUPTS HOMEOSTASIS These negative effects on poultry weight gain and feed conversion result from a complex cascade of physiological changes during increasing heat stress. In an effort to reduce body temperature and maintain thermoneutrality, the hypothalamic-pituitary-adrenal (HPA) axis of the neuroendocrine system aims to regulates body temperature via the production of T3 and T4 thyroid hormones. The initial functions of T3 and T4 hormones is to modulate protein synthesis for broiler growth; under heat stress these hormones are “mobilized” to regulate and balance body temperature. REDUCING HEAT STRESS IMPACT TO IMPROVE BROILERS’ PERFORMANCE ANDWELFARE Effective poultry heat stress management on the farm relies on a multifactorial approach to improve air flow and ventilation, spacing, dehumidification and evaporation, feeding strategies and nutritional management. To uplift the effects of these approaches, an efficient sustainable tool is adding quality yeast postbiotic in feed to protect birds’ against heat stress. Lin Wang Global Poultry Program Manager Phileo by Lesaffre Dr. Ruth Raspoet Poultry R&D Manager Phileo by Lesaffre
RkJQdWJsaXNoZXIy MTUxNjkxNQ==