Heat Stress in Poultry: Physiological Impacts and the Role of Nutraceutical Interventions—A Narrative Review

Heat stress (HS) is a major constraint to poultry productivity, especially in regions experiencing high environmental temperatures. It disrupts thermoregulation, reduces feed intake and impairs growth, egg production, reproductive performance, intestinal integrity and immune function. Plant‐based nutraceuticals have therefore attracted interest as complementary interventions for improving poultry resilience to thermal stress. This narrative review was designed to synthesise evidence on the physiological effects of HS and the potential of phytogenic nutraceuticals to alleviate heat‐induced dysfunction in poultry. The narrative review was created by identifying relevant literature through targeted searches of Google Scholar, Scopus and Web of Science using terms related to heat exposure, poultry species, nutraceutical interventions and physiological or productive responses. Reference lists were also examined to identify additional studies. No strict publication‐year restriction was applied, and peer‐reviewed empirical and review articles relevant to the objectives were considered. The reviewed evidence suggests that bioactive compounds from botanical sources such as Moringa oleifera , Curcuma longa , Zingiber officinale and Lippia species may strengthen antioxidant defences, regulate endocrine and immune responses, protect intestinal integrity and support productive and reproductive performance under HS. However, their effectiveness varies with plant source, phytochemical composition, active‐compound concentration, inclusion level, bioavailability, poultry type and heat‐exposure conditions. Wider application is constrained by inconsistent product composition, limited dose–response information, uncertainties regarding long‐term safety and insufficient validation under commercial production conditions. Future research should standardise phytochemical characterisation, extraction and processing methods, evaluate bioavailability and apply transcriptomics, metabolomics and microbiome analyses to clarify mechanisms of action. These advances could support the scientific validation of indigenous plants and their development into accessible, region‐specific nutraceutical interventions for climate‐smart poultry production.