Abstract
Increasing antimicrobial resistance has accelerated the exploration of phytobiotics as natural and sustainable feed additives to replace antibiotic growth promoters (AGPs) in poultry production. The antimicrobial, antioxidant, anti-inflammatory, and immunomodulatory effects of phytobiotics such as flavonoids, alkaloids, polyphenols, saponins, and essential oils from plants enhance the health and productivity of poultry. This review aimed to provide a comprehensive overview of the mechanisms and the beneficial effects of phytobiotics on antioxidant activity, immune responses, intestinal morphology, gut barrier integrity, gut microbiota modulation, and production performance in poultry. Phytobiotics enhance antioxidant defense through free radical scavenging activity and activation of endogenous antioxidant enzymes via the Nrf2 signaling pathway. Moreover, phytobiotics regulate cytokine expression, modulating immune responses, thereby increasing disease resistance and maintaining physiological homeostasis. Phytobiotics improve intestinal health by inhibiting pathogenic bacteria, promoting beneficial microbiota, increasing short-chain fatty acid production, and reinforcing tight junction proteins, leading to improved villous surface area and nutrient absorption efficiency. Studies have shown positive effects of phytobiotic inclusion on growth performance, egg production, intestinal health, and oxidative status in poultry. However, the efficacy of phytobiotics can be reduced during processing and storage as a result of thermal degradation, oxidation, and instability of bioactive compounds, which can reduce their antioxidant activity and biological functions in poultry. Nevertheless, phytobiotics remain promising as natural replacements for AGPs in enhancing poultry health, physiological status, intestinal function, and production performance in sustainable poultry production systems by modulating immune responses, improving antioxidant defense, maintaining intestinal morphology and gut barrier integrity, and promoting a balanced gut microbiota.