the role of medicinal plants in poultry production: a systematic analysis of their efficacy as antibiotic alternatives for enhancing health, growth, and controlling disease

The global poultry industry, a cornerstone of food security, faces immense pressure to mitigate its reliance on antibiotic growth promoters (agps) due to the escalating crisis of antimicrobial resistance (amr). this has catalyzed an urgent search for sustainable, effective, and natural alternatives. medicinal plants, with their rich repertoire of bioactive compounds such as phenolics, flavonoids, terpenoids, and alkaloids, present a profoundly promising solution. these phytogenics exhibit a wide spectrum of biological activities, including antimicrobial, antioxidant, anti-inflammatory, and immunomodulatory properties. this systematic review synthesizes a global body of evidence, integrating significant findings from international and iranian research, to critically evaluate the multifaceted effects of various medicinal plants on poultry health, growth performance, and disease resistance. the consolidated findings robustly demonstrate that dietary supplementation with extracts or powders from plants like oregano (origanum vulgare), thyme (thymus vulgaris), garlic (allium sativum), black seed (nigella sativa), and many others can significantly enhance growth parameters (body weight gain, feed conversion ratio), improve gut morphology and microbiota, potentiate humoral and cellular immune responses, and confer substantial protection against bacterial (clostridium perfringens, escherichia coli, salmonella spp.), viral (newcastle disease, avian influenza), and parasitic (eimeria spp.) challenges. the mechanisms are pleiotropic, involving direct pathogen inhibition, enhancement of digestive enzyme secretion, reduction of oxidative stress, and modulation of immune gene expression. this review concludes that phytogenic feed additives are viable, natural, and effective alternatives to in-feed antibiotics, aligning with the one health paradigm. however, challenges regarding the standardization of active compounds, optimal dosage determination, and large-scale application efficacy must be addressed through future research for their full integration into sustainable poultry production systems.