Herbs impact on poultry health and antimicrobial resistance: a scoping review with one health perspective.

Background: According to evidence, medicinal plants such as thyme, rosemary, and fenugreek were beneficial for human health. Recently, these plants showed a great impact in animal health, particularly in poultry.

Objectives: To map the body of literature on the impact of medicinal plants on poultry health, including growth performance, gut microbiota, and mortality.

Eligibility criteria: Articles published in the English language from January 2019 to February 2023 randomized controlled trials, quasi-experimental studies, conducted on hens, chickens, or chicks that aimed to assess the effect of medicinal plants with or without prebiotics, on health-related outcomes including growth performance, mortality rate, and gut microbiota composition.

Sources of evidence: From December 2022 to February 2023, a systematic search on PubMed, Science Direct, and Google Scholar was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Extension for Scoping Reviews guidelines.

Charting methods: Data charting was performed using a standardized form on Excel 365 that included study identification features, population and sample size, study groups, intervention description, follow-up period, and main outcomes.

Results: After the second screening, 38 articles were included. Results showed that thyme, rosemary, and peppermint were widely tested, and they were effective in promoting body weight gain, feed conversion ratio, live body weight, and microbiota, and in reducing mortality rate and intestinal multiple resistant bacteria. Cinnamon, lemon, garlic, and fenugreek were less commonly experimented. However, some studies that they were effective in improving growth performance and improving gut microbiota in healthy chickens.

Conclusions: Various studies confirmed that 5 to 6 g/kg of thyme powder was effective in improving growth performance and gut microbiota in healthy chickens. Further experiments are needed to compare the impact of thyme to antibiotics in chickens infected with multiple drug-resistant bacteria.