Hydrolyzable tannins in local Thai plants: Potential applications as poultry feed supplements: A systematic review

The global shift toward antibiotic-free poultry production necessitates sustainable alternatives to conventional growth promoters. Hydrolyzable tannins (HTs) from plants have shown antimicrobial, antioxidant, and gut-modulatory effects, making them promising feed additives. However, reliance on imported tannins from temperate species limits access for tropical producers, especially in Thailand. This study aimed to systematically evaluate locally available Thai plant species as alternative sources of HTs for poultry feed, with a focus on their biological activities, economic feasibility, and practical integration potential.

A systematic literature search (2020-2024) was conducted using PubMed, ScienceDirect, and the Thai citation index. Studies assessing Thai plant-derived HTs and their antimicrobial, antioxidant, and gut health effects were included in the study. A total of 21 studies covering 24 plant species were analyzed. Data extraction included tannin type, target microbes, experimental outcomes, and yield/economic feasibility, assessed through a validated scoring system.

Gallic and ellagic acids were the predominant bioactive compounds reported. HT-rich extracts demonstrated strong antimicrobial effects against 19 pathogenic bacterial species and enhanced the growth of beneficial gut microbiota, including Lactobacillus spp. and Faecalibacterium prausnitzii. Manihot esculenta (cassava) and Senna siamea (Siamese cassia) emerged as top candidates based on both bioactivity and economic feasibility. In vivo studies, although limited, supported their positive impact on gut health in broilers.

Thai HT-rich plants, particularly cassava and Siamese cassia, show strong potential as sustainable feed additives in poultry production. These species offer dual benefits: antimicrobial and gut-modulatory effects and reduced reliance on expensive imported tannins. However, more standardized extraction protocols and large-scale in vivo trials are essential to validate efficacy, optimize dosage, and ensure feed safety.