Alpinia katsumadai and Wurfbainia vera Extracts Modulate Antioxidant Function and Intestinal Morphology in Danzhou Chickens via Gut Microbiota–Metabolite Interactions Involving Hydroxyoctadecadienoic Acid Metabolism and Bacteroidota Remodeling

This study evaluated the effects of supplementing Alpinia katsumadai and Wurfbainia vera extracts on the growth performance, antioxidant capacity, intestinal metabolites, and microbiota of Danzhou chickens. Using Danzhou broilers, we examined the individual or combined inclusion of Alpinia katsumadai and Wurfbainia vera extracts in a 2 × 2 factorial layout. Four hundred and eighty female dual-purpose chickens were randomly assigned to four treatments (six replicates of 20 chicks each): control basal diet (CON), basal + 600 mg kg−1Alpinia katsumadai (T1), basal + 600 mg kg−1 Wurfbainia vera (T2), or basal + 600 mg kg−1 Alpinia katsumadai + 600 mg kg−1 Wurfbainia vera (T3). All treatments differed significantly from CON. For intestinal morphology, T1, T2, and T3 increased jejunal villus height and villus-to-crypt ratio while reducing crypt depth. T1 exceeded CON (p < 0.05), and an interaction was detected. T1 raised the abundances of Bacteroidota, Bifidobacterium, Tidjanibacter, and Phocaeicola relative to CON (p < 0.05). T3 exhibited higher activities of glutathione peroxidase and catalase than CON, T2, and T1 (p < 0.05). Metabolomically, T1, T2, and T3 elevated intestinal Menaquinone-9, lecithin, and L-galactono-1,5-lactone versus CON (p < 0.05). T3 lowered 3-(R)-Hydroxyoctadecadienoic acid and 9-(R)-Hydroxyoctadecadienoic acid versus CON and T1, and increased eugenol versus CON (p < 0.05). Overall, T1 and T2, especially in combination, enhance antioxidant capacity, improve gut morphology, promote beneficial microbiota and activate health-related metabolic pathways in Danzhou broilers.