Tea tree oil attenuates diquat-induced intestinal barrier dysfunction in chickens via modulating oxidative stress and gut microbiota

This study investigated the effects of tea tree oil (TTO) protective effects against diquat (DIQ)-induced toxicity in chickens. 240 one-day-old Hy-Line W-36 laying chickens randomly allocated to one of two treatment groups: 1) chickens fed a basal diet and 2) chickens fed a diet supplemented with 200 ppm TTO. At 20 days of age, half of the chickens in each group were intraperitoneally injected with DIQ (20 mg per kg body weight), whereas the other half were injected with an equivalent amount of PBS. DIQ significantly reduced serum total antioxidant capacity (T-AOC) (p < 0.001) and suppressed the activities of superoxide dismutase (SOD) (p < 0.001), glutathione peroxidase (GSH-Px) (p < 0.01), and catalase (CAT) (p < 0.01) while elevating malondialdehyde (MDA) levels (p < 0.001). Gut microbiota analysis revealed decreased microbial diversity and dysbiosis following DIQ exposure. Histologically, DIQ reduced villus height (p < 0.01) and villus height to crypt depth ratios (p < 0.01) while increasing crypt depth (p < 0.05) in duodenum, jejunum, and ileum. Tight junction proteins (Claudin-1, Occludin, and ZO-1) were significantly downregulated by DIQ (p < 0.01). Critically, TTO supplementation counteracted these effects by restoring antioxidant enzyme activities (p < 0.01), reducing MDA levels (p < 0.001), modulating gut microbiota dysbiosis, normalizing intestinal morphology, and upregulating tight junction expression (p < 0.05). These results demonstrate TTO mitigates DIQ-induced oxidative stress, modulates gut microbiota equilibrium, and enhances intestinal barrier integrity, supporting its application as a natural feed additive in poultry production.