BACILLUS STRAINS ALLEVIATE STRESS IN BROILERS Bacillus pumilus TS1 and Bacillus amyloliquefaciens B64 alleviate corticosterone-induced oxidative stress and intestinal injury in broilers

This study investigated the protective effects of Bacillus pumilus TS1 and Bacillus amyloliquefaciens B64 on broilers subjected to corticosterone-induced oxidative stress. A total of 102 one-day-old Arbor Acres broilers were randomly assigned to six treatment groups. Birds received drinking water containing either TS1 or B64 for three weeks, followed by subcutaneous corticosterone administration (4 mg/kg) to induce oxidative stress. Growth performance, antioxidant capacity, intestinal morphology, microbial composition, and expression of intestinal barrier and antioxidant-related genes and proteins were evaluated. Supplementation with TS1 and B64 significantly improved body weight gain compared with corticosterone-treated controls. Both strains enhanced serum total antioxidant capacity and reduced malondialdehyde, lactate dehydrogenase, and creatine kinase levels, indicating mitigation of oxidative damage. Histological analysis revealed that TS1 and B64 protected duodenal and jejunal villus structure and preserved mucosal integrity. 16S rRNA sequencing showed that corticosterone disrupted intestinal microbial balance, while both Bacillus strains restored microbial diversity and increased beneficial genera such as Lactobacillus and Akkermansia . At the molecular level, TS1 and B64 upregulated the transcription and expression of intestinal tight junction proteins (Claudin-1, Claudin-3, ZO-1, and Mucin-2), thereby enhancing barrier function. Both strains activated the KEAP1/NRF2 signaling pathway, evidenced by increased expression of NRF2, HO-1, and NQO1, and suppressed KEAP1 expression, suggesting improved antioxidant defense. Among the two strains, B64 exhibited slightly stronger regulatory effects on antioxidant and tight junction markers. In conclusion, Bacillus pumilus TS1 and Bacillus amyloliquefaciens B64 effectively alleviate corticosterone-induced oxidative stress and intestinal injury in broilers by modulating the intestinal microbiota, enhancing antioxidant capacity, and activating the KEAP1/NRF2 pathway. Supplementation with these Bacillus strains can improve oxidative resilience and intestinal health in broilers under stress, providing a potential alternative to antibiotics for promoting performance and gut integrity in commercial poultry production.