Abstract
Intestinal oxidative stress in broilers is produced by chronic heat stress (HS) and has a negative impact on poultry performance as it induces intestinal inflammation and promotes the invasion of gram-negative bacteria, such as bacterial lipopolysaccharide (LPS). Therefore, dietary inclusion of the antioxidant compound, ethoxyquin (EQ), could improve enteric antioxidant capacity, immune responses, and the epithelial barrier, and maintain the symbiotic gut microbiota community. To investigate the effects of EQ supplementation on alleviating enteric oxidative stress in heat-stressed broilers, 200 one-day-old male Ross 308 broilers were randomly assigned to 4 groups (n = 50 chicks/group; n = 10 chicks/replicate) and fed a basal diet supplemented with 0 (CT), 50 (EQ-50), 100 (EQ-100), and 200 (EQ-200) mg EQ/ kg(-1) for 5 wk. The chicks were raised in floor pens inside the broiler farm at a temperature and humidity index (THI) of 29 from d 21 to d 35. Growth performance traits, relative organ index, hepatic antioxidant enzymes, serum immunity, total adenylate, and cytokine activities were improved in the EQ-50 group (linear or quadratic P < 0.05), promoting the relative mRNA expression of cytokine gene-related anti-inflammatory and growth factors. A distinct microbial community colonised the gut microbiota in the EQ-50 group, with a high relative abundance of Lactobacillus, Ligilactobacillus, Limosilactobacillus, Pediococcus, Blautia, and Faecalibacterium compared to the other groups. Dietary supplementation with 50 mg EQ/ kg(-1) for 5 wk attenuates enteric oxidative stress and intestinal inflammation by enhancing serum immune and cytokine content (IgG, IL-6, and TGF-β,) and symbiotic microbiota in heat-stressed broilers. EQ promotes the expression of Hsp70, SOD2, GPx 4, IL-6, and IGF-1 cytokine gene-related anti-inflammatory and growth factors in heat-stressed hepatic broilers. Collectively, EQ-50 could be a suitable feed supplement for attenuating enteric oxidative stress and intestinal inflammation, thereby promoting the productivity of heat-stressed broilers.