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 four 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 weeks. The chicks
were raised in floor pens inside the broiler farm at a temperature and humidity index (THI) of 29
from day 21 to day 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 generelated
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.