Abstract
A total of 180 one-day-old white-feathered broiler chicks were selected and randomly divided into 4 treatments, namely the control group (CON), Escherichia coli groups (E. coli), 2 g/kg polyherbal mixture group (PHM2), and the 4 g/kg polyherbal mixture group (PHM4). The CON and E. coli groups were fed a basal diet, while the PHM2 and PHM4 groups were fed the basal diet supplemented with 2 g/kg and 4 g/kg PHM, respectively. Each group had 3 replicates, with 15 broilers per replicate. On day 17 of the experiment, broilers in the E. coli, PHM2, and PHM4 groups were intraperitoneally injected with 0.8 mL of 1 × 10(8) CFU/mL of E. coli O78. Broilers in the control group received an equivalent volume of saline. Chicks were euthanized 48 h postinjection for collecting serum, liver, spleen, jejunum, ileum, ileal mucosa, and cecal contents. Our results showed that PHM significantly reversed the weight loss and decreased the diarrhea rate and the mortality of chicks caused by E. coli infection (P < 0.05). In the serum of chicks infected with E. coli, PHM significantly enhanced the antioxidant capacity (P < 0.05), increased the levels of immunoglobulins and anti-inflammatory cytokines (P < 0.05), and decreased the concentrations of proinflammatory cytokines (P < 0.05). Meanwhile, PHM also promoted the mRNA expression of antioxidant-related genes and decreased the expression of proinflammatory cytokines and apoptosis-related genes in the liver, spleen, jejunum, and ileum (P < 0.05). In addition, PHM repaired the intestinal barrier and injury to further reduce the serum concentrations of d-lactate (DAO) and lipopolysaccharide (LPS) (P < 0.05). More importantly, PHM significantly regulated the composition of cecal microbiota, especially by up-regulating the relative abundance of beneficial bacteria, including Faecalibacterium, Bacteroides, Butyricicoccus, and Lactobacillus, and down-regulating the relative abundance of pathogenic bacteria, including Enterococcus, Escherichia, and Shigella (P < 0.05). These beneficial bacteria were significantly positively correlated with antioxidant capacity and intestinal barrier function, while pathogenic bacteria were significantly positively correlated with proinflammatory cytokines (P < 0.05). In conclusion, PHM may be a potential preventive strategy for E. coli-infected poultry, which is closely related to its modulation of gut microbiota.