Dietary gallic acid supplementation alleviates LPS-induced inflammatory responses and intestinal barrier damage in chickens at an early age

This study was conducted to investigate the effects of dietary gallic acid (GA) supplementation on growth performance and intestinal barrier function of broiler chickens challenged with lipopolysaccharide (LPS). A total of 750 1-day-old "817" male crossbred broilers were randomly assigned to 5 treatment groups, with six replicates per group: basal diet (CON), basal diet following LPS-challenge (LPS), and basal diet supplemented with 150, 300, 450 mg/kg GA following LPS-challenge (GA150, GA300, and GA450). On days 14, 17, and 20, chickens in the LPS, GA150, GA300, and GA450 groups received intraperitoneal injections of LPS, while chickens in the CON group received the same dose of saline. The results showed that, compared with broilers in CON, dietary supplementation with GA eliminated the negative effects of LPS on reducing BW on day 21, as well as the 1 to 21d ADFI and ADG compared to broilers in CON group ( P < 0.05). Compared with the LPS group, dietary supplementation with 300 and 450 mg/kg GA significantly upregulated the relative expression of superoxide dismutase1 ( SOD1 ), and 150 mg/kg GA significantly upregulated the relative expression of glutathione peroxidase 1 ( GPX1 ) in ileal mucosa. Compared with the LPS group, dietary GA supplementation significantly increased the percentages of CD3 + and CD4 + T cells in the ileum, while decreased the percentage of BU-1 + B cells (P < 0.05). In addition, the plasma content of TNF-α was significantly increased under LPS stimulation. Supplementation with 150 and 300 mg/kg GA increased the levels of IL-10 and TGF-β, reduced the level of TNF-α in plasma, and upregulated the relative expression of occludin ( OCLN ) and mucin 2 ( MUC2 ) in the ileal mucosa ( P < 0.05). Compared with the CON group, LPS challenge significantly increased the crypt depth in the ileum ( P < 0.05). However, supplementation with GA significantly increased the villus height and the villus height-to-crypt depth ratio (VCR) while significantly decreasing crypt depth after LPS challenge ( P < 0.05). Firmicutes was the dominant phylum in cecal microbiota; LPS stimulation disrupted cecal microbial homeostasis, while GA exerted dose-dependent differential regulatory effects on this LPS-induced dysbiosis: 150 and 300 mg/kg GA alleviated the LPS-induced reduction in Bacteroides abundance, and 450 mg/kg GA modulated the abundance of Proteobacteria and multiple relevant bacterial genera. In conclusion, dietary GA supplementation up-regulated the expression of antioxidant-related genes in the ileal mucosa, modulated immune function, and alleviated LPS-induced intestinal barrier damage and gut dysbiosis, thereby improving the growth performance of broilers challenged with LPS.