This study examined the influence of chlorogenic acid (CGA) on gut antioxidant status, morphology, barrier function, immunity, and cecal microbiota in late-peak laying hens. A total of 240 Hy-Line Brown hens, aged 43 weeks, were randomly assigned to four groups, the basal diet +0, 400, 600, and 800 mg/kg CGA, for 12 weeks. The results revealed that CGA significantly reduced ileal H₂O₂ and malondialdehyde levels; increased duodenal height, ileal villus height, and villus height-to-crypt depth ratio; while decreasing jejunal crypt depth. The 600 and 800 mg/kg CGA significantly upregulated the duodenal, jejunal, and ileal ZO-1 and occludin gene expression; increased IgG levels in serum and ileum; and upregulated ileal IgA gene expression. The 600 mg/kg CGA significantly upregulated CD3D and CD4 gene expression, while downregulating IL-1β gene expression in duodenum, jejunum, and ileum. Moreover, CGA changed the gut microbiota structure. The SCFA-producing bacteria unclassified_f__Peptostreptococcaceae, unclassified_f_Oscillospiraceae, Pseudoflavonifractor, Lachnospiraceae_FCS020_group, Oscillospira, Elusimicrobium, Eubacterium_ventriosum_group, Intestinimonas, and norank_f_Coriobacteriales_Incertae_Sedis were significantly enriched in the 400, 600, and/or 800 mg/kg CGA groups. The bacteria Lactobacillus, Bacillus, and Akkermansia were significantly enriched in the 600 mg/kg CGA group. Conclusively, dietary CGA (600–800 mg/kg) improved intestinal antioxidant status, morphology, barrier and immune function, and beneficial microbiota growth in late-peak laying hens.

This research examined the impact of chlorogenic acid (CGA) on laying performance, antioxidant capacity, egg quality, hepatic inflammation, mitochondrial function, and lipid metabolism in hens subjected to hydrogen peroxide (H₂O₂)-induced oxidative stress (OS). Three hundred sixty healthy 43-wk-old Hy-Line brown hens were randomly assigned to six treatments: a basal diet + 0 (control and H₂O₂), 600 (600 mg/kg CGA and 600 mg/kg CGA + H₂O₂), and 800 (800 mg/kg CGA and 800 mg/kg CGA + H₂O₂) mg/kg CGA for 84 d. On the 64th and 78th days of the trial, hens in groups H₂O₂, 600 mg/kg CGA + H₂O₂, and 800 mg/kg CGA + H₂O₂ were injected intraperitoneally with 10% H₂O₂. The results demonstrated that 600 and 800 mg/kg CGA significantly improved the egg production rate (EPR) and egg quality and reduced lipid peroxidation compared to the control group. The 800 mg/kg CGA showed greater improvements in the EPR and average egg weight (AEW) compared to the 600 mg/kg dose. Conversely, H₂O₂ exposure significantly decreased the EPR, AEW, and egg quality and increased feed conversion rate and average daily feed intake. H₂O₂ exposure significantly decreased serum T-AOC and increased serum MDA levels while reducing hepatic T-SOD, GSH-Px, and CAT activities. Meanwhile, H₂O₂ exposure significantly elevated liver reactive oxygen species levels, pathological damage, and NF-κB, TNFα, and IL-1β gene expression. Additionally, H₂O₂ treatment disrupted hepatocyte mitochondrial structure and significantly increased the expression of VDAC1 protein, and IP3R, GRP75, MCU, Fis1, and MFF genes, while downregulating the expression of MFN2 protein and PGC1α gene. Oil Red O staining demonstrated that H₂O₂ induced significant lipid accumulation in hepatocytes. Concurrently, H₂O₂ significantly increased serum triglycerides, total cholesterol, and liver triglycerides levels while decreasing serum hepatic lipase activity. This was primarily attributed to the significant upregulation of liver SREBP1, FASN, and ACC genes and the downregulation of the liver CPT1 gene induced by H₂O₂. Furthermore, CGA pretreatment effectively prevented the degeneration in laying performance and egg quality, as well as OS, liver inflammation, pathological damage, and mitochondrial dysfunction induced by H₂O₂. CGA inhibited H₂O₂-induced hepatic lipid accumulation by upregulating fatty acid oxidation-related gene expression and downregulating fatty acid synthesis-related gene expression. These findings indicate that the dietary addition of 800 mg/kg of CGA is the optimum supplementation dose. CGA can enhance laying performance and egg quality while alleviating OS, hepatic inflammation, mitochondrial dysfunction, and lipid accumulation in H₂O₂-challenged laying hens.