Dietary pyrroloquinoline quinone supplementation improves productive performance, immunity, and intestinal health in late-phase Jingfen No. 6 laying hens.

This study evaluated the effects of dietary pyrroloquinoline quinone (PQQ) on the productive performance, biochemical parameters, immune function, and intestinal health of laying hens during the late laying period. A total of 360 Jingfen No. 6 laying hens, aged 48 weeks, were randomly assigned to 5 dietary treatments (0, 0.5, 1.0, 2.0, and 4.0 mg/kg PQQ), with 6 replicates per treatment and 12 birds per replicate. Egg production performance, serum antibody titers, blood biochemical and immune indices, intestinal morphology, tight junction protein expression, and cecal microbiota and metabolite profiles were determined. The results showed that dietary supplementation with 0.5 and 1.0 mg/kg PQQ increased average daily egg mass and egg production rate (P < 0.01) and decreased the feed-to-egg ratio (P < 0.01). PQQ reduced serum malondialdehyde (MDA) and lactate dehydrogenase (LDH) levels (P < 0.05), alongside a significant increase in catalase (CAT) activity (P < 0.05). Antibody titers against H5, H7, and NDV were elevated in all PQQ-treated groups, with significant differences for H5 and NDV antibodies at 0.5 and 1.0 mg/kg groups (P < 0.05) and H7 antibodies in the 0.5 mg/kg group (P < 0.05). PQQ supplementation increased intestinal mucosal secretory immunoglobulin A (sIgA) content (P < 0.05), decreased serum interleukin-6 (IL-6) levels across all treatment doses (P < 0.01), and reduced IL-10 concentrations at 1.0 mg/kg (P < 0.05). Morphological analysis revealed that PQQ significantly increased jejunal villus height and the villus height-to-crypt depth ratio (P < 0.05 and P < 0.01), while upregulating mRNA expression of the tight junction proteins ZO-1 and Occludin (P < 0.05). PQQ significantly enhanced the relative abundance of beneficial bacterial genera including Prevotellaceae_Ga6A1_group, Lactobacillus, and Faecalibacterium. Metabolomic analysis revealed that PQQ predominantly upregulated intestinal organic acids including 6-(Pyridin-3-YL)hexanoic acid, DL-Valine-4-antipyrineamide, Eicosadienic acid, 2-methyl-hexadecanoic acid, and Penicilloic acid, while downregulating lipid metabolites including Triglycerides (TG), Phosphatidylglycerol (PG), and Phosphatidylcholine (PC). In conclusion, 0.5 to 1.0 mg/kg PQQ is optimal for enhancing productivity and antibody production in the late-phase laying hens through minimized oxidative damage, attenuated inflammation, and restructured intestinal microbiota and metabolic profiles.