Abstract
Salpingitis in aged laying hens leads to reduced egg production, severely impacting production efficiency. The use of antibiotics poses significant safety risks, necessitating the development of green alternative strategies. This study aimed to investigate the alleviating effects and underlying mechanisms of Lactobacillus agilis on salpingitis in aged laying hens. A 2 × 2 factorial design was employed, in which 192 80-week-old Hy-Line Grey laying hens were randomly allocated into 4 groups with 6 replicates per group and 8 hens per replicate: control group, Lactobacillus agilis group (2 × 10⁸ CFU/hen/day), salpingitis model group (lipopolysaccharide, LPS 3.7 mg/mL + organic chemical reagent, OCR), and salpingitis + Lactobacillus agilis group (2 × 10⁸ CFU/hen/day + LPS 3.7 mg/mL + OCR). The experiment lasted for 8 weeks, and at the end of week 8, salpingitis was induced by cloacal administration of LPS + OCR. The results showed that Lactobacillus agilis significantly alleviated LPS-induced histopathological damage in the oviduct and reduced histopathological scores (P < 0.05). It decreased serum levels of the pro-inflammatory cytokines interleukin‑1β, interleukin‑6 and interleukin‑17A, and increased the levels of the anti-inflammatory cytokine interleukin‑10 and the mucosal antibody secretory immunoglobulin A (P < 0.05). Furthermore, Lactobacillus agilis improved jejunal villus morphology by increasing villus height and the villus height/crypt depth ratio (P < 0.05). It also modulated the cecal microbiota composition, increasing the abundance of beneficial bacteria such as Verrucomicrobiota and Synergistes, while decreasing potentially harmful bacteria such as Fournierella (P < 0.05). In addition, Lactobacillus agilis suppressed the overexpression of genes related to the TLR4/MyD88/NF-κB inflammatory pathway and pyroptosis genes gasdermin E (GSDME) and caspase 1 (CASP1) in oviduct tissue (P < 0.05). Correlation analysis revealed that Verrucomicrobiota and Synergistes were positively correlated with anti-inflammatory cytokines and negatively correlated with oviduct pathological scores, pro-inflammatory cytokines, and genes involved in the TLR4/MyD88/NF-κB pathway and pyroptosis. In conclusion, Lactobacillus agilis alleviates LPS-induced salpingitis by inhibiting the TLR4/MyD88/NF-κB pathway and pyroptosis, thereby regulating inflammatory mediator levels, while concurrently reshaping the cecal microbiota, ultimately alleviating salpingitis and improving intestinal morphology.