CLDN4 and Salmonella Infections: In contrast, those alterations in the gut induced by Salmonella infection or VD3 deficiency were restrained by VD3 sufficient administration in our study, as evidenced by downregulating TLR-mediated inflammatory cytokines (TLR4, MyD88, and TNF-a) genes expressions, upregulating Claudin-1 gene and protein, Claudin-4 and ZO-1 protein abundances in the VD-sufficient hens irrespective of Salmonella infection relative to VD deficiency.