TLR4 and Salmonella Infections: As displayed in Table 3, Salmonella infection didn't affect intestinal VD-metabolism related genes expression, but remarkably upregulated toll-like receptor (TLR)-4, tumor necrosis factor (TNF)-α, interleukin (IL)-8, and interferon (IFN)-γ genes expression (P < 0.05), tended to up-regulate genes expressions of myeloid differentiation primary response protein 88 (MyD88) and IL-1β (0.05 < P < 0.1) as compared to the non-infected hens, suggesting that Salmonella infection caused intestinal inflammation via activating TLR4-mediated pathway.