The gene expression of iNOS was also significantly increased following H9N2 AIV infection (P < 0.01; Figure 6C), while that of TNF-α, IFN-γ and iNOS was significantly downregulated in the H9N2 AIV infection group with AL feeding, as compared with the infection group (P < 0.01 and P < 0.05, Figures 6A–C). This evidence concerns the gene NOS2 and infection.