This experiment studied the effect of Nitric oxide (NO) on the course of parasitic infection from two aspects: one, the amount of NO production in sera of infected goats might exist to be the correlation with antibody at post-infection with Fasciola hepatica. The other, adding L-arginine (the subtrate of NO) into food, whether production of NO might protect Chicken from the infection of Eemirria tenella NO level in sera of goat, detected by chemically reducing enzymic assay, was that the infected group (n5) had difference (P |