ResultsAs shown in Table 2, biochemical blood variables were affected by treatments, except AST. In comparison with controls,the concentrations of TG, TC and LDL linearly decreased in birds received graded levels of dietary peppermint, whereas HDLlevel increased (P < 0.001). Although AST level were not affected by dietary treatments, ALT level in peppermint groups waslower than that in negative control (P < 0.001).