Effect of dietary supplementation with different levels of fennel seed (FS) on the plasma biochemicals of broilers. Treatment groups: C, FS10, FS20, and FS30 indicate the supplementation of fennel seed at the rate of 0, 10, 20, and 30 g/kg of diet, respectively. Variables: TP, total protein; T3, triiodothyronine hormone; ALT, alanine aminotransferase enzyme; AST, aspartate aminotransferase enzyme; and UA, uric acid. Bars express the means ± standard error of means (n = 20 samples per treatment group). P-value of the linear (L) and quadratic (Q) effects of FS levels are indicated for each variable.