Effect of dietary supplementation with different levels of fennel seed (FS) on the productive traits 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: IBW, initial body weight; FBW, final body weight; TFI, total feed intake; BWG, body weight gain; and FCR, feed conversion ratio. Bars express the means ± standard error of means (n = 10 replicate pens per treatment group). P-value of the linear (L) and quadratic (Q) effects of FS levels are indicated for each variable.