Effects of dietary EO supplementation on serum biochemical indexes of yellow-feather broilers. (A) Total protein (TP), (B) total cholesterol (TC), (C) triglyceride (TG), (D) high density lipoprotein cholesterol (HDL-C), (E) low density lipoprotein cholesterol (LDL-C), (F) glutamic-pyruvic transaminase (ALT) of serum in yellow-feather broilers on d 21 and 48 were measured by an automatic biochemical analyzer. CON, basic diet; EO200, basic diet contain 200 mg/kg essential oils; EO400, basic diet contain 400 mg/kg essential oils; EO600, basic diet contain 600 mg/kg essential oils. a, b Mean value within a role with no common superscript differ significantly (P < 0.05).