Antioxidant enzymes: SOD (superoxide dismutase), CAT (catalase), and GSH-Px (glutathione peroxidase). NC (normal control broilers), HC (STZ-induced broilers), and quercetin (0.02%, 0.04% and 0.06%) groups. Statistical analysis was performed by one-way ANOVA followed by Tukey’s test. Values are expressed as means ± S.D. and n = 10. Values with different letters are significantly different P < 0.05 (GSH-Px) and P < 0.01 (CAT).