Fig. 3. Antioxidant index values in duck spleen. (A) Malondialdehyde (MDA) levels. (B) Xanthine oxidase (XOD) activities. (C) Catalase (CAT) activities. Different lowercase letters are significantly different between groups (p < 0.05), different uppercase letters are highly significantly different between groups (p < 0.01), and common lowercase or uppercase letters are not significantly different between groups (p > 0.05). Each value represents the mean ± SEM.