Effect of different levels of MAG in serum parameters of laying hens. Data represent means±SD, one-way ANOVA, and different letters represent statistically significant differences (P < 0.05). ALT, alanine aminotransferase; AST, aspartate transaminase; ALP, alkaline phosphatase; T-AOC, total antioxidant capacity; T-SOD, total-superoxide dismutase; MDA, malondialdehyde; CAT, malondialdehyde; TG, serum triglycerides.