2.6. Biochemical analysis

All commercial kits related to antioxidant indicators and hydroxyproline (HYP) kits were obtained from Nanjing Jiancheng Bioengineering Institute (Nanjing, China). The contents of collagen were converted by measuring the content of HYP in muscle, which was calculated by multiplying HYP by 8. The antioxidant indicators included total superoxide dismutase (T-SOD), reactive oxygen species (ROS), protein carbonyl (PC), malondialdehyde (MDA), anti-superoxide anion (ASA), glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx), anti-hydroxyl radical (AHR), catalase (CAT) and total antioxidant capacity (T-AOC). We followed the instructions for the specific operation method. In brief, the muscle sample was weighed and placed in 2-mL centrifuge tube, and then 1.8 mL pre-cooled 0.9% saline was added. The supernatant was collected by centrifugation at 6000 × g for 20 min at 4 °C for further analysis. The methods and kits used are shown in Table S2.