Dynamic changes of growth, digestion, metabolism, antioxidant and immune ability of Siniperca chuatsi during overwintering

In order to investigate the physiological dynamic changes of growth, digestion, metabolism, antioxidant and immune ability of Siniperca chuatsi during overwintering period, 240 S. chuatsi with body weight of (107.63±0.48) g were selected and divided into growth group and sampling group with four replicates per group and 30 fish per replicate. Feed once every two days for 112 days. During the period, the water temperature experienced a cooling period of 14.5-7.5 °C (0-6 W) and a warming period of 7.5-14.5 °C (6-16 W). 7 sampling points were set at 0, 2 weeks (2 W), 4 weeks (4 W), 6 weeks (6 W), 8 weeks (8 W), 12 weeks (12 W) and 16 weeks (16 W). The results showed S. chuatsi's weight gain rate (WGR), specific growth rate (SGR) and feeding rate (FR) decreased gradually and then increased gradually after reaching the lowest at 6 W. The feed coefficient increased significantly at 6 W and then decreased. The activities of gastric proton pump (H⁺-K⁺-ATPase), intestinal trypsin and amylase increased after the decrease of 6 W. Liver total antioxidant capacity and superoxide dismutase activity decreased significantly at 6 W, while malondialdehyde content increased significantly. Plasma acid phosphatase activity, immunoglobulin content and spleen immunoglobulin content decreased significantly and then increased. The liver structure begins to show partial nuclear migration to the periphery of hepatocytes and vacuolar degeneration at 8 W. At 16 W, S. chuatsi liver cells have irregular morphology and disappeared or even dissolved nuclei. Intestinal villi at 8 W were lower, sparser and irregular than those at 0 W, and the development of intestinal villi at 16 W was better than those at 0 W and 8 W. In conclusion, the digestive, antioxidant and immune abilities of S. siniperca in the early overwintering period are weakened, the body weight of siniperca siniperca in the late overwintering period is significantly increased, and the liver structure and function are seriously damaged. This study can provide a theoretical basis for the management of S. chuatsi feeding and breeding during overwintering, and promote the high-quality development of S. chuatsi farming industry.