Effects of swimming activity and feed restriction on antioxidant and digestive enzymes in juvenile rainbow trout: Implications for nutritional and exercise strategies in aquaculture

Abstract Background In this study, we investigated the effects of swimming activity and feed restriction on digestion and antioxidant enzyme activities in juvenile rainbow trout (average body weight of 26.54 ± 0.36 g). Methods The stomach, liver and kidney tissues were obtained from four distinct groups: the static water group (fish were kept in static water and fed to satiation), the feeding restricted group (fish were kept in static water with a 25% feed restriction), the swimming exercised group (fish were forced to swimming at a flow rate of 1 Body Length per second (BL/s)) and the swimming exercised‐feed restricted group (subjected to swimming exercise at a 1 BL/s flow rate along with a 25% feed restriction). We determined the levels of glutathione, lipid peroxidation and the activities of catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, glucose‐6‐phosphate dehydrogenase and lactate dehydrogenase, as well as the presence of reactive oxygen species in the tissues obtained from the fish. Additionally, the activities of pepsin, protease, lipase and arginase in these tissues were measured. Results Swimming activity and feed restriction showed different effects on the enzyme activities of the fish in the experimental groups. Conclusion It can be concluded that proper nutrition and exercise positively influence the antioxidant system and enzyme activities in fish, reducing the formation of free radicals. This situation is likely to contribute to the fish's development.