Abstract
Background: In order to obtain the suitable lipid requirements of rainbow trout (Oncorhynchus mykiss) cultured in the recirculating aquaculture systems (RAS), the effects of dietary lipid levels on fat-related physiological metabolism and antioxidant defenses were investigated. Four isonitrogenous diets containing 45% crude protein with increasing dietary lipid levels of 12%, 15%, 18%, and 21% were fed to 360 fish with initial body weight of 333.25 ± 20.71 g for 77 d. Results: The results showed that a high lipid diet increased lipase and amylase activities in trout livers, whereas a low lipid diet improved lipase and alkaline phosphatase activities in trout intestines. Meanwhile, increased dietary lipid levels elevated low density lipoprotein content and decreased high density lipoprotein, triglyceride, total cholesterol concentrations and the high density lipoprotein/low density lipoprotein ratio in serum. Moreover, increases in superoxide dismutase, glutathione, and malondialdehyde activities were observed in serum with increasing dietary lipid levels, while catalase activity and the catalase/superoxide dismutase ratio decreased. Conclusion: These results indicate that rainbow trout fed diets with low and medium fat levels received adequate fat nutrition and that the diets ensured healthy growth by improving digestive absorption, fat synthesis and transport, and antioxidant levels, and the L12 group had the best growth performance. In conclusion, rainbow trout are healthier when fed diets with approximately 12% lipid levels in RAS.
Physiological Metabolism and Antioxidant Capacity of Rainbow Trout (Oncorhynchus Mykiss) Fed Diets with Different Lipid Levels
