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A 56‐day feeding experiment was performed to investigate the effects of the dietary lipid level on the survival, growth performance, digestive enzyme activities and antioxidant capacity of Eriocheir sinensis reared under three salinities. Six feeds with graded levels of lipids (5%, 7%, 9%, 11%, 13% and 15%) were formulated by including fish oil as the main lipid source. Sixty crab individuals (initial weight: 0.21 ± 0.02 g) were assigned to each aquarium. In total, 18 aquariums were distributed under each salinity condition. Each feed was randomly allocated to three parallel tanks of crabs. The feeding experiment lasted for 56 days. Results showed that the survival rate of E. sinensis fed diets with 7%–15% lipids just showed a decreasing tendency as the salinity increased. The highest weight gain rate (WGR) was found in the treatment with 11%, 9% and 5% lipid at the salinity of 0.5‰, 2‰ and 6‰ respectively. At the salinity of 0.5‰, 2‰ and 6‰, the highest activities of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase) were detected in the treatments with 11%, 13% and 7% lipid respectively. As the salinity increased, the protein and lipid contents showed an increasing trend, while the moisture content showed an opposite trend. At each salinity, arachidonic acid and docosahexaenoic acid increased, while saturated fatty acids and monounsaturated fatty acids decreased with the increase of dietary lipid level. These results indicated that increasing salinity resulted in decreased antioxidant enzyme activities and increased malondialdehyde content in the juvenile E. sinensis, especially when they were fed diets with relatively higher lipid level. Based on WGR, digestive enzyme activity and antioxidant capacity, the optimal lipid level was estimated to be 8.28–13%, 7.54–13% and 5–8.89% for juvenile E. sinensis reared at the salinity of 0.5‰, 2‰ and 6‰ respectively. [ABSTRACT FROM AUTHOR]

A 60‐day feeding experiment was performed to investigate the survival, growth, body composition, antioxidant capacity and related gene expression of Eriocheirsinensis which were fed diets with different lipid sources under three salinities. Five feeds were formulated with one of the candidate oils (fish oil, soybean oil, linseed oil, colza oil or palm oil) and were named FO, SO, LO, CO or PO respectively. Results showed that the survival rate (SR) of E. sinensis showed a decreasing tendency as the salinity increased. But SR was not significantly affected by dietary lipid sources at each salinity. Weight gain rate (WGR) were highest in the treatment of FO/PO at a salinity of 0.5‰, CO/FO/SO at a salinity of 2‰ and LO at a salinity of 6‰ respectively. At salinities of 0.5‰ and 2‰, the transcription of pro‐inflammatory and antioxidant genes in LO was significantly higher than that in FO or PO. While at a salinity of 6‰, the transcription of detected genes in FO was markedly increased compared to that in the vegetable oil treatments. At each salinity, the eicosapentaenoic acid (EPA) contents showed comparable values among different dietary treatments. However, the docosahexaenoic acid (DHA) contents in E. sinensis fed the diets with FO were still significantly higher than those with vegetable oils. These results showed that increasing salinity decreased the antioxidant capacity and therefore negatively affected the survival and growth rates of experimental animals. The beneficial effects of FO on survival and growth performance were eliminated by increasing the salinity to 6‰, which could be due to the increased lipid peroxidation and inflammatory response caused by salinity stress. It was concluded that at the salinity of 0.5‰ and 2‰, the recommended lipid sources were FO/PO and CO/FO/SO respectively. While at the salinity of 6‰, LO was the most ideal lipid source for juvenile E. sinensis. [ABSTRACT FROM AUTHOR]