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The shortage of fishmeal is the main restrictive factor for developing aquaculture, which impedes economic and social development in many countries, including China. Compare to protein, lipid was regarded as the cheaper energy resource, especially to carnivorous fish, which prefer lipid rather than carbohydrate (Council, 2011).Lipid is one of the primary nutrients in natural feed and an indispensable ingredient in high-efficiency compound feed. Previous studies showed that increasing dietary lipids enhanced growth performance and fed utilization in fish, which indicated that lipids had the function of protein sparing (Vergara et al., 1999). However, high-level lipid will inhibit the growth performance, and increase fat deposition in fish, leading to degeneration, necrosis of stem cells,

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In this manuscript, three iso‐nitrogenous and iso‐lipidic diets containing 50, 150 and 250 g/kg of fishmeal (FM) were fed white shrimp Litopenaeus vannamei for 8 weeks. At the end of feeding, survival and percentage weight gain of shrimp were examined. Hepatopancreas and haemolymph were sampled, activities of superoxide dismutase (SOD) and catalase (CAT), nitric oxide (NO), glutathione (GSH) and malondialdehyde (MDA) levels in hepatopancreas, activities of SOD, CAT, acid phosphatase (ACP) and alkaline phosphatase (AKP), and NO, GSH, MDA in haemolymph were examined. Haemolymph was further subjected to GC‐MS analysis. Results indicated that no significant differences in survival rate and percentage weight gain were observed among three treatments. SOD activity and GSH levels in hepatopancreas, and CAT activity, AKP activity, GSH and MDA levels in haemolymph were significantly lower in shrimp fed 50 g/kg FM diet. GC‐MS analysis of haemolymph indicated that 81 metabolites were significantly altered in the three groups. Furthermore, 8 metabolism pathways were significantly influenced by dietary FM levels. In conclusion, dietary administration of 50 g/kg FM resulted in inhibition of antioxidant ability, and disordered the energy metabolism, one‐carbon metabolism and unsaturated fatty acid metabolism in shrimp.

Filamentous microalga Klebsormidium sp. has huge potential to become a natural and healthy additive in aquatic feed since it contains various bioactive nutrients, such as linoleic acid (LA), carotenoids, and chlorophylls. Therefore, an eight-week feeding experiment was performed to evaluate the effects of dietary Klebsormidium sp. on the growth performance, antioxidant and anti-inflammatory status, metabolism, and mid-intestine morphology of Litopenaeus vannamei. Two isonitrogenous and isolipid diets supplemented with and without 5% Klebsormidium sp. were prepared. Results showed that L. vannamei fed with Klebsormidium sp. had better growth performance and feed utilization by optimizing mid-intestine morphology and improving the carbohydrate metabolism. In addition, Klebsormidium sp. also enhanced the antioxidant capacity of L. vannamei by downregulating antioxidant parameters (hepatopancreas T-SOD, hepatopancreas GSH-PX, hemolymph T-SOD, hemolymph MDA) and RNA expression levels of antioxidant genes (gsh-px and cat). Furthermore, the supplementations of dietary Klebsormidium sp. significantly improved hepatopancreas health by downregulating RNA expression levels of pro-inflammatory related genes (relish and rho). Therefore, a dose of 5% Klebsormidium sp. is recommended for the daily diet of L. vannamei to improve the growth performance, antioxidant and anti-inflammatory status, metabolism, and mid-intestine morphology of shrimp.