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¹ College of Fisheries, Huazhong Agricultural University 1Engineering Research Center of Green development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education 1Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture 1Hubei Provincial Engineering Laboratory for Pond Aquaculture, Wuhan 430070, China
² State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
³ Hubei Vocational College of Bio-technology, Wuhan 430070, China DOI : 10.4194/TRJFAS25334 Viewed : 52 - Downloaded : 66 The aim of this study was to assess the optimal protein level for grass carp when using Chlorella vulgaris meal (CVM) as a sole protein source. Six diets (CVM35, CVM42, CVM49, CVM55, CVM62, and CVM69) with varying protein levels (21.51%, 24.95%, 29.16%, 32.75%, 36.79%, and 39.74%, respectively) were fed to triplicate tanks with 30 fish each (7.0±0.1 g) for 8 weeks. Results indicated the FBW and SGR increased first and then plateaued as dietary protein level increased, while the FR plateaued first and then decreased. The FE and HSI increased linearly with dietary protein level, while VSI and MFI decreased linearly (P<0.05). As dietary protein level increased, serum IgM and GSH-Px first increased and then decreased, and peaked in the CVM55 group, while MDA showed the opposite trend. High protein diets (CVM62 and CVM69) significantly activated mTOR signaling and altered fish proximate composition. Moreover, optimal protein diet enhanced fish hardness and regulated the expression of genes associated with myosin types (myh7, myh1, myh2, and myh4) and muscle development (MRFs, FGF6s and mstn). An optimal dietary protein level of 36.54% was recommended for juvenile grass carp based on the SGR using CVM as protein source. Keywords : Chlorella vulgaris Grass carp Growth performance Meat quality Myosin Heavy chains