Effects of dietary Vitamin E on growth, immune- and ovarian development-associated physiological and molecular responses in red swamp crayfish (Procambarus clarkii)

This experiment investigated the effects of different levels of Vitamin E addition on the growth, immunity, and ovarian development of red swamp crayfish ( Procambarus clarkii ). A total of 720 crayfish (8.14 ± 0.05 g) were selected and divided into six groups, with four replicates per treatment. The experimental diets with Vitamin E addition amounts of 0 mg/kg (E0), 50 mg/kg (E1), 100 mg/kg (E2), 200 mg/kg (E3), 400 mg/kg (E4), and 1000 mg/kg (E5) were fed to crayfish for 56 days. Dietary supplementation with 100–200 mg/kg Vitamin E significantly improved weight gain rate (WGR) and specific growth rate compared with the diet without Vitamin E (0 mg/kg) ( P < 0.05). Lipase and amylase activities in the hepatopancreas and intestine reached their peak in the 200 mg/kg group. Histological observations indicated more intact and better-organized hepatopancreas and intestinal structures in the 100–200 mg/kg groups. Serum lipid profiles were improved in the 200 mg/kg group, characterized by lower triglyceride and low-density lipoprotein cholesterol levels, and higher high-density lipoprotein cholesterol levels ( P < 0.05). Supplementation with 200 mg/kg Vitamin E significantly increased serum acid phosphatase and lysozyme activities, and decreased alanine aminotransferase activity compared with the 0 mg/kg group ( P < 0.05). In terms of lipid metabolism, the 200 mg/kg Vitamin E exhibited upregulated expression of lipid synthesis-related genes ( fas , srebp1 , acsbg , acc2 ) and lipid transport-related genes ( fab p, fatp ), and downregulated expression of lipid decomposition-related genes ( cpt-1 , atgl , aco , pla2 ) (P < 0.05). Dietary supplementation of 200 mg/kg Vitamin E upregulated and downregulated the expression of molting-promoting ( mtor and s6k1 ) genes and -inhibiting ( 4ebp1 and mih ) genes, respectively. Regarding ovarian development, adding 200 mg/kg of Vitamin E can upregulate the mRNA levels of pka , fox l2 , vg , cdc2 , and cyclin b . In conclusion, dietary vitamin E exerts a dose-dependent effect on the growth performance and major physiological parameters of P. clarkii . Based on the WGR and feed conversion ratio, a supplementation level of 128.3771–142.5556 mg/kg Vitamin E is recommended to meet its growth and physiological requirements. • An appropriate Vitamin E addition could optimize the digestive capacity to improve the growth of crayfish. • Dietary Vitamin E can promote molting through activating the MIH and mTOR signaling pathways. • Vitamin E enhanced the antioxidant capacity and immunity of crayfish by increasing antioxidant-related enzyme activities and the TLR pathway. • Vitamin E regulated vitellogenin synthesis in crayfish via the RXR/EcR-Vg pathway, thereby promoting gonadal development.