Effect of Vitamin A Supplementation on Growth Performance, Lipid Deposition, Antioxidant Ability, and Immunity in Juvenile Chinese Mitten Crab Eriocheir sinensis Fed Diet with Fish Oil Totally Replaced by Palm Oil

This research evaluated the protective effect of vitamin A (VA) on the adverse effect of fish oil (FO) substitution with palm oil (PO) in an economical crab Eriocheir sinensis. Three diets of FO, PO, and PO+8000 IU/kg VA as the main lipid sources were fed to crabs, respectively, for 8 weeks. Compared to crabs fed FO diet, crabs fed PO diet showed reduced hemolymph VA concentration, feed utilization efficiency, and growth performance. Besides, crabs fed PO diet showed elevated lipid content in hepatopancreas and body and triglyceride content in hepatopancreas, leading to decreased antioxidant enzyme and immune parameters activities from biochemical analysis, enzymatic determination, and quantitative polymerase chain reaction. In contrast, compared to crabs fed PO only, VA supplementation in PO improved the growth performance and utilization of fatty acids and reduced lipid deposition in the hepatopancreas. In addition, VA supplementation suppressed gene expression related to triglyceride synthesis (dgat1) and positively affected gene expression related to lipid catabolism (cpt1a, cpt1b, cpt2, and caat). Furthermore, VA supplementation upregulated antioxidant genes (CuZnSOD and CAT) through downregulating gene expression of upstream regulator Keap1. Furthermore, VA supplementation upregulated immune genes (Lzm and proPO) expression and reduced proinflammatory genes (LITAF, ADAM17, and IL-16) expression related to Toll2/MyD88/Relish signaling pathway. This study shows the necessity of VA addition in the feed with FO totally replaced by PO because it can relieve PO's adverse effects and improve the growth of crabs.