Metabolic and nutritional effects of vitamin A on growth, lipid metabolism, antioxidant capacity and hepatopancreas health of juvenile mud crab (Scylla paramamosain)

An 8-week feeding trial was conducted to determine the effects of different vitamin A (VA) level on growth performance, lipid metabolism, antioxidant capacity and hepatopancreas health of juvenile mud crab ( Scylla paramamosain ). Six experimental diets with different VA level were created, and the actual VA analysis values were 0.00, 2.52, 5.40, 11.59, 18.68 and 38.18 mg/kg, respectively. A total of 180 disease-free crabs weighing 15.03 ± 0.01 g were randomly transferred to 180 independent baskets, each treatment consisting of 3 replicates, with 10 crabs in each replicate. The results indicated that dietary 5.40 mg/kg VA significantly improved the FW, PWG, SGR and MR of juvenile mud crab. Crabs fed diet containing 5.40 mg/kg VA exhibited the highest concentrations of T-CHO, HDL-C and LDL-C and the activity of T-AOC in hemolymph, the activities of GSH-PX and T-SOD in hepatopancreas, and the expressions of fatp4 , cptⅠ , Δ6 fad and elovl6 in hepatopancreas were significantly up-regulated, while the hepatopancreas MDA concentration was the lowest ( P < 0.05). Besides, dietary 38.18 mg/kg VA up-regulated the expressions of relish , rab6a and bax , while significantly down-regulated the expressions of alf-3 and bcl-2 . The correlation analysis results showed that fatp4 and gpx both have a significant positive correlation with growth performance related parameters, suggesting they may be crucial for VA's physiological functions. In conclusion, the broken-line equations of PWG relative to the dietary VA level indicated that the optimal dietary VA requirement for juvenile mud crab was established as 2.96 mg/kg. Dietary 5.40 mg/kg VA could improve the growth performance, lipid metabolism and antioxidant capacity of juvenile mud crab, meanwhile avoid hepatopancreas damage, inflammatory response and apoptosis caused by excessive VA. • Dietary 5.40 mg/kg vitamin A promoted the growth performance of juvenile mud crab. • Dietary 5.40 mg/kg vitamin A improved the lipid metabolism of juvenile mud crab. • Dietary 5.40 mg/kg vitamin A enhanced the antioxidant capacity of juvenile mud crab. • Dietary 38.18 mg/kg vitamin A would cause hepatopancreas damage, inflammatory response and apoptosis. • The optimal dietary vitamin A requirement was estimated to be 2.96–5.40 mg/kg.