The influence of dietary arachidonic acid on growth performance, fatty acid composition and antioxidant capacity on postlarva of mud crab Scylla paramamosain

An eight-week feeding trial was conducted to evaluate the influence of dietary arachidonic acid (20:4n-6) on growth performance, fatty acid composition and antioxidant capacity on postlarva mud crab (Scylla paramamosain). Five isonitrogenous and isoenergetic diets with 0.34% (the control diet), 0.48%, 0.84%, 1.18% and 1.81% ARA levels were formulated by adding ARA rich oil in the basal diet. There were triplicate groups of 28 postlarval crabs (initial weight 8.15 mg) for each diet treatment. The results indicated that crabs fed diets with 1.18% ARA showed significantly higher final body weight (FBW), weight gain (WG) as well as specific growth rate (SGR) than the other groups. Survival, molting frequency (MF) and intermoult period were not significantly affected by different dietary ARA addition. Compared with the stable DHA content in crab, the EPA content decreased significantly with increase of dietary ARA addition. In crabs, superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) activities generally increased with dietary ARA supplementation, and were highest in 1.18% dietary ARA group. The MDA (malondialdehyde) concentrations showed the opposite trend. In addition, with the increase of dietary ARA content, the relatively increased lipid content in body composition was observed. The gene expression of fatty acid synthase (fas) and fatty acid binding protein-3 (fabp-3) in crabs increased with increasing ARA level in diets (0.34–1.18%) and then down-regulated expression levels with further ARA addition (1.81%). These results suggested that moderate dietary ARA level (1.18%) contributed to the improvement of growth performance and antioxidant capacity, and regulated the fatty acid composition and gene expression of some lipid metabolism in crabs, while excessive ARA addition in diets may cause oxidative stress of postlarval Scylla paramamosain. Moreover, the dietary ARA/EPA ratio of 1.82 may be suitable for the growth of postlarval Scylla paramamosain.