Effects of terrestrial animal fats replacing dietary fish oil on the growth performance, antioxidant capacity and lipid metabolism in juvenile Scylla paramamosain

Abstract

Four experimental diets containing 45% crude protein and 11% crude lipid were formulated by replacing total fish oil (FO) with poultry oil (PO), beef tallow (BT) and lard oil (LO) to evaluate the effects of terrestrial animal fats (TAFs) replacing dietary FO in juvenile green mud crabs (Scylla paramamosain). A total of 120 female juveniles (initial body weight 43.23 ± 0.21 g) was randomly assigned to four diet (three replicates per diet) and stocked into single crab cells (0.23 m × 0.15 m × 0.33 m, width × height × length) with circulating seawater (25–29 °C) for 8 weeks. Compared to FO, crabs fed BT and LO group had about 20% lower weight gain, and significantly lower specific growth rate, feed efficiency and molting ratio, hepatopancreas and muscle lipid, hemolymph total triglyceride contents, and lipase activity, but had approximately 400% higher hepatopancreas aspartate aminotransferase and 100% higher alanine aminotransferase activities. There was no difference in growth performance and feed utilization between PO and other groups. The contents of linoleic acids (18:2n-6) in hepatopancreas and muscle were higher in PO group. TAFs groups had significantly lower docosahexaenoic acids (22:6n-3) and total n-3 polyunsaturated fatty acids contents, as well as lower elongase of very long-chain fatty acids 4, acyl-CoA oxidase 3 and fatty acid transport protein 4 mRNA levels. BT and LO groups had lower mRNA levels of delta-6 fatty acyl desaturase, sterol regulatory element binding protein-1, fatty acid synthase, 6-phosphogluconate dehydrogenase and acetyl-CoA carboxylase. Therefore, dietary BT and LO could reduce the health status and lipid content via decreasing lipase activity, upregulating fatty acid β-oxidation, downregulating lipogenesis and inhibiting the transporting and metabolizing of long chain polyunsaturated fatty acids, thus decrease the growth performance of mud crab. Moreover, PO could be a potential FO substitute for juvenile S. paramamosain.