Dietary phosphatidylcholine improved the survival, growth performance, antioxidant, and osmoregulation ability of early juvenile mud crab Scylla paramamosain

Abstract

A 60-day culture experiment was designed to investigate the effect of dietary phosphatidylcholine/soybean lecithin (PC/SL) levels on survival, growth, body composition, antioxidant, and osmoregulation ability of early juvenile mud crab Scylla paramamosain. Six isonitrogenous and isolipidic experimental diets were formulated with five graded PC levels (0.1% (PC0.1), 0.5% (PC0.5), 1.0% (PC1.0), 2.0% (PC2.0), and 4.0% (PC4.0)) and one SL level (2.0%, SL2.0) to fed early juvenile S. paramamosain (8.70 ± 0.19 mg/crab). The results showed a significantly low survival in the PC0.1 group. Mud crabs obtained the highest growth performance in the PC2.0 and SL2.0 groups, but there was no significant difference with crabs in the PC0.5, PC1.0, and PC4.0 groups. The expression of the target of rapamycin (tor) gene was positively correlated with growth performance. The crab's whole-body crude lipid, triglyceride (TG), and total cholesterol (T-CHO) content rose significantly with increasing dietary PC levels. At the same time, the crab whole-body long-chain polyunsaturated fatty acids (lc-PUFA) proportion increased significantly, accompanied by a decrease in the proportion of C18:2n6. The expression of fatty acid synthesis-related genes decreased significantly with the increase in dietary PC levels. Dietary PC levels ≥1% significantly increased the antioxidant capacity of the mud crabs. Crabs obtained the highest total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activities in the PC1.0 group; the catalase (CAT) activity was positively correlated with dietary PC levels; significantly lower malondialdehyde (MDA) content was found when dietary PC ≥ 1%. Na+/K+-ATPase (NKA) activity increased with increasing dietary PC levels, and the expression of Na+/K+/2Cl−-cotransporter (nkcc) and nka genes were also significantly elevated. The results of the salinity challenge showed that the crabs obtained the highest survival in the PC4.0 group. In summary, the second-order polynomial regression analysis of weight gain and specific growth rate showed that early juvenile S. paramamosain obtained the highest growth at a dietary PC level of 2.60–2.62%.