Effects Of Phospholipids Supplementation In Diets On Growth Performance, Digestive And Absorptive Capacities, Intestinal Immune Ability And Physical Barrier Function Of Juvenile Grass Carp(Ctenophaiyngodon Idella)

The effects of dietary phospholipids (PL) on growth performance, digestive and absorptive capacities, intestinal immune ability and physical barrier function of juvenile grass carp(Ctenopharyngodon idella) were assessed. A total of 1080 juvenile grass carp with an average initial weight of 9.34 ± 0.03 g were randomly assigned to six group with three replicates, each replicate has 60 fish. The juvenile grass carp were fed six semi-purified diets containing 0.40%(unsupplemented control group),1.43%.2.38%, 3.29%,4.37% and 5.42% phospholipids for 2 months.The present study showed that optimum PL supplementation significantly increased (P < 0.05) feed intake (FI), feed efficiency (FE), percent weight gain (PWG) as well as protein production value (PPV), lipid production value (LPV) and calcium production value. The activities of trypsin, chymotrypsin, lipase and amylase in hepatopancreas and intestine and activities of alkaline phosphatase (AKP), Na+/K+-ATPase, y-glutamyl transpeptidase and creatine kinase in proximal intestine (PI), mid intestine (MI)and distal intestine (DI) were significantly increased with optimum PL supplementation (P< 0.05). Meanwhile, optimum PL supplementation significantly enhanced the relative mRNA expression of trypsinogen 2, chymotrypsinogen, and amylase in hepatopancreas, Na+/K+-ATPase alpha subunit isoform 1(atplala.1), Na+/K+-ATPase alpha subunit isoform 8 (atp1a1a.4) and creatine kinase genes in three intestinal segments, and relative mRNA expression of target of rapamycin (TOR), ribosomal protein S6 kinase 1 (S6K1) and casein kinase 2 (CK2) in PI, MI, DI and hepatopancreas. Moreover, results indicated that optimum PL supplementation increased lysozyme (LZ), acid phosphatase (ACP) activities and complement component 3 (C3) content in three intestinal segments (P< 0.05), up-regulated mRNA levels of interleukin 10 (IL-10), transforming growth factor β1 (TGF-β1), and IκBα (P< 0.05), and down-regulated tumor necrosis factor a, interleukin 1β, nuclear factor κB p65 (NF-κB p65), IKKβ and IKKγ gene expression (P.< 0.05). In addition, optimum PL supplementation decreased malondialdehyde (MDA), protein carbonyl (PC) and reactive oxygen species (ROS) content (P< 0.05), and increased the activities of anti-superoxide anion (ASA), anti-hydroxyl radical (AHR), copper/zinc superoxide dismutase (SOD1), glutathione peroxidase (GPx) and glutathione reductase (GR), and glutathione content in the intestine (P< 0.05). Furthermore, the relative mRNA expression of occludin, ZO-1, claudin3, claudin b, claudin c, claudin 12, SOD1, GPx, GR and NF-E2-related factor 2 (Nrf2) in the intestine were increased, and the relative mRNA expression of Kelch-like-ECH-associated protein 1a (Keap1a) were decreased with increasing of dietary PL up to a certain point (P< 0.05).In conclusion, optimum dietary PL improves digestive and absorptive capacities, intestinal immune ability, physical barrier function and and related singling molecules of juvenile grass carp. Based on the quadratic regression analysis for PWG, trypsin activity in hepatopancreas and AKP activity in the PI, the optimal dietary PL level for juvenile grass carp (9.34-87.50 g) was estimated to be 3.46%,3.56% and 3.18%, respectively.