Effects Of Mannan Oligosaccharide On The Production Performance And The Function And Mechanism Of Immune Organ Health In Young Grass Carp(Ctenopharyngodon Idella)

This study was designed to evaluated the effects of dietary mannan oligosaccharide(MOS)supplementation on the growth prefermance and organism immunity,as well as its mechanisms in young grass carp(Ctenopharyngodon idella).A total of 540 young grass carp(215.85 ± 0.30 g)were randomly distributed into six groups and fed six diets containing graded levels of mannan oligosaccharide supplementation at 0,200,400,600,800 and 1000 mg/kg diet for 60 days to investigate the effects of MOS supplementation on the fish growth performance.After the feeding trial,a challenge test was conducted for 14 days to investigate the effects of MOS supplementation structural integrity and immune function in the head kidney,spleen and skin.This result indicated that MOS supplementation increased growth performance(PWG,SGR and FE)and improved structural integrity and immune function on head kidney,spleen and skin of young grass carp.On the one hand,MOS supplementation enhanced antioxidant capacity via activating NF-E2-related factor 2 which up-regulated m RNA levels of antioxidant enzymes(such as Mn SOD,CAT and GST)and increased related enzyme activity,lowered apoptosis via inhibiting p38 mitogen-activated protein kinase [not JNK(except skin)] m RNA levels which activate the apoptosis-related factors(such as Mcl-1,Bcl-2,IAP)and inhibited m RNA levels of Caspases(such as Caspase-3,Caspase-7 and Caspase-8)to reduce cell apoptosis,inhibited m RNA levels of MLCK and up-regulated m RNA levels of TJs(such as ZO-1 and Claudins)[not Claudin-3c(except skin)and Claudin-b].On the other hand,MOS supplementation incresed antibacterial substance(such as LZ and ACP)and up-regulated the m RNA levels of antimicrobial peptide(such as LEAP-2,?-defensin and hepcidin),activated target of rapamycin/ ribosomal S6 protein kinase1 signal pathway,up-regulated anti-inflammatory cytokine(such as transforming growth factor ?,interleukin-10 and interleukin-11)and inhibited m RNA levels of IKK(not IKK?)and down-regulated proinflammatory cytokine(such as tumor necrosis factor ?,IL-12p40 and IL-17D)m RNA levels to reduce inflammatory response.The results of the growth trial showed that dietary MOS supplementation could elevate the growth performance,maintain structural integrity and immune function on the head kidney,spleen and skin of young grass carp.Based on PWG,head kidney C3 contents,spleen MDA contents and skin ROS contents,the dietary MOS supplementation for young grass carp(216-854 g)are estimated to be 428.5,575,519.3 and 553.5 mg/kg,respectively.