The Interaction Of Dietary Niacin And Lipid Affect The Growth,Antioxidant Capacity And Lipid Metabolism Of Female Eriocheir Sinensis

Niacin is a direct precursor of the coenzymes nicotinamide adenine dinucleotide(NAD)and nicotinamide adenine dinucleotide phosphate(NADP),which is involved in various physiological and biochemical reactions in the body.Numerous studies have shown that niacin has important effects on growth,digestion and absorption,antioxidant capacity and lipid metabolism in aquatic animals.However,there is a lack of relevant studies in Eriocheir sinensis.Therefore,in this study,the optimal niacin requirement of E.sinensis was investigated and the effect of niacin-fat interaction on the growth,immunity and metabolism of female crab was investigated to provide reference for E.sinensis compound feed development and healthy farming.1.Study on dietary niacin requirements of juvenile Eriocheir sinensisTo determine the optimum requirement of niacin for juvenile E.sinensis,the effects of dietary niacin on the growth performance,intestinal histomorphology and antioxidant capacity were investigated in the present study.The experiment was conducted in the greenhouse recirculating water system of Yangzhou University.360 crabs(initial average weight:1.14±0.04 g)were randomly divided into 6 groups with 3 replicates in each group and 20 crabs in each replicate.Crabs were fed with the control diet(0.89 mg/kg(G1))or niacin-supplemented diets(170.54 mg/kg(G2),347.05 mg/kg(G3),587.59 mg/kg(G4),784.85 mg/kg(G5)and 1248.86 mg/kg(G6))for 12 weeks.The results showed that appropriate dietary niacin(above 347.05 mg/kg)significantly increased the weight gain rate(WGR)and specific growth rate(SGR)(P<0.05),but did not affect the survival rate(SR),feed conversion ratio(FCR),daily feeding rate(DFR)and molting frequency(MF)of crabs(P>0.05).The niacin content in the hepatopancreas of crabs in G1 and G2 were significantly lower than those of the other four groups(P<0.05).Moreover,dietary niacin significantly improved the intestinal histomorphology of crabs by increasing height of folds(HF)and thickness of basement membrane(TM)(P<0.05).Additionally,moderate dietary niacin levels significantly affected the nonspecific immune responses of crabs,by improving the activities of catalase(CAT),glutathione s-transferase(GST),glutathione peroxidase(GSH-Px)and total superoxide dismutase(T-SOD)(P<0.05).Based on the broken-line model analysis of SGR and hepatopancreatic niacin content against dietary niacin level,the dietary niacin requirement of juvenile crabs was suggested to be 420 mg/kg.2.The interaction of dietary niacin and lipid affect the growth,body composition and antioxidative capacity of female Eriocheir sinensisBased on the optimum niacin requirement of E.sinensis,this experiment aimed to determine the effect of interaction between niacin and lipid on growth performance,body composition,digestive enzyme activity and antioxidant capacity of female crabs.The experiment was conducted in the greenhouse recirculating water system of Jiangsu Freshwater and Fisheries Research Institute and lasted for 60 days.162 crabs(initial weight:33.27±0.84 g)were randomly divided into 6 groups,with 3 replicates per group and 9 crabs per replicate,fed with six semi-purified diets.The six groups of crabs were named in order as L6N0(6%fat and 0 mg/kg niacin),L6N400(6%fat and 400 mg/kg niacin),L6N800(6%fat and 800 mg/kg niacin),L12N0(12%fat and 0 mg/kg niacin),L12N400(12%fat and 400 mg/kg niacin)and L12N800(12%fat and 800 mg/kg niacin).The results showed that niacin had no significant effect on the survival rate,growth performance and morphological indicators of female crabs(P>0.05).However,niacin alleviated the reduction of ovarian crude protein caused by high-fat diet(P<0.05).In addition,niacin had no significant effect on the crude components of crab muscle and hepatopancreas(P>0.05).In the absence of niacin,high-fat diet reduced the niacin content in crab hepatopancreas(P<0.05).Niacin had no significant effect on amylase and trypsin(P>0.05),but moderate niacin could increase lipase activity(P<0.05).Excessive intake of niacin reduced the antioxidant capacity of crabs on a low-fat diet,but niacin alleviated oxidative stress caused by high-fat diet(P<0.05).This experiment showed that the diet with 6%fat and 400 mg/kg niacin had advantages in the growth and fattening of female crabs and did not significantly reduce the antioxidant capacity,allowing crabs to maintain a balance between growth performance and immune performance.3.The interaction of dietary niacin and lipid affect the fat deposition and fat metabolism in female Eriocheir sinensisIn this experiment,based on the previous studies,we evaluated the effect of interaction between niacin and fat on fat deposition and lipid metabolism in female E.sinensis.The experiment was conducted in the greenhouse recirculating water system of Jiangsu Freshwater and Fisheries Research Institute and lasted for 60 days.162 crabs(initial weight:33.27±0.84 g)were randomly divided into 6 groups,with 3 replicates per group and 9 crabs per replicate,and fed six semi-purified diets.These diets included L6N0(6%fat and 0 mg/kg niacin),L6N400(6%fat and 400 mg/kg niacin),L6N800(6%fat and 800 mg/kg niacin),L12N0(12%fat and 0 mg/kg niacin),L12N400(12%fat and 400 mg/kg niacin),and L12N800(12%fat and 800 mg/kg niacin).The results showed that excessive niacin significantly reduced the content of TG and T-CHOL in the hepatopancreas of crabs(P<0.05),but had no significant effect on HDL-C and LDL-C(P>0.05).The increase in dietary niacin content significantly increased serum T-CHOL content and decreased LDL-C content(P<0.05).In addition,niacin had no significant effect on the fatty acid composition of muscle,ovary,and hepatopancreas(P>0.05).In terms of gene expression related to lipid metabolism,niacin upregulated the expression of genes related to fat synthesis(srebp-1,fas,dgat-1,Δ9-fad)as well as genes related to fat breakdown(cpt-1a,cpt-1b,cpt-2)(P<0.05).In addition,it also promoted the expression of genes related to fatty acid absorption(fabp-3,fabp-9,fabp-10)and lipid transport(mttp)(P<0.05).These results indicated that niacin can promote lipid synthesis and catabolism in female crabs.However,it is worth noting that the crude fat content of the hepatopancreas and muscle of crabs in the niacin-added group was higher than that in the non-niacin-added group,indicating that niacin may be more advantageous in promoting lipid synthesis in female crabs.