Effects Of Alginate Oligosaccharide On Growth,Intestinal Health,Immunity And Disease Resistance Of Scophthalmus Maximus And Litopenaeus Vannamei

Scophthalmus maximus and Litopenaeus vannamei are important mariculture animals in our country.However,the outbreak of bacterial diseases caused great losses in the breeding process.Therefore,in order to improve the disease resistance of turbot and Litopenaeus vannamei,different concentrations of alginate oligosaccharides(AOS)were added to the diets of turbot and Litopenaeus vannamei,in order to investigate the effects of Alginate oligosaccharides(AOS)on the disease resistance,immunity and intestinal health of turbot and Litopenaeus vannamei,and to provide theoretical guidance for their use in production.1.Effects of AOS on growth,intestinal health,immunity,and disease resistance of Scophthalmus maximus.A control diet(TAOS0)was supplemented with 0.07%(TAOS0.07),0.6%(TAOS0.6)and 1.2%(TAOS1.2)Alginate oligosaccharides,respectively.Turbots with initial body weight of 230±5 g were fed with these four diets,and the experiment lasted for 8 weeks.After 8 weeks,AOS significantly improved the growth performance of turbot,and the survival rate,weight gain rate and feed efficiency were significantly increased compared with control group(P<0.05).In the challenge experiment,the cumulative mortality of the treatment groups supplemented with 0.07%and 0.6%AOS was significantly decreased compared with the control group(P<0.05),and the resistance of turbot to Vibrio parahemolyticus infection was significantly improved(P<0.05).In terms of immune-related enzyme activities,AOS significantly increased the activities of liver superoxide dismutase(SOD)and catalase(CAT)and serum lysozyme(LZM),acid phosphatase(ACP)and nitric oxide synthase(NOS).In the intestinal structure and function of turbot,AOS improved the intestinal villus height and intestinal wall thickness,increased the activity of brush membrane enzymes,and promoted intestinal development and function of turbot.AOS changed the intestinal flora structure of turbot,and the number of specific ASVs increased.There were obvious differences among different treatment groups,and the structure of bacterial community changed obviously.The results showed that dietary supplementation of 0.07%-0.6%AOS could improve the growth performance and strengthen the disease resistance of turbot2.Effects of AOS on growth,intestinal health,immunity,and disease resistance of Litopenaeus vannamei.On the basis of a control experimental diet(AOS0),the five diets were supplemented with 0.07%(AOS0.07),0.2%(AOS0.2),0,6%(AOS0.6)and 1.2%(AOS 1.2)Alginate oligosaccharides,respectively,and the five diets were fed with Litopenaeus vannamei with an initial body weight of 2.10±0.07 g.The experiment lasted eight weeks.After 8 weeks,dietary supplementation of AOS significantly increased the resistance to Vibrio parahaemolyticus infection of Litopenaeus vannamei(P<0.05).In terms of immune-related enzyme activities,AOS significantly increased the total antioxidant capacity(T-AOC),superoxide dismutase(SOD)activity and serum nitric oxide synthase(NOS)activity of hepatopancreas of Litopenaeus vannamei(P<0.05);In the expression of immune-related genes,AOS significantly increased the relative expressions of LGBP,Toll,IMD,Pen-3α,proPO,Crustin and HSP70 genes of Litopenopenus vannamei(P<0.05).In the intestinal structure and function of Litopenaeus vannamei,AOS improved the intestinal villus height and intestinal wall thickness,increased the activity of brush membrane enzymes,and promoted the intestinal development and function of Litopenaeus vannamei.In the intestinal flora structure of Litopenaeus vannamei,AOS changed the intestinal flora structure of Litopenaeus vannamei,and the number of specific ASVs decreased.There were significant differences among all treatment groups.The results showed that the disease resistance of Litopenaeus vannamei was enhanced by adding more than 0.07%AOS in the diet.