Effects Of Dietary Yeast Culture Supplementation On The Growth,Immunity,and Disease-Resistant Against Vibrio Harveyi In Litopenaeus Vannamei And Epinephelus Fuscoguttatus♀×E.Lanceolatu♂

The major challenge face by hybrid grouper and Pacific shrimp farming are bacteria diseases.The used of antibiotics to prevent and control pathogenic microorganisms has been associated with problems such as development and bioaccumulation of antibiotic-resistant pathogens.Currently,supplementing functional feed additives in the diet for aquatic animals has the benefits of stimulating the growth,immune responses,and disease resistance against Vibrio harveyi infection.Therefore,in this present study,the effectiveness of two difference yeast culture protein(50% and 55% crude protein)was evaluated to know their contribution in enhancing the health and growth of both Litopenaeus vannamei and Epinephelus fuscoguttatus♀×E.lanceolatu♂.1.The first experiment was evaluated on the effects of different levels of yeast culture supplementation: C0(0%),A1(1%),and A2(2%),B1(1%)and B2(2%)on the growth,feed conversion ratio,body composition,intestinal morphology,microflora,immune response,and resistance to Vibrio harveyi infection on Pacific white shrimp.The two groups(yeast culture group and the control group)undergone 56 days of feeding trials,the results obtained indicated that the yeast culture group had significant improvement(p < 0.05)with respect to the following;final weight,weight gain rate,specific growth rate,survival rate,and low feed conversion ratio.Serums total protein,superoxide dismutase,catalase,alkaline phosphatase,acid phosphatase,lysozyme,and phenoloxidase in shrimps fed diet of B2(2%)were significantly higher(p < 0.05).There was decreased in serum cholesterol,triglyceride;however,aspartate aminotransferase and alanine aminotransferase significantly decreased(p< 0.05)in the B2(2%)diet group.Proteobacteria,Bacteroidetes,Actinobacteria,and Firmicutes were the core phylum bacteria that were found in the intestines of the shrimp.At the genus level,opportunistic pathogenic bacteria,Vibrio was significantly decreased(P<.05)while beneficial bacteria Pseudoalteromonas was increased in the B2(2%)group.Intestinal villus height and width in shrimps fed yeast culture diets were significantly improved than the control diet(P <.05).Yeast culture groups challenged test showed(P<.05)significantly improved shrimps immune response against V.harveyi infections with B2(2%)recording the highest percentage survival rate.This study demonstrated that supplementing B2(2%)improves the growth,intestinal microbiota,intestinal morphology,and immune response against V.harveyi infections in Pacific white shrimp.2.The second experiment was carried out to determined dietary yeast culture supplementation effects at different inclusion levels CO(0%),L1(2%),L2(4%),N1(2%)and N2(4%).At the end of 56 days feeding trial,the results indicated that survival rate(SR),weight gain rate(WGR),and specific growth rate(SGR)of hybrid grouper were significantly high in N1(2%)and N2(4%)group than the control group(P < 0.05).The data on carcass analysis showed significant improved crude protein,and ash in N2(4%)treated group(P < 0.05),whereas significant increase crude lipid was observed in N1(2%)treated group(P < 0.05).Of the phylum level,the relative abundance of Actinobacteria and Bacteroidetes were significantly higher N2(4%)groups.At the genus level,the relative abundance of Sphingomonas,Lactobacillus,and Bifidobacteria was significantly higher in the yeast culture treatment groups.Furthermore,levels of(SOD),catalase(CAT),total protein(TP),lysozyme(LYZ),alkaline phosphatase(AKP),acid phosphatase(ACP),and immunoglobulin(Ig M)(P < 0.05)in fish serum were significantly higher in yeast culture supplementation groups(P < 0.05).Contrary to the control,a significant decrease tendency of serum cholesterol(CHO),triglyceride(TG),aspartate aminotransferase(AST),alanine aminotransferase(ALT),malondialdehyde(MDA)and glucose(GLU)in fed yeast culture supplementations group.Hybrid grouper fed N1(2%)and N2(4%)groups significantly improved intestinal villus height and width(P > 0.05).Lastly,the protection against V.harveyi challenge in hybrid grouper was enhanced in the yeast culture treated group,while N2(4%)experienced highest relative percentage survival of 80.0 %,followed by N1(2%)group with 64.6 %,L2(4%)group with 50.0 %,L1(2 %)growth with 44.6 %,and CO(0 %)group with 26.4 %.Taken the results into consideration,it could be concluded that yeast culture groups had the benefit to be used as feed supplements to enhance hybrid grouper farming.Particularly,N2(4%)group is suggested as the best to improve growth and the immunity of hybrid grouper.