粪肠球菌后生元对大口黑鲈生长、非特异性免疫、抗氧化和肠道健康的影响OA

Largemouth bass(Micropterus salmoides),as an important characteristic freshwater aquaculture species,is highly favored for its delicate flesh,rapid growth,and absence of intermuscular bones.However,high-density intensive farming has led to frequent disease outbreaks,and the extensive use of antibiotics has resulted in the emergence of antimicrobial resistance and drug residues.Postbiotics,as non-viable microbial components with probiotic functions,have the potential to improve host health,enhance immunity,and protect against pathogens,making them a research hotspot as potential antibiotic alternatives.This study investigated the effects of feeding live Enterococcus faecalis(MSEF22)and its postbiotic components(HK-EF)on the growth,immunity,antioxidant capacity,intestinal barrier integrity,and gut microbiota of M.salmoides.Fish with an initial body weight of(30.78±0.57)g were randomly assigned to three groups:a control group(basal diet+PBS),an MSEF22 group(basal diet+E.faecalis,1×107 CFU/g),and an HK-EF group(basal diet+inactivated E.faecalis,1×107 CFU/g).A 42-day feed-ing trial was conducted.Results showed that both MSEF22 and HK-EF significantly increased the weight gain rate(WGR)and specific growth rate(SGR).Serum biochemical analysis revealed significant increases in alkaline phosphatase(AKP)and acid phosphatase(ACP)levels in fish fed with MSEF22 or HK-EF.Histological examination of intestinal tissues showed more intact and smoother intestinal epithelial villi,along with a significant increase in goblet cell numbers in both treatment groups.Gut microbiota analysis indicated that the Chao1 index of the MSEF22 group differed markedly from the control group.HK-EF supplementation significantly increased the abundance of Cetobacterium,while both MSEF22 and HK-EF significantly reduced the abundance of Mycoplasma,a known pathogen.Moreover,MSEF22 and HK-EF enhanced the interactions of Cetobac-terium with other gut microbes,promoting a stable microbial community,as demonstrated by a co-occurrence network analysis.In conclusion,feeding MSEF22 and HK-EF improved the growth performance,non-specific immune function,and antioxidant capacity of M.salmoides,while enriching beneficial gut bacteria and maintaining intestinal health.These findings suggest that postbiotic metabolites of E.faecalis have promising potential for application in intensive aquaculture.