Effect of phosphorus on growth performance, intestinal tight junctions, Nrf2 signaling pathway and immune response of juvenile mirror carp (Cyprinus carpio) fed different α-ketoglutarate levels

Addition of α-ketoglutaric acid (AKG) reduces deamination in Chinese perch (Siniperca chuatsi) fed with fermented soybean meal as a substitute for fishmeal

To alleviate amino acid imbalances in fermented soybean meal as a replacement for fishmeal feeds, this study evaluated the effects of adding lysine (Lys), methionine (Met), and α-ketoglutaric acid (AKG) to fermented soybean meals for Chinese perch. Chinese perch (34 ± 3 g) were fed five diets for 66 days (fishmeal as the protein source of the basal diet [FM]; fermented soybean meal as a substitute for 30% fishmeal in the soybean meal diet [FSM]; addition of crystalline Lys and Met [AA]; addition of α-ketoglutaric acid [AKG]; and simultaneous addition of crystalline Lys, Met, and AKG [BA] to the soybean meal diet). At the end of the feeding trial, the FSM group had the highest feeding rate and the lowest weight gain rate among all the groups. The FM group had the highest protein retention and the lowest feed efficiency among the groups. The mRNA transcription level of genes related to the AMP-activating protein (AMPK) signaling pathway and amino acid response (AAR) signaling pathway (lkb1, atf4, and gcn2) were highest in the AA group (P < 0.05) but lower in the AKG and BA groups. In the AKG group, the mRNA transcription level of the gluconeogenesis pathway-related gene (pepck and g6pase) was significantly higher than that in the other four groups, but the mRNA transcription level of genes related to amino acid catabolism (gdh and ampd) was lower. Among all the groups, the FSM group had the lowest mRNA transcription level of genes associated with the mammalian target of rapamycin (mTOR) signaling pathway (mtor and s6k). These findings imply that the feeding rate of Chinese perch in the fermented soybean meal group was the highest, but the protein retention was the lowest, while the addition of Lys, Met, and AKG improved protein retention. In conclusion, the addition of AKG to fermented soybean meal as a fishmeal substitute reduced amino acid deamination, enhanced gluconeogenesis, and increased protein deposition, which contributed to the growth of Chinese perch, alleviated amino acid imbalances, and improved the feed utilization of Chinese perch.

Dietary α-ketoglutarate alleviates glycinin and β-conglycinin induced damage in the intestine of mirror carp (Cyprinus carpio)

This study investigated the glycinin and β-conglycinin induced intestinal damage and α-ketoglutarate alleviating the damage of glycinin and β-conglycinin in intestine. Carp were randomly divided into six dietary groups: containing fish meal (FM) as the protein source, soybean meal (SM), glycinin (FMG), β-conglycinin (FMc), glycinin+1.0% α-ketoglutarate (AKG) (FMGA), β-conglycinin+1.0% AKG (FMcA). The intestines were collected on 7^th, and the hepatopancreas and intestines were collected on 56^th. Fish treated with SM and FMc displayed reduced weight gain, specific growth rate, and protein efficiency. On 56^th day, Fish fed on SM, FMG and FMc presented lower superoxide dismutase (SOD) activities. FMGA and FMcA had higher SOD activity than those fed on the FMG and FMc, respectively. In intestine, fish fed on the SM diets collected on 7^th presented upregulated the expression of transforming growth factor beta (TGFβ1), AMP-activated protein kinase beta (AMPKβ), AMPKγ, and acetyl-CoA carboxylase (ACC). Fish fed FMG presented upregulated expression of tumor necrosis factor alpha (TNF-α), caspase9, and AMPKγ, while downregulated the expression of claudin7 and AMPKα. FMc group presented upregulated expression of TGFβ1, caspase3, caspase8, and ACC. Fish fed FMGA showed upregulated expression of TGFβ1, claudin3c, claudin7, while downregulating the expression of TNF-α and AMPKγ when compared to fish fed FMG diet. FMcA upregulated the expression of TGFβ1, claudin3c than fed on the FMc. In intestine, the villus height and mucosal thickness of the proximal intestine (PI) and the distal intestine (DI) were decreased and crypt depth of the PI and mid intestine (MI) were increased in SM, FMG and FMc. In addition, fish fed on SM, FMG and FMc presented lower citrate synthase (CS), isocitrate dehydrogenase (ICD), α-ketoglutarate dehydrogenase complex (α-KGDHC) Na⁺/K⁺-ATPase activity in DI. FMGA had higher CS, ICD, α-KGDHC, and Na⁺/K⁺-ATPase activity in PI and MI than those fed on the FMG. FMcA had higher Na⁺/K⁺-ATPase activity in MI. In conclusion, dietary soybean meal destroys the intestine's health, the adverse effects are related to the presence of β-conglycinin and glycinin, especially glycinin. AKG may regulate intestinal energy via tricarboxylic acid cycle, thereby alleviating the damage intestinal morphology caused by the dietary soybean antigen proteins.

Dietary supplementation with Weissella cibaria C-10 and Bacillus amyloliquefaciens T-5 enhance immunity against Aeromonas veronii infection in crucian carp (Carassiu auratus)

With the aim to discover novel lactic acid bacteria and Bacillus strains from fish as potential probiotics to replace antibiotics in aquaculture, the present study was conducted to isolate lactic acid bacteria and Bacillus from intestinal tract of healthy crucian carp (Carassiu auratus) and largemouth bass (Micropterus salmoides) and evaluate their resistance against Aeromonas veronii. Based on the evaluation of antibacterial activity and tolerance test, one strain of lactic acid bacteria (Weissella cibaria C-10) and one strain of Bacillus (Bacillus amyloliquefaciens T-5) with strong environmental stability were screened out. The safety evaluation showed that these two strains were non-toxic to crucian carp and were sensitive to most antibiotics. In vivo study, the crucian carps were fed a basal diet supplemented with W. cibaria C-10 (C-10), B. amyloliquefaciens T-5 (T-5) and W. cibaria C-10 + B. amyloliquefaciens T-5 (C-10+T-5), respectively, for 5 weeks. Then, various immune parameters were measured at 35 days of post-feeding. Results showed both probiotics could improve the activities of related immune enzymes, immune factors and non-specific immune antibodies in blood and organs (gill, gut, kidney, liver, and spleen) of crucian carp in varying degrees. Moreover, after 7 days of challenge experiment, the survival rates after challenged with A. veronii of W. cibaria C-10 (C-10), B. amyloliquefaciens T-5 (T-5) and W. cibaria C-10 + B. amyloliquefaciens T-5 (C-10+T-5) supplemented groups to the crucian carps were 20%, 33% and 22%, respectively. Overall, W. cibaria C-10 and B. amyloliquefaciens T-5 could be considered to be developed into microecological preparations for the alternatives of antibiotics in aquaculture.