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Probiotics have been documented to promote growth, immunity, and disease resistance in farmed fish. In the present study, we aimed to evaluate single or conjoint effects of some lactic acid bacteria (LAB), namely, Lactococcus lactis, Lactobacillus rhamnosus, and Enterococcus faecalis on the growth performance, immune response, and disease resistance of Carassius auratus. Fish were fed a basal diet supplemented with L. lactis (group B), L. rhamnosus (group C), E. faecalis (group D), L. lactis + L. rhamnosus (group E), L. rhamnosus + E. faecalis (group F), L. lactis + E. faecalis (group G), and L. lactis + L. rhamnosus + E. faecalis (group H) at 5.0 × 108 CFU/g diet for 34 days. After feeding, the final body weight (FBW), weight gain (WG), specific growth rate (SGR), and survival had significantly increased (p < 0.05) for group E. The results indicated that single or conjoint administration of LAB induced high levels of IgM, LZM, AKP, and SOD activity in serum, which may effectively induce humoral immunity, and group E induced even higher levels. At the same time, when compared to the basal diet (group A), the results of qPCR showed that probiotic administration significantly upregulated (p < 0.05) the expression of IL-10, IL-1β, TNF-α, and IFN-γ in the spleen, kidney, liver, and intestine of C. auratus. After challenge with the Aeromonas hydrophila, the survival rates in all probiotic-fed groups were significantly higher (p < 0.05) than those of group A, and the relative protection rates of groups B, C, D, E, F, G, and H were 27%, 30.7%, 40.94%, 42.32%, 39.38%, 33.61%, and 37.5%, respectively. Our data indicated that probiotics could promote growth, enhance immune indicators, and enhance immune capacity. In summary, combined administration of probiotics had a better effect on C. auratus. This experiment could provide a reference for the optimal combination of probiotic additives for aquatic animals. [ABSTRACT FROM AUTHOR]

The study was aimed at investigating the effects of Bacillus velezensis LSG2-5 isolated from host's intestinal tract on growth performance, immune response, antioxidant capacity, and disease resistance of Amur minnow (Rhynchocypris lagowskii Dybowski). 535 fish were divided into 5 groups with 3 replicates per group. Diets containing different doses (0, 106, 107, 108, and 109 CFU/g, respectively) of B. velezensis LSG2-5 were used to feed fish (9.95 ± 0.05 g) for 56 days. Results showed that compared with control, weight gain rate and specific growth rate of fish were significantly increased by dietary 107-109 CFU/g B. velezensis (p <.05). While for the feed conversion ratio, all treatment groups were significantly decreased (p <.05). In serum, the contents of lysozyme and immunoglobulin M were significantly increased by dietary 106-109 CFU/g B. velezensis (p <.05); the activities of component 3, component 4, and alkaline phosphatase were significantly increased by dietary 108 CFU/g B. velezensis (p <.05). The activities of catalase, glutathione peroxidase, total antioxidant capacity, and superoxide dismutase in hepatopancreas were significantly increased by dietary 108-109 CFU/g B. velezensis (p <.05). The activities of catalase, glutathione, glutathione peroxidase, total antioxidant capacity, and superoxide dismutase in the intestinal tract of 108 CFU/g group were significantly increased (p <.05). However, malondialdehyde levels in the hepatopancreas and intestines were significantly decreased by dietary 107-108 CFU/g B. velezensis (p <.05). Dietary 107-109 CFU/g B. velezensis significantly upregulated catalase, glutathione peroxidase, and copper/zinc superoxide dismutase mRNA levels (p <.05). The levels of transforming growth factor β and interleukin-10 mRNA in the hepatopancreas of fish fed with B. velezensis of 108 CFU/g were significantly increased (p <.05), and these in the intestinal tract of 106-109 CFU/g groups were upregulated (p <.05). Feeding dietary 107-108 CFU/g B. velezensis significantly downregulated interleukin-8, interleukin-1β, and tumour necrosis factor α mRNA levels in hepatopancreas and intestines (p <.05). After 56 days of feeding, 225 fish (23.20 ± 0.59 g) were challenged with Aeromonas hydrophila (108 CFU/g), and survival rates were recorded for the next 14 days. Meanwhile, the serum immune parameters of fish were determined. Results showed that compared with control, the survival rates of the treatment groups were significantly increased (p <.05). Lysozyme, component 3, component 4, immunoglobulin M, acid phosphatase, and alkaline phosphatase levels in serum by dietary106-109 CFU/g B. velezensis showed significant promoting effects (p <.05). In conclusion, dietary 107-109 CFU/g B. velezensis boosts the growth, immunity, antioxidant capacity, and against A. hydrophila infection of Amur minnow. Regression analysis suggested that the optimal dose of B. velezensis LSG2-5 in the Amur minnow diet was 5.00 × 10 8 CFU/g. [ABSTRACT FROM AUTHOR]

To evaluate the effects on biochemicals, antioxidants, immune responses and disease resistance of the snakehead fish, following exposure to deltamethrin at 0.061, 0.121, 0.242, 0.485 and 0.970 μg/L. After 28 d, the biochemical, the levels of antioxidant enzymes and immune enzymes in liver, spleen, kidney and intestine were negatively related to the concentrations of deltamethrin exposure. Likewise, the survival rates of the fish after 7 d challenge with Aeromonas veronii were negatively related. The levels of IL-1β, IL-8, TNF-α, Hsp70 and malondialdehyde in liver, spleen, kidney and intestine were positively connected to the concentrations of deltamethrin exposure. Results demonstrated that environmentally relevant concentrations (0.121, 0.242, 0.485 and 0.970 μg/L) inhibited the biochemicals, antioxidants and immune responses and disease resistance of snakehead fish. ga1 • Deltamethrin exposure reduce the hepatopancreas function in C. argus. • Deltamethrin exposure caused tremendous oxidative damage of C. argus. • Deltamethrin exposure significantly suppressed the immune responses of C. argus. • Deltamethrin exposure caused a decrease in resistance to pathogen infection. [ABSTRACT FROM AUTHOR]

The study was the first time to explore the positive effects of α-LA on growth performance, antioxidant capability, immunity, and disease resistance of northern snakehead (Channa argus). Five hundred and forty northern snakehead fish (initial body weight: 8.74 ± 0.12 g (mean ± SE)) were randomly allocated into six groups with three replicates each. Six diets supplemented with α-LA at doses of 0 (CON), 300 (LA300), 600 (LA600), 900 (LA900), 1200 (LA1200), and 1500 (LA1500) mg/kg were fed to northern snakehead for 8 weeks. The results demonstrated that, when compared with the control group, optimal dietary α-LA increased the weight gain (WG), protein efficiency ratio (PER), and specific growth rate (SGR) and reduced the feed conversion ratio (FCR) of the fish (P < 0.05). Also, optimal dietary α-LA enhanced the immune-related parameters and antioxidant enzyme parameters levels in the head kidney, spleen, and liver of northern snakehead (P < 0.05). Dietary α-LA upregulated the mRNA expression levels of anti-inflammatory cytokines (il10 and tgfβ) and antioxidant related genes (gst , gsh-px , gr and Cu/Zn sod), down-regulated the pro-inflammatory cytokines (il1β , il8 , il12 and tnfα) mRNA levels in the liver, spleen and head kidney of the northern snakehead (P < 0.05). The above results demonstrated that optimal dietary α-LA showed enhancement effects on the growth, antioxidant and anti-inflammatory capability, and immune response of northern snakehead. The survival rates in all α-LA treatments were significantly raised after the challenge with Aeromonas veronii (P < 0.05). Based on the quadratic regression analysis of WG, GSH-Px, LYS, and il1β , the optimal dietary α-LA levels were estimated to be 737.0, 775.0, 890.0, and 916.7 mg/kg, respectively. Considering the overall responses in growth performance, antioxidant status, immune response, and inflammatory factors, the recommended dose of α‐LA in the diet of fish is 737.0–916.7 mg/kg. • Optimum dietary α-lipoic acid improved growth, antioxidant and immune function of Channa argus. • Optimum dietary α-lipoic acid could enhance the disease resistance of Channa argus. • The recommended dose of α‐LA in the diet of Channa argus is 737–916.7 mg/kg. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the effect of Bacillus amyloliquefaciens LSG2-8 on the growth performance, immune function, antioxidant capacity, and disease resistance of Rhynchocypris lagowskii. Fish were fed with the feed containing five levels such as 0, 1.0 × 106, 1.0 × 107, 1.0 × 108, and 1.0 × 109 CFU/g of the B. amyloliquefaciens LSG2-8 for 56 days. After 56 days of feeding, twenty four fish were randomly selected to test various growth, immune and antioxidant parameters. Ten fish were challenged with Aeromonas hydrophila for 14 days; the mortality rate was recorded 14 days after infection. The results showed that B. amyloliquefaciens LSG2-8 could significantly increase the growth parameters of R. lagowskii's, such as final body weight, weight gain rate, specific growth rate, and feed efficiency (p < 0.05). Further examination revealed the activity of antioxidant enzymes, Nrf-2 mRNA, and Keap-1 mRNA gene expression in the intestine and liver, and the serum immune index of R. lagowskii in the 1.0 × 108 CFU/g were all significantly higher compared to the other groups. Furthermore, fish fed a diet supplemented with B. amyloliquefaciens LSG2-8 had a significantly lower (p < 0.05) post-challenge mortality rate than the control fish. In summary, the research results showed that B. amyloliquefaciens LSG2-8 could improve the growth performance, immune function, antioxidant capacity, and disease resistance of R. lagowskii and be used in aquaculture. • This study was the first to study the effect of fish-derived Bacillus amyloliquefaciens LSG2-8 on the growth, immune function, antioxidant capacity and disease resistance of Rhynchocypris lagowskii. • The results show that adding a certain concentration of Bacillus amyloliquefaciens LSG2-8 to the diet of Rhynchocypris lagowskii can improve the growth, immune function, antioxidant capacity and disease resistance of Rhynchocypris lagowskii. • This study provides basic data for aquatic microecological preparations. [ABSTRACT FROM AUTHOR]

Lactic acid bacteria (LAB) has been documented to promoting growth, enhancing immunity and disease resistance. In this study, we aimed to evaluate the single or conjoint effects of Lactococcus lactis L19 (Genbank: MT102745.1) and Enterococcus faecalis W24 (Genbank: MT102746.1) isolated from the intestine of Channa argus (C. argus) on growth performance, immune response and disease resistance of C. argus. A total of 720 apparently healthy C. argus (9.50 ± 0.03 g) were randomly divided into four equal groups. Fish were fed with a basal diet (CK) supplemented with L. lactis (L19), E. faecalis (W24), and L. lactis L19 + E. faecalis W24 (L + W) at 1.0 × 108 cfu/g basal diet for 56 days. After feeding, the final body weight (FBW), weight gain (WG), feed efficiency ratio (FER), specific growth rate (SGR) and protein efficiency ratio (PER) had significantly increased (p < 0.05), especially with L19. The results indicated that single or conjoint administration of LAB as potential probiotics can induce high levels of IgM, ACP, AKP, LZM, C3 and C4 activity in serum, which may effectively induce humoral immunity, and L19 induce even higher levels. Meanwhile, when compared to CK group, the results of qPCR showed that LAB administration significantly up-regulated (p < 0.05) the expression of IL-1β, IL-6, IL-10, TNF-α, IFN-γ, HSP70, HSP90, TGF-β in the spleen, head kidney, gill, liver and intestine of C. ar gus. After challenge with Aeromonas veronii , the survival rates in all LAB-fed groups were significantly higher (p < 0.05) than that of the CK group, and the L19 group showed the highest (63.3%) disease resistance. Our data indicated that L. lactis L19 and E. faecalis W24, as a feed additive at 1.0 × 108 cfu/g feed, could promote growth performance, enhance immune response and disease resistance of C. argus , with greatest effects in fish fed L. lactis L19 for 56 days. Hence, these LAB additives could be used as promising probiotics for C. argus. L19 was more effective than W24 or the mixture of the two for promoting growth performance, enhancing immune response and disease resistance of C. argus. • Diet supplemented with single or conjoint Lactococcus lactis L19 and Enterococcus faecalis W24 enhanced the growth, humoral immunity, regulated immune-related genes expression and disease resistance against Aeromonas veronii of Channa argus. • Lactococcus lactis L19 was more effective protection than Enterococcus faecalis W24 or the mixture of the two for promoting growth performance, enhancing immune response and disease resistance of Channa argus. [ABSTRACT FROM AUTHOR]

In the present study, we constructed two recombinant Lactobacillus casei (L. casei) Lc-pPG-1-AcrV (surface-displayed) and Lc-pPG-2-AcrV (secretory) constitutively expressing AcrV protein of Aeromonas veronii (A. veronii). Expression of recombinant AcrV protein was verified by western blot and immunofluorescence technique. Compared with PBS group, the final weight (FW), weight gain (WG) and specific growth rate (SGR) of fish fed Lc-pPG-1-AcrV, Lc-pPG-2-AcrV and Lc-pPG diets after 56 days observed significantly increase (p < 0.05), while the feed conversion ratio (FCR) showed a significantly decrease (p < 0.05). The recombinant L. casei strains were orally administrated to crucian carp, and significant increased (p < 0.05) the immunoglobulin M (IgM), elevated the acid phosphatase (ACP), alkaline phosphatase (AKP), lysozyme (LZM) and superoxide dismutase (SOD) activity in serum. Moreover, leukocytes phagocytosis percentage and index of the recombinant L. casei were both enhanced. The results demonstrated that the recombinant L. casei could elicit systemic immune responses and increase the serum immunological index. The Interleukin-10 (IL-10), Interleukin-1β (IL-1β), interferon-γ (IFN-γ) and Tumor Necrosis Factor-α (TNF-α) levels in liver, spleen, kidney and intestine have up regulated significantly in tissues (p < 0.05), suggesting that the recombinant L. casei has the ability to induce expression of cytokines and enhance the innate immune response. Higher survival rates were exhibited that crucian carp immunized with Lc-pPG-1-AcrV (67.5%) and Lc-pPG-2-AcrV (52.5%) after challenge with A. veronii. In conclusion, these two recombinant L. casei vaccine were effective in improving crucian carp growth, immunity response and disease resistance. The recombinant L. casei strains may be a promising candidate for the development of an oral vaccine against A. veronii. • Two recombinant L. casei expressing AcrV of A. veronii were constructed. • Recombinant L. casei enhanced the growth and activity of ACP, AKP, LZM and SOD and level of IgM and leukocytes phagocytosis in serum. • Recombinant L. casei enhanced the disease resistance and expression level of IL-10, IL-β, IFN-γ and TNF-α in liver, spleen, kidney and intestine of crucian carp fish and disease resistance against A. veronii. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of Bacillus aryabhattai (LSG3-7) and Bacillus mojavensis (LSG3-8) on growth performance, antioxidant capacity, and immune response in Rhynchocypris lagowskii (Dybowski, 1869), at the trial and challenge periods. A 630 healthy fish (10.76 ± 0.05) were randomly divided into six groups: control group (D1) was fed the basal diet, D2 and D3 were supplemented with LSG 3–7 and LSG3-8 (1 × 108 CFU/g) for both of them, whereas D4 was supplemented with a mixture of both bacteria (0.5 × 108 CFU/g each), and D5 was supplemented with LSG3-7 0.75 × 108 CFU/g + LSG3-8 0.25 × 108 CFU/g, and D6 supplemented with LSG3-7 0.25 × 108 CFU/g + LSG3-8 0.75 × 108 CFU/g. After the trial, Aeromonas hydrophila was used in a challenge test for 14 days. Treatments showed significant differences (p < 0.05) in growth performance and antioxidant capacity (CAT, CuZn-SOD, GPX) in the liver and intestine compared to the control. The antioxidant-related genes CAT, CuZn-SOD, GPX, and Nrf2 in the liver and intestine showed upregulation compared with the control group. Serum IgM, LZM, C3, C4, and AKP showed a favorable superiority (p < 0.05) in treatments (D2 – D6) at the trial and challenge test compared to controls. In parallel, immune-related genes (IgM, NF-κB, TLR-1, TLR-2, and MyD88) showed an up-regulated level (p < 0.05) in treatments (D2 – D6) compared to the control. In addition, pro-inflammatory cytokines (IL-1, TNF-α) showed a downregulated level in treatments (D2 – D6). After the challenge test, the immune-related genes in the liver and muscle showed an up-regulated level in treatments compared to the controls. The survival rate showed a significant increase (p < 0.05) in the treatment groups (D2 – D6) compared to the control. Overall, individuals and the bacterial mixture of B. aryabhattai and B. mojavensis could improve the growth performance, antioxidant capacity, immune capacity, and survival rate of R. lagowski i and prevent side effects of A. hydrophila. However, B. mojavensis showed a slight improvement compared to B. aryabhattai without a significant difference between them. • Diets supplemented with B. aryabhattai and B. mojavensis improved the growth performance of R. lagowskii. • B. aryabhattai and B. mojavensis enhanced the antioxidant activity, and immunity R. lagowskii. • These strains increased survival and protected fish from A. hydrophila. [ABSTRACT FROM AUTHOR]