Oxidative damage caused by overwintering stress is a key bottleneck limiting stable yields in aquatic animals. However, Aurantii fructus immaturus (AFI) has been shown to possess antioxidant and anti-inflammatory properties, making it an important and promising nutritional intervention strategy for alleviating overwintering stress. The present study was conducted to evaluate the impact of AFI on the growth performance, immune response, and intestinal contents of bullfrogs post-overwintering. Bullfrogs (151.07 ± 0.04 g) that had undergone a 1-month hibernation period were selected as the study subjects. Four treatment groups were established: the BCON group (no feeding after overwintering), the control (CON), and CON supplemented with 1000 mg/kg (LAFI) or 5000 mg/kg (HAFI) of AFI. The feeding period lasted 4 weeks. The results showed that dietary AFI supplementation post-overwintering significantly enhanced (P < 0.05) the growth performance of bullfrogs. Notably, the LAFI group displayed superior growth outcomes compared to the HAFI group, which was positively correlated with significant increases in intestinal digestive enzyme activities, villus height, and muscle thickness. AFI enhances gut antioxidant capacity by up-regulating the expression of cybb, cat, gshpx, mgst and sod. Furthermore, it maintained intestinal immune homeostasis by suppressing the TLR/NF-κB signaling pathway, significantly down-regulating the expression of tnfα and il1β mRNA and up-regulating the expression of il10 mRNA (P < 0.05). Additionally, AFI supplementation significantly altered the intestinal microbial community structure, increasing the relative abundance of Weissella and Cetobacterium while decreasing Clostridium (P < 0.05). Correlation analysis confirmed that changes in the dominant gut microbiota were closely associated with improvements in growth, immune function, and antioxidant parameters in bullfrogs. Collectively, these results demonstrate that compared to the CON group, AFI mitigates the adverse effects of overwintering stress on the reduced antioxidant capacity and decline in immune function in bullfrogs by reshaping the microbial community, thereby improving growth performance.

Psoriasis is a chronic inflammatory skin disease with limited safe and effective treatments. Methylparaben, a widely used preservative in cosmetics, pharmaceuticals, and food, is an emerging environmental pollutant linked to immune-related skin disorders, but its role and mechanism in psoriasis remain unclear. This study explored its potential mechanism using network toxicology, molecular docking, molecular dynamics simulation, and eight machine learning algorithms. Methylparaben targets were retrieved from GeneCards and TCMSP, and psoriasis-related targets from CTD and GeneCards. Overlapping targets were screened with Venny 2.1.0. A PPI network was constructed via STRING, and core targets identified using Cytoscape 3.10.2. GO and KEGG enrichment analyses were performed on DAVID. Molecular docking evaluated the binding affinity of methylparaben with key targets. A total of 138 compound-related and 5,592 psoriasis-related targets were identified. Core targets such as INS, HIF1A, and PPARG are involved in regulating immune-inflammatory responses, keratinocyte proliferation and differentiation, and oxidative stress. GO analysis revealed enrichment in xenobiotic metabolism, lipopolysaccharide response, and metal ion binding. KEGG analysis highlighted pathways related to cancer, chemical carcinogenesis from reactive oxygen species, and drug metabolism via cytochrome P450 enzymes. Molecular docking showed stable binding of methylparaben to INS (-4.5 kcal/mol), HIF1A (-5.9 kcal/mol), and PPARG (-5.5 kcal/mol), primarily through hydrogen bonds and hydrophobic interactions. Methylparaben may exert its effects on psoriasis via multi-target and multi-pathway mechanisms, influencing inflammation, oxidative stress, and cellular regulation. These findings provide valuable insight into its toxicological mechanism and potential therapeutic application.

The “torticollis disease” in bullfrogs poses a severe threat to aquaculture, and infection with E. miricola has been identified as a key causative factor. This study aimed to develop targeted prevention and control strategies. Through in vitro antibacterial screening, rosmarinic acid (RosA) was identified to exhibit significant inhibitory activity against E. miricola, with stable activity after heat treatment at 120 °C for 5 min. Animal experiments showed that dietary supplementation with RosA (1 and 4 g/kg) for 8 weeks significantly reduced the morbidity (15%–20%) and mortality (25%–30%) of bullfrogs after E. miricola challenge. Mechanistic studies revealed that RosA intervention significantly suppressed the overactivated inflammatory signaling pathways (e.g., TLR, NF-κB) in the brain tissues of infected bullfrogs, leading to downregulated expression of key genes (tlr5, myd88, nfκb, tnfα, and il1β). Further validation using the frog kidney epithelial cell model demonstrated that RosA (100–200 μM) effectively antagonized E. miricola infection-induced cell apoptosis and the significant upregulation (3–15 fold) of key inflammatory genes (tlr5, myd88, nfκb, tnfα, il1β, and cxcl8). Notably, the combined use of RosA and a MyD88-specific inhibitor produced a synergistic effect, significantly enhancing the inhibitory effect on downstream genes (nfκb, cxcl8, tnfα, and il1β), confirming that the TLR5/MyD88/NF-κB signaling axis is an important pathway for E. miricola-induced inflammation. This study reveals that E. miricola infection is associated with the activation of the TLR5/MyD88/NF-κB pathway in neuroinflammation, and demonstrates that RosA exerts dual antibacterial and anti-inflammatory effects, which include the suppression of this pathway's activation. These findings suggest a potential mechanism for RosA-mediated protection and provide important theoretical support for developing natural compound-based feed additives to control aquatic bacterial diseases.

Soy protein concentrate (SPC) is a potential plant-protein ingredient for aquafeeds, but inadequate lysine availability may limit its nutritional value in formulated diets. This study evaluated the effects of lysine supplementation in SPC-based diets on growth performance, nutrient utilization, physiological responses, and tissue characteristics of hybrid sturgeon (Acipenser baerii ♀ × A. schrenckii ♂). Juveniles with an initial body weight of 8.0g were fed four isonitrogenous and isolipidic diets for 8 weeks: a fish meal (FM)-based control diet and three SPC-based diets supplemented with 0% (L0), 0.25% (L2.5), or 0.50% (L5) lysine. Relative to L0, L2.5 increased final body weight and weight gain rate, whereas feed conversion ratio and protein efficiency ratio did not differ significantly between the two groups. Increasing supplementation to 0.50% provided no additional growth benefit; L5 had poorer FCR and PER than L2.5. Whole-body proximate composition and amino acid profiles were unaffected by dietary treatment. The L5 group exhibited the highest hepatic MDA content and CAT activity, together with altered serum biochemical indices. In the intestine, L2.5 showed higher lipase activity and villus height than L0 and L5, whereas L5 exhibited lower trypsin activity, muscular layer thickness, and goblet cell abundance. Relative to L2.5, L5 also showed lower transcript levels of tight-junction- and immune-defense-related genes and higher expression of the pro-inflammatory genes il-8 and tnf-α. Muscle fiber density was higher in L2.5 than in L0 and L5, whereas L5 showed lower springiness and chewiness than L2.5. Overall, 0.25% supplemental lysine produced the most favorable growth, intestinal, and muscle responses among the SPC-based diets tested. Further dose–response studies are required to establish the dietary lysine requirement of hybrid sturgeon fed SPC-based diets.

Oxidation of dietary fish oil is a persistent challenge in aquaculture because it disrupts redox balance, lipid metabolism and intestinal homeostasis. The oleanolic acid (OA) modulate the oxidative stress and metabolic disturbances in rice field eel (Monopterus albus). In a 56-day feeding trial, a total of 720 rice field eels (initial body weight: 20.00 ± 0.04 g) were randomly allotted to four dietary treatments with three replicates per treatment (60 fish per cage): normal diet (CON), oxidized fish oil (OFO), OFO with 300 mg/kg OA (OA1), and OFO with 1500 mg/kg OA (OA2). Compared with OFO group, OA supplementation increased hepatic T-AOC and CAT activities and reduced lipid peroxidation levels (P < 0.05). OA group exhibit significant up-regulation of antioxidant responses (gpx8, nrf2, sod1), sterol biosynthesis (lss, msmol, and ebp), and autophagy-related (mcl1, lc3b, atg5, and atg7) processes in the liver (P < 0.05). Moreover, OA improved gut microbial composition by increasing the relative abundance of Lactococcus and reducing the abundance of potential dysbiosis-associated taxa, particularly members of Proteobacteria. Serum metabolomic further showed that OA supplementation was associated with changes in lipid-related metabolites, and KEGG enrichment highlighted diterpenoid biosynthesis in OA1 and brassinosteroid biosynthesis were markedly enriched in OA2. These findings suggest that OA potential as a functional additive for mitigating the adverse effects of dietary lipid oxidation in rice field eel.

This study was conducted to investigate the effects of different dietary protein and lipid levels on the growth performance,hepatic antioxidant capacity,and protein-lipid metabolism of juvenile Pelophylax nigromaculatus.A 4×2 factorial design was used,with dietary protein levels set at 38.5%,41%,43.5%,and 46%,and dietary lipid levels of 8%and 10%,resulting in the formulation of 8 experimental diets.Juvenile P.nigromaculatus with an initial body weight of(15.00±0.10)g were fed the diets for 8 weeks.The results indicated that the average weight gain rate(WGR)initially increased and then decreased with increasing dietary protein and lipid levels.The 41P10L group achieved the highest WGR,but no significant difference was observed compared with the 38.5P10L and 41P8L groups(P>0.05).Additio-nally,the 38.5P10L group showed the highest protein efficiency ratio(PER)(P<0.05).Among all groups,the 46%protein group had the highest average contents of serum total cholesterol(TC),high-density lipoprotein cholesterol(HDL-C),albumin(ALB),and urea nitrogen(BUN),while the 43.5%protein group exhibited the highest average contents of serum triglycerides(TG)and low-density lipoprotein cholesterol(LDL-C)—with these respective indices in both groups being significantly higher than those in the 38.5%protein group(P<0.05).The results of oil red O staining indicated that lipid deposition in the liver of P.nigromaculatus was aggravated at the 10%lipid level,particularly under 43.5%and 46%protein levels(P<0.05).The average serum activities of glutamic-pyruvic transaminase(GPT)and glutamic-oxaloacetic transaminase(GOT)in the 46%protein group were significantly higher than those in the 38.5%protein group(P<0.05).Additionally,the average activities of intestinal digestive enzymes,hepatic antioxidant enzymes,and the malondialdehyde(MDA)content increased with the elevation of dietary protein and lipid levels.Regarding gene expression,the relative expression levels of hepatic mtor and s6k in the 46%protein group were signifi-cantly higher than those in the 38.5%protein group(P<0.05),while the hepatic cpt1 expression level in the 10%lipid group was significantly higher than that in the 8%lipid group(P<0.05).In conclusion,although a dietary protein level of 41%supported higher WGR,it resulted in reduced PER.In contrast,dietary protein levels of 43.5%and 46%were more prone to induce aggravated hepatic lipid deposition and hepatic injury.Considering comprehensive factors includ-ing growth performance,protein utilization efficiency,and hepatic health,the optimal dietary protein level for P.nigro-maculatus was determined to be 38.5%,with an optimal dietary lipid level of 10%.

The substitution of fish meal with soybean meal (SBM) in aquafeeds aligns with sustainable development but often leads to depressed feed intake and growth in fish. This study aimed to investigate the mitigating effect of earthworm powder (EP) on these negative impacts in rice field eels (Monopterus albus), focusing on appetite regulation, intestinal health, and gut microbiota. Three isonitrogenous (~41% crude protein) and isolipidic (~6.4% crude lipid) diets (control [CON], high-SBM [SBM], and SBM + 2.5% EP [EP]) were tested in a 56-day trial. Juveniles (initial weight 18.00 ± 0.01 g) were stocked at 40 fish per net (0.5 m × 0.5 m× 0.5 m) and fed to visual satiety once daily. The results indicated that EP improved growth performance through a dual mechanism. Firstly, it was associated with significantly increased feed intake, correlated with the upregulated expression of orexigenic genes (agrp, npy) in the brain, and associated with reduced levels of anorexigenic hormones (Cholecystokinin, Leptin). Secondly, it correlated with enhanced intestinal health, evidenced by improved morphology (villus height, goblet cells), improved digestive enzyme activity, enhanced antioxidant capacity (increased Catalase and Superoxide Dismutase activities), repaired intestinal barrier function (upregulated zo-1, cla-12), and alleviated intestinal inflammation (downregulated tnf-α, il-1β). Furthermore, EP supplementation was associated with a shift in gut microbiota, including the suppression of the potential pathogen g_Clostridium_T and promotion of the beneficial bacterium g_Lactococcus_A, alongside increased concentrations of major short-chain fatty acids (acetate, propionate, and butyrate). These correlative observations suggest that EP may help mitigate the growth-inhibiting effects of SBM in Monopterus albus, offering a potential functional strategy for high-SBM aquafeeds.

High-fat diets are commonly used in crustacean aquaculture to reduce protein costs, but excessive fat intake can impair growth and health. This study investigated whether lysophosphatidylcholine (LPC), an emulsifying additive, is associated with the mitigation of negative effects of high-fat diets in crayfish (Procambarus clarkii). A total of 600 crayfish (4.00g) were randomly divided into four groups with three replicates: control (CK, 6.70% fat), high-fat diet (HFD, 10.21% fat), and HFD supplemented with 38.75mg/kg (LPD) and 82.54mg/kg LPC (HPD) for six weeks. Results showed that crayfish given a high-fat diet presented considerable decreases in final average weight, specific growth rate, and weight gain rate (P < 0.05), coupled with an increase in hepatosomatic index (P < 0.05). Supplementing with LPC helped alleviate hepatopancreas damage induced by high-fat diets, as demonstrated by reduced vacuolization and lower malondialdehyde level, along with decreased aminotransferase activities (P < 0.05). LPC also enhanced antioxidant capacity (increased glutathione, P < 0.05) and suppressed key lipid metabolism enzymes (P < 0.05), indicating reduced hepatic lipid accumulation. Further microbial profiling presented that LPC supplementation co-occurred with a restored microbial balance, characterized by reduced Proteobacteria (Citrobacter, Pseudomonas) and increasing Firmicutes (Tyzzerella), and a predicted suppression of lipopolysaccharide biosynthesis. These findings suggest that dietary LPC effectively counteracts high-fat diet-induced growth decline, hepatopancreas damage, which is associated with restructuring of the gut microbiota and suppression of harmful metabolic pathways. Our results provide a correlative basis and generate the hypothesis that LPC may exert its beneficial effects through microbiota modulation, warranting further mechanistic validation.

This study aimed to evaluate the effects of using red fish meal (PRF, Peruvian red fish meal) and four types of white fish meal (NZWF, New Zealand white fish meal; NPWF, North Pacific white fish meal; RWF, Russian white fish meal; DWF, Danish white fish meal) as dietary protein sources on the growth performance, serum biochemical indices, intestinal histomorphology, antioxidant capacity, immune response, expression of genes related to the physical barrier, and gut microbial community in rice field eel (Monopterus albus), in order to identify the optimal fish meal type. Compared to the PRF group, the white fish meal groups showed significantly increased final mean body weight and condition factor. Serum levels of TG, TC, and BUN decreased significantly, while levels of GLU, IgM, and IgA increased significantly. Histological examination of the intestine revealed increased villus height and goblet cell density in the white fish meal groups. Furthermore, the white fish meal groups upregulated intestinal expression levels of nrf2, sod, cat, gpx1, tgf-β1, zo-1, zo-2, cl-12, cl-15, and occ, and downregulated expression levels of il-1β, il-8, nf-κb, and tlr-3. Gut microbiota analysis revealed that the abundance of Bacteroidota was higher in the white fish meal groups than in the PRF group (>70% vs ∼50%), with significant enrichment of Muribaculaceae and Bacteroides. Network modules 1 and 2 showed strong positive correlations with growth/immune indices. Differential abundance heatmap analysis showed that NPWF and NZWF clustered into a healthy cluster, while PRF formed a separate cluster. White fish meals are superior to red fish meal, with NPWF demonstrating the best overall performance in terms of growth, metabolism, intestinal barrier function, immune regulation, antioxidant capacity, and beneficial bacterial network.

Clostridium butyricum metabolites (CBM) serve as a functional supplement with anti-oxidant and immune-enhancing properties, yet its role in aquatic animals subjected to dietary high plant-derived diets and over-wintering remain understood. The present study evaluated the effect of CBM on anti-oxidative capacities and immunity in grass carp post-overwintering and its resistance of pathogen challenge. Based on our previous investigations, grass carp were fed three diets over 60 days, low cottonseed and rapeseed meal diet (CON), high cottonseed and rapeseed meal diet (CBM0) and CBM-supplemented diet (CBM1), respectively, followed by 4-month overwintering treatment. The findings demonstrated that CBM supplementation maintained liver and gut health of grass carp as evidenced by reduced serum D-lactate level, transaminase activities, decreased hepatocyte vacuolization (P < 0.05). Moreover, liver and intestinal antioxidant properties were enhanced by supplementation with CBM, as demonstrated by the decrease in malondialdehyde content (P < 0.05), and enhancement in superoxide dismutase, catalase, and glutathione peroxidase levels, and up-regulation of mnsod, cat, gsto, and gpx1 levels. Supplementation of CBM suppressed p38mapk, tlr2, myd88, nfkb, and tnf-α, coupled with the increased complement C4, immunoglobulin M, and tgf-β1 and il-15 levels (P < 0.05). Moreover, under Aeromonas hydrophila infection, grass carp ingesting CBM showed markedly decreased mortality compared to CBM0 (P < 0.05). This research demonstrated that overwintering stress markedly increased the incidence of oxidative stress and inflammatory responses in grass carp. CBM can alleviate overwintering inflammation and oxidative damage, and enhance antibacterial capacity.

An 8-week feeding trial was conducted to assess the effects of hydrolyzed feather meal (HFM) as a fish meal replacement on the growth performance, flesh quality, skin color, and intestinal microbiota of yellow catfish (Pelteobagrus fulvidraco). Five isonitrogen (44% crude protein) and isolipidic (8.5% crude lipid) diets were formulated with varying levels of HFM at 0% (FM, control), 2.05% (HFM2), 4.10% (HFM4), 6.15% (HFM6), and 8.20% (HFM8), corresponding to fish meal replacement of 0%, 8.33%, 16.67%, 25%, and 33.33%, respectively. Results indicated that the growth performance declined significantly as HFM inclusion increased. Based on the results of weight gain rate (WGR) and specific growth rate (SGR), the maximal replacement levels of fish meal with HFM for yellow catfish should be 16.67%. Intestinal enzyme activities, including trypsin, lipase, amylase, and Na+-K+-ATPase as well as villus height, muscular thickness, and goblet cells number were significantly enhanced in HFM groups. Fish meal replacement with HFM remarkably reduced serum immune indicators acid phosphatase, immunoglobulin M, Complement 3, and Complement 4 levels and significantly increased serum aspartate aminotransferase, total triglycerides, and cholesterol levels, indicating compromised immune function and liver health. The content of collagen and flavor-enhancing amino acids (glutamic acid [Glu], glycine [Gly], and alanine [Ala]), as well as muscle hardness were distinctly boosted, demonstrated an elevated flesh texture led by dietary HFM inclusion. The abnormal skin coloration induced by pigmentary disorders was observed in high HFM inclusion groups, the black pigmentation on dorsal and yellow pigmentation on the abdomen exhibited a gradual reduction in intensity. The study found that replacing up to 16.67% of fish meal with HFM in yellow catfish diets maintained growth performance and improved meat quality. However, high HFM levels damaged serum immune system and caused liver dysfunction, dyslipidemia, pigmentary disorders, and reshaped intestinal microbial structure.

An 8-week feeding trial was conducted to evaluate the feasibility of substituting soybean meal (SBM) with degossypolized cottonseed protein (DCP) on Hefang bream. Five iso-nitrogenous and iso-lipidic diets were formulated with graded replacement levels of SBM by DCP at 0% (control), 25% (DCP25), 50% (DCP50), 75% (DCP75), and 100% (DCP100). Results showed that DCP could effectively replace up to 50% of dietary SBM in Hefang bream, without adverse influence on survival rate and growth performance. However, the specific growth rate in fish fed diets with DCP replacing 75% and 100% of SBM decreased significantly. Muscle essential amino acid profiles showed marked reductions in isoleucine, leucine, and lysine concentrations in fish fed diets with DCP replacing 75% and 100% of SBM, correlating with suppressed mTOR pathway transcription. The intestinal villi length and the intestinal trypsin activity in fish fed diets with DCP replacing 75% and 100% of SBM were significantly lower than those in the control group. The total antioxidant capacity and catalase activity in fish fed the diet with DCP replacing 100% of SBM were significantly lower than those in the control group. The mRNA expression of hepatic inflammatory cytokines in fish fed the diet with DCP replacing 25% of SBM was the lowest among the groups. In conclusion, these findings suggest that DCP can replace up to 50% of SBM in diets of the Hefang bream without compromising the growth performance. However, excessive dietary DCP (75%-100%) can induce protein utilization impairment, digestive dysfunction, oxidative stress, and hepatic inflammation.

Feed nutrients are crucial in shaping the gut microbial community, especially for complex interactions. While much research focused on the impacts of dietary protein levels, exploration of protein sources remains insufficient. Accordingly, this study specifically investigated the effects of four protein sources [Clostridium autoethanolicum protein (CAP), cottonseed protein concentrate (CPC), Chlorella vulgaris meal (CVP), and Tenebrio molitor meal (TM)] replacing dietary soybean meal on microbial co-occurrence networks and key metabolic taxa. A 56-day feeding trial involved 1500 grass carp (20.00 g) fed five experimental diets, each incorporating one of the experimental protein sources. Results revealed that CPC and CVP diets improved the weight gain and specific growth rate, with the CPC group demonstrating the highest biomass gain and the CVP group exhibiting the best feed conversion ratio. Findings further indicated that SM-free diets enhanced intestinal immunity and barrier function while negatively impacting microbial diversity. Additional profiling revealed that each treatment exhibited distinct abundance profiles and unique species, with Firmicutes, Bacteroidota, and Proteobacteria as the dominant phyla and key genera such as Bacteroides, Erysipelatoclostridium, and Cetobacterium. Stochastic mechanisms drove the community assembly process, and prolonged SM-free diets led to simplified networks with increased generalists and specialists. Functional gene analysis highlighted roles in amino acid, carbohydrate, and lipid metabolism, underscoring the impact of protein sources on aquatic microbial communities and host-microbiome interactions. Overall, the study suggests the potential suitability of several protein sources as soybean meal substitutes, emphasizing the importance of further investigation into optimal inclusion levels for diverse proteins.

A 10-week growth experiment was conducted to evaluate the physiological effects of dietary phosphorus supplementation on red swamp crayfish (Procambarus clarkii) feeding diets with high Clostridium autoethanogenum protein (CAP) levels. Six isonitrogenous and isolipid diets were formulated: The FM diet contained 10% fishmeal, which is equivalent to a dietary phosphorus level of 1.41%, and the CAP, CAPSP1, CAPSP2, and CAPSP3 diets substituted all fishmeal with CAP and supplemented with 0, 2.5%, 3%, and 3.5% Ca(H2PO4)2, respectively (corresponding to dietary phosphorus levels of 0.66%, 1.27%, 1.40%, and 1.52%). A total of 600 crayfish with an initial mean weight of (5.01 ± 0.02) g were selected and randomly assigned to 15 cages for feeding and sampled at the end of the experiment. Results indicate that high-dose CAP replacing fishmeal caused abnormal hepatopancreatic tissue structure in crayfish, exacerbating lipid deposition and oxidative stress. Compared with the CAP group, the specific growth rate (SGR) of crayfish in the CAPSP2 and CAPSP3 groups significantly increased (p < 0.05). The activities of antioxidant enzymes and lipid-degrading enzymes in the hepatopancreas, along with the relative expression of related genes, were significantly enhanced (p < 0.05). Metabolomic analysis demonstrated significant differences in major differential metabolites and metabolic pathways between the CAP group crayfish and the CAPSP2 group (p < 0.05). CAPSP2 group crayfish exhibited a higher content of phosphatidylcholine (PC) and lysophosphatidylcholine (LPC), with significant enrichment in glycerophospholipid metabolism and fatty acid metabolism pathways (p < 0.05). Overall, supplementing dietary phosphorus levels to 1.40-1.52% effectively mitigated growth retardation, oxidative damage, and lipid metabolism disorders induced by high-proportion CAP replacement of fishmeal.

This investigation aimed to examine the impact of nano-selenium as a functional feed supplement on bullfrogs. The experiment selected 630 healthy bullfrogs with the same initial weight (24.25 +/- 0.02 g) from the same batch, randomly divided into 3 groups with three replicates each. Three different selenium containing diets (CON, N0.4, N0.8) were set based on the basic diet (control group) and supplemented with different levels of nano-selenium (0, 0.4, 0.8 mg/kg) for an 8-week continuous feeding experiment. The experimental results showed that dietary nano-selenium supplementation significantly improved average weight gain rate, total weight gain rate and the survival rate of the bullfrog (P < 0.05). Supplementation of nano-selenium effectively improved intestinal structure and enhanced digestive enzyme activity, thereby facilitating the absorption of nutrients. In addition, nano-selenium supplementation alleviated liver impairment in bullfrogs due to dietary challenges, as evidenced by more structurally intact hepatocytes, significantly reduced cell vacuolization, and GOT and GPT activity in the nano-selenium group. Moreover, the serum content of acid phosphatase (ACP) and alkaline phosphatase (AKP) were significantly increased followed nano-selenium addition (P < 0.05), indicating the enhanced host innate immune capacity. Dietary nano-selenium intake boosted the antioxidant capacity and relieved inflammatory response of liver and intestine tissues at enzymatic and transcriptional level. In conclusion, nano-selenium can effectively improve the health condition of bullfrogs, combined with the actual production to evaluate the optimal additive amount of 0.4 mg/Kg.

The impacts of substituting dietary soybean meal (SBM) with yellow mealworm meal (YMM) were investigated during a 56-day feeding trial on growth, antioxidant capacity, immunity, intestinal morphology, and intestinal microbiota of grass carp. A total of 750 grass carp were divided into 5 groups (3 replications per group and 50 fish per replication) with different levels of YMM: SBM (control group), H25, H50, H75, and H100, for 8 weeks. The results showed that dietary YMM significantly increased final body weight (FW), weight gain (WG), and protein efficiency ratio (PER) in H25 group (P < 0.05), however, complete substitution showed the opposite trend (P < 0.05 for FW and WG). The liver antioxidant capacity was improved, manifested by enhanced superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities, glutathione (GSH) content and up-regulated antioxidant-related genes mediated by the Keap1-Nrf2 signaling pathway in the H25 group (P < 0.05). However, in the H100 group oxidative stress occurred in parallel with impairment of hepatic function. Intestinal inflammation was aggravated in the H100 group as evidenced by the up-regulated pro-inflammatory gene expression mediated by the NF-κB pathway (P < 0.05). Additionally, the activity of intestinal digestive enzymes for the grass carp was significantly reduced and accompanied with intestinal mucosal barrier dysfunction in the H100 group (P < 0.05). In summary, replacement of SBM with 25% YMM showed positive influences on growth, antioxidant capacity, immunity, and intestinal health. Conversely, complete replacement of SBM with YMM triggered oxidative stress, caused liver function disorder, and impaired intestinal health in grass carp.

This study was undertaken to reduce reliance on imported soybeans, enhance aquaculture industry resilience, and seek functional soybean meal substitutes. Seven hundred fifty juvenile grass carp (Ctenopharyngodon idella) (initial weight: 24.00 +/- 0.00 g) were assigned to five diets-soybean meal (SM), cottonseed meal (CM), cottonseed protein concentrate (CPC), and CM with 375 or 825 mu g/kg (CMS1 or CMS2) sanguinarine-and, after eight weeks, evaluated for growth, liver and intestinal health, and bile acid metabolism. The results demonstrated that the CMS1 or CMS2 group significantly increased WGR and SGR, reduced FCR, enhanced serum and bile biochemical indices compared with CM group. Besides, histopathological examination of the CM group revealed hepatocellular damage, increased lipid droplet accumulation, elevated glycogen deposition, and more severe fibrosis, along with degeneration of gallbladder columnar epithelium; these lesions were markedly attenuated in the CMS1 and CMS2 groups. In the CM group, intestinal villi and microvilli were disrupted, goblet cell counts declined, and macrophage infiltration alongside widened tight junctions was evident; CMS1 and CMS2 groups markedly restored mucosal architecture to levels comparable with the SM and CPC groups. Finally, the CM group exhibited significant upregulation of lipogenic genes (PPAR-gamma, SREBP1, FAS, ACC1, SCD and DGAT), alongside moderate increases in lipolytic genes (ATGL, HSL, LXR, PPAR-alpha, CPT, and APOE) relative to SM, CMS1, and CMS2 groups. Dietary sanguinarine supplementation markedly enhanced bile acid metabolism, as demonstrated by the upregulation of ABCC2, ABCB11b, CYP7A1, CYP7b1, FGF19, TGR5, SLC10A2 and CCK, together with the concomitant downregulation of SHP. Our findings demonstrate that supplementation of sanguinarine in cottonseed meal diets ameliorates hepatic lipid accumulation, bile acid dysregulation, and tissue damage by suppressing the LXR-PPAR-SREBP1 lipogenic pathway and activating the FXR-SHP/FGF19-CYP7A1 regulatory axis, ultimately enhancing liver and intestinal health and promoting growth performance in grass carp.

This study aimed to investigate the regulatory effects of ginseng polysaccharides (GP) on growth impairment and intestinal injury induced by high-cottonseed meal (CM) diets in grass carp. Juvenile fish (50.01 ± 0.13 g) were randomly assigned to four dietary groups (three replicates per group): control (CON), CM, and CM supplemented with 500 mg/kg (CMGP1) or 1000 mg/kg (CMGP2) of GP. The CM diet significantly suppressed growth and induced intestinal damage, evidenced by elevated pro-inflammatory cytokines, reduced expression of tight junction-related genes, and increased apoptosis-related gene expression. GP supplementation notably improved growth performance compared to the CM group. Additionally, GP alleviated CM-induced oxidative stress by upregulating nrf2 gene expression and downregulating keap1 gene expression. It also suppressed activation of the NF-κB/TLR signaling pathway, decreasing the expression of pro-inflammatory cytokines (e.g., tnf-α, il-1β, il-6) and increasing anti-inflammatory markers (e.g., il-10, tgf-β1). GP further modulated gut microbial composition by reducing Aeromonas and increasing Acinetobacter and Streptococcus abundances. Correlation analysis revealed a strong association between microbial modulation and improved intestinal integrity. Collectively, these findings suggest that GP can effectively counteract the negative effects of high-CM diets on growth and intestinal health through antioxidative, anti-inflammatory, and microbiota-modulating mechanisms in grass carp.

The present study was to evaluate the effects of different levels of soybean meal (SBM) substitute for fish meal (FM) on the growth performance, antioxidant capacities, and intestine health of Asian red-tailed catfish, Hemibagrus wyckioides. Five isonitrogenous and isolipidic diets were prepared: the FM diets contained 50 % fish meal, based on which four SBM diets were formulated as substitutes for 15 %, 30 %, 45 % and 60 % FM in the FM group diets, namely SBM15, SBM30, SBM45, and SBM60. Compared with the FM group, the SBM45 and SBM60 groups exhibited significantly elevated serum glutamate pyruvate transaminase (GPT) levels and showed evidence of liver oxidative stress injury. Concurrently, there were decreases in triglyceride (TG) and total cholesterol (TC) levels (P < 0.05). Besides, hepatic antioxidant enzyme activities and nrf2 gene expression levels were markedly upregulated in the SBM45 and SBM60 groups (P < 0.05). In the SBM45 and SBM60 groups, the lamina propria of the intestinal villi became wider, and the number of goblet cells increased. The tight junction proteins zo-1, claudin-4 and occludin were significantly downregulated in the SBM45 and SBM60 groups. At the same time, the pro-inflammatory factors inos, tgf-(1, tnf-alpha and il-1(1 were significantly upregulated in these two groups (P < 0.05). The SBM45 and SBM60 diets contributed to significant alterations in the intestinal microbiota. In the SBM60 group, the relative abundances of Cetobacterium and Lawsonia significantly increased, and the intestinal micro- biota function was predicted to undergo upregulation of complex carbohydrate metabolism and fermentation. The results of the broken-line regression analysis for FCR and SGR indicate that the optimal substitution level of FM with SBM for H. wyckioides feed is estimated to be 36.83 %-37.31 %. Substitution levels exceeding this range, such as 45 % and 60 %, adversely affect liver and intestinal health.