Effects of selenoprotein extracts from Cardamine hupingshanensis on growth, selenium metabolism, antioxidant capacity, immunity and intestinal health in largemouth bass Micropterus salmoides.

This study aimed to assess the impact of dietary selenoprotein extracts from Cardamine hupingshanensis (SePCH) on the growth, hematological parameters, selenium metabolism, immune responses, antioxidant capacities, inflammatory reactions and intestinal barrier functions in juvenile largemouth bass (Micropterus salmoides). The base diet was supplemented with four different concentrations of SePCH: 0.00, 0.30, 0.60 and 1.20 g/Kg (actual selenium contents: 0.37, 0.59, 0.84 and 1.30 mg/kg). These concentrations were used to formulate four isonitrogenous and isoenergetic diets for juvenile largemouth bass during a 60-day culture period. Adequate dietary SePCH (0.60 and 1.20 g/Kg) significantly increased weight gain and daily growth rate compared to the control groups (0.00 g/Kg). Furthermore, 0.60 and 1.20 g/Kg SePCH significantly enhanced amounts of white blood cells, red blood cells, platelets, lymphocytes and monocytes, and levels of hemoglobin, mean corpuscular volume and mean corpuscular hemoglobin in the hemocytes. In addition, 0.60 and 1.20 g/Kg SePCH increased the mRNA expression levels of selenocysteine lyase, selenophosphate synthase 1, 15 kDa selenoprotein, selenoprotein T2, selenoprotein H, selenoprotein P and selenoprotein K in the fish liver and intestine compared to the controls. Adequate SePCH not only significantly elevated the activities of antioxidant enzymes (Total superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase), the levels of total antioxidant capacity and glutathione, while increased mRNA transcription levels of NF-E2-related factor 2, Cu/Zn-superoxide dismutase, catalase, glutathione reductase and glutathione peroxidase. However, adequate SePCH significantly decreased levels of malondialdehyde and H2O2 and the mRNA expression levels of kelch-like ECH-associated protein 1a and kelch-like ECH-associated protein 1b in the fish liver and intestine compared to the controls. Meanwhile, adequate SePCH markedly enhanced the levels of immune factors (alkaline phosphatase, acid phosphatase, lysozyme, complement component 3, complement component 4 and immunoglobulin M) and innate immune-related genes (lysozyme, hepcidin, liver-expressed antimicrobial peptide 2, complement component 3 and complement component 4) in the fish liver and intestine compared to the controls. Adequate SePCH reduced the levels of pro-inflammatory cytokines (tumour necrosis factor-α, interleukin 8, interleukin 1ß and interferon γ), while increasing transforming growth factor ß1 levels at both transcriptional and protein levels in the liver and intestine. The mRNA expression levels of mitogen-activated protein kinase 13 (MAPK 13), MAPK14 and nuclear factor kappa B p65 were significantly reduced in the liver and intestine of fish fed with 0.60 and 1.20 g/Kg SePCH compared to the controls. Histological sections also demonstrated that 0.60 and 1.20 g/Kg SePCH significantly increased intestinal villus height and villus width compared to the controls. Furthermore, the mRNA expression levels of tight junction proteins (zonula occludens-1, zonula occludens-3, Claudin-1, Claudin-3, Claudin-5, Claudin-11, Claudin-23 and Claudin-34) and Mucin-17 were significantly upregulated in the intestinal epithelial cells of 0.60 and 1.20 g/Kg SePCH groups compared to the controls. In conclusion, these results found that 0.60 and 1.20 g/Kg dietary SePCH can not only improve growth, hematological parameters, selenium metabolism, antioxidant capacities, enhance immune responses and intestinal functions, but also alleviate inflammatory responses. This information can serve as a useful reference for formulating feeds for largemouth bass.

Exploring the impact of nano-Se and nano-clay feed supplements on interleukin genes, immunity and growth rate in European Sea Bass (Dicentrarchus labrax).

This study aimed to investigate the effects of adding Nano-Selenium (NSe) and Nano-clay (NC) as feed supplements on European Sea Bass (Dicentrarchus labrax). Two separate experiments were conducted, one with NC and the other with NSe. Each experiment consisted of four sub-groups with varying concentrations of NC or NSe. The expression levels of five immune-related genes (TNF-α, TNF-ß, IL-2, IL-6 and IL-12) were measured using Real-time Quantitative PCR (Rt-PCR) Assay. The results showed an increase in the expression of interleukins (IL-2, IL-6 and IL-12) and pro-inflammatory cytokines (TNF-α and TNF-ß) after exposure to NC and NSe. TNF-α gene expression was significantly higher with both 1 mg and 10 mg concentrations of NC and NSe. TNF-ß gene expression was highest with the 5 mg concentration of NC. The concentrations of 1 mg and 10 mg for NC, and 1 mg, 5 mg, and 10 mg for NSe, led to the highest (p < 0.05) levels of IL-2 expression compared to the control. Similar trends were observed for IL-6 and IL-12 gene expression. Understanding the impact of these concentrations on gene expression, growth rate, biochemical indices, and antioxidant status can provide valuable insights into the potential applications of NC and NSe supplements on European Sea Bass.

Excessive dietary iron exposure increases the susceptibility of largemouth bass (Micropterus salmoides) to Aeromonas hydrophila by interfering with immune response, oxidative stress, and intestinal homeostasis.

Iron is an essential cofactor in the fundamental metabolic pathways of organisms. Moderate iron intake can enhance animal growth performance, while iron overload increases the risk of pathogen infection. Although the impact of iron on the pathogen-host relationship has been confirmed in higher vertebrates, research in fish is extremely limited. The effects and mechanisms of different levels of iron exposure on the infection of Aeromonas hydrophila in largemouth bass (Micropterus salmoides) remain unclear. In this study, experimental diets were prepared by adding 0, 800, 1600, and 3200 mg/kg of FeSO4∙7H2O to the basal feed, and the impact of a 56-day feeding period on the mortality rate of largemouth bass infected with A. hydrophila was analyzed. Additionally, the relationships between mortality rate and tissue iron content, immune regulation, oxidative stress, iron homeostasis, gut microbiota, and tissue morphology were investigated. The results showed that the survival rate of largemouth bass infected with A. hydrophila decreased with increasing iron exposure levels. Excessive dietary iron intake significantly increased iron deposition in the tissues of largemouth bass, reduced the expression and activity of antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase, increased the content of lipid peroxidation product malondialdehyde, and thereby induced oxidative stress. Excessive iron supplementation could influence the immune response of largemouth bass by upregulating the expression of pro-inflammatory cytokines in the intestine and liver, while downregulating the expression of anti-inflammatory cytokines. Additionally, excessive iron intake could also affect iron metabolism by inducing the expression of hepcidin, disrupt intestinal homeostasis by interfering with the composition and function of the gut microbiota, and induce damage in the intestinal and hepatic tissues. These research findings provide a partial theoretical basis for deciphering the molecular mechanisms underlying the influence of excessive iron exposure on the susceptibility of largemouth bass to pathogenic bacteria.

Expression characteristics of the cyp19a1b aromatase gene and its response to 17ß-estradiol treatment in largemouth bass (Micropterus salmoides).

To investigate the regulatory role of the cyp19a1b aromatase gene in the sexual differentiation of largemouth bass (Micropterus salmoides, LMB), we obtained the full-length cDNA sequence of cyp19a1b using rapid amplification of cDNA ends technique. Tissue expression characteristics and feedback with 17-ß-estradiol (E2) were determined using quantitative real-time PCR (qRT-PCR), while gonad development was assessed through histological section observations. The cDNA sequence of LMB cyp19a1b was found to be1950 base pairs (bp) in length, including a 5' untranslated region of 145 bp, a 3' untranslated region of 278 bp, and an open reading frame encoding a protein consisting of 1527 bp that encoded 508 amino acids. The qRT-PCR results indicated that cyp19a1b abundantly expressed in the brain, followed by the gonads, and its expression in the ovaries was significantly higher than that observed in the testes (P < 0.05). After feeding fish with E2 for 30 days, the expression of cyp19a1b in the pseudo-female gonads (XY-F) was significantly higher than that in males (XY-M) (P < 0.05), whereas expression did not differ significantly between XX-F and XY-F fish (P > 0.05). Although the expression of cyp19a1b in XY-F and XX-F fish was not significantly different after 60 days (P>0.05), both exhibited significantly higher levels than that of XY-M fish (P<0.05). Histological sections analysis showed the presence of oogonia in both XY-F and XX-F fish at 30 days, while spermatogonia were observed in XY-M fish. At 60 days, primary oocytes were abundantly observed in both XY-F and XX-F fish, while a few spermatogonia were visible in XY-M fish. At 90 days, the histological sections' results showed that a large number of oocytes were visible in XY-F and XX-F fish. Additionally, the gonads of XY-M fish contained numerous spermatocytes. These results suggest that cyp19a1b plays a pivotal role in the development of ovaries and nervous system development in LMB.

Dietary sodium butyrate positively modulated intestinal microbial community, but did not promote growth of largemouth bass (Micropterus salmoides).

This study investigated the effects of dietary sodium butyrate (NaB) on growth, serum biochemical indices, intestine histology, and gut microbiota of largemouth bass (Micropterus salmoides). A basal diet was formulated and used as the control diet (Con), and five additional diets were prepared by supplementing NaB (50%) in the basal diet at 2.0, 4.0, 8.0, 12.0, and 16.0 g/kg inclusion (NaB-2, NaB-4, NaB-8, NaB-12, and NaB-16 diets). Then, the six diets were fed to triplicate groups of largemouth bass juveniles (2.4 ± 0.1 g) for 8 weeks. NaB supplementation linearly and quadratically affected weight gain (WG) and feed intake (FI) (P < 0.05). The NaB-16 group displayed lower WG (- 6.8%) and FI than the Con group (P < 0.05), while no differences were found in WG and feed conversion ratio between the other NaB groups and Con group (P > 0.05). Serum alkaline phosphatase and lysozyme activities were higher in the NaB groups (P < 0.05), and D-lactate content was lower in the NaB-12 group (P < 0.05) than the control. Intestinal lipase activity in NaB-2, NaB-4 group, and villi width in NaB-8 group were also higher than those in the Con group (P < 0.05). Compared to the Con group, the intestinal abundances of Firmicutes and Mycoplasma were increased and the abundances of Proteobacteria, Achromobacter and Plesiomonas were decreased in NaB-4 and NaB-16 groups (P < 0.05). In conclusion, dietary NaB did not promote the growth of juvenile largemouth bass, but positively modulated the intestinal microbial community.

Characterization of active films based on chitosan/polyvinyl alcohol integrated with ginger essential oil-loaded bacterial cellulose and application in sea bass (Lateolabrax japonicas) packaging.

The poor mechanical properties, low water-resistance, and limited antimicrobial activity of chitosan (CS)/polyvinyl alcohol (PVA) based film limited its application in aquatic product preservation. Herein, bacterial cellulose (BC) was used to load ginger essential oil (GEO). The effects of the addition of BC and different concentrations of GEO on the physicochemical and antimicrobial activities of films were systematically evaluated. Finally, the application of sea bass fillets was investigated. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis (XRD) analysis indicated dense networks were formed, which was verified by enhanced physical properties. The mechanical properties, barrier properties, and antimicrobial activities enhanced as GEO concentration increased. CPB0.8 (0.8 % GEO) film had better tensile strength (TS) and barrier performance, improved the quality, and extended the shelf-life of sea bass for another 6 days at least. Overall, active films are potential packaging materials for aquatic products.

Rhein: A potent immunomodulator empowering largemouth bass against MSRV infection.

Micropterus salmoides rhabdovirus (MSRV) is a significant viral pathogen in largemouth bass aquaculture, causing substantial annual economic losses. However, effective prevention methods remain elusive for various reasons. Medicinal plant extracts have emerged as valuable tools in preventing and managing aquatic animal diseases. Thus, the search for immunomodulators with straightforward, safe structures in plant extracts is imperative to ensure the continued health and growth of the largemouth bass industry. In our research, we employed epithelioma papulosum cyprinid (EPC) cells and largemouth bass as models to assess the anti-MSRV properties and immunomodulatory effects of ten plant-derived bioactive compounds. Among them, rhein demonstrated noteworthy potential, exhibiting a 75 % reduction in viral replication in vitro at a concentration of 50 mg/L. Furthermore, rhein pre-treatment significantly inhibited MSRV genome replication in EPC cells, with the highest inhibition rate reaching 64.8 % after 24 h, underscoring rhein's preventive impact against MSRV. Likewise, rhein displayed remarkable therapeutic effects on EPC cells during the early stages of MSRV infection, achieving a maximum inhibition rate of 85.6 % in viral replication. Subsequent investigations unveiled that rhein, with its consistent activity, effectively mitigated cytopathic effects (CPE) and nuclear damage induced by MSRV infection. Moreover, it restrained mitochondrial membrane depolarization and reduced the apoptosis rate by 38.8 %. In vivo experiments reinforced these findings, demonstrating that intraperitoneal injection of rhein enhanced the expression levels of immune related genes in multiple organs, hindered virus replication, and curtailed the mortality rate of MSRV-infected largemouth bass by 29 %. Collectively, our study endorses the utility of rhein as an immunomodulator to combat MSRV infections in largemouth bass. This not only underscores the potential of rhein as a broad-spectrum antiviral and means to bolster the immune response but also highlights the role of apoptosis as an immunological marker, making it an invaluable addition to the armamentarium against aquatic viral pathogens.

Effects of Ocimum basilicum essential oil and ginger extract on serum biochemistry, oxidative stress and gill tissue damage of pearl gentian grouper during simulated live transport.

This study explored the effects of the essential oil of Ocimum basilicum (EOOB) and ginger extract (GE) during the transportation of pearl gentian grouper from water quality, serum biochemistry, oxidative stress, meat flavor, and gill tissue morphology. Fish (450 ± 50 g) were allocated to the following 5 treatments: control group (fish transported in water only), 5 mg/LEOOB, 10 mg/LEOOB, 3 mg/LGE, and 6 mg/LGE and transported in insulation boxes (66 × 51 × 37.8 cm) for 72 h. Samples were taken at 0, 12, 36, 60, and 72 h immediately after transport. It was found that 10 mg/LEOOB and 6 mg/LGE could reduce the levels of total ammonia nitrogen (TAN), dissolved oxygen (DO), water pH, serum glucose (GLU), cortisol (COR), liver superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), and glutathione peroxidase (GPX), increase the activities of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH), as well as significantly increase the total free amino acid (TFAA) content in muscle compared to the control group (P < 0.05). In addition, by observing the microstructure of gill tissue, it was found that compared with untreated grouper, the morphological damage of gill tissue in EOOB and GE treatment was alleviated. These results indicated that adding appropriate amounts of EOOB and GE to transport water could improve the water quality, relieve stress, and lower energy metabolism of grouper during transport. The results of this research will help to improve the survival rate of grouper after transportation and decrease economic losses to fishery.

Optimal dietary zinc inclusion improved growth performance, serum antioxidant capacity, immune status, and liver lipid and glucose metabolism of largemouth bass (Micropterus salmoides).

This study was conducted to ascertain the effect of dietary Zn on growth and health status of juvenile largemouth bass (Micropterus salmoides). Six experimental diets with Zn level of 50.17, 56.74, 73.34, 86.03, 123.94, and 209.20 mg/kg, respectively were compounded using complex amino acid-chelated zinc, and were fed to juvenile fish (5.50 ± 0.10 g) for 70 d. The specific growth rate (SGR) varied with dietary Zn level in a quadratic model and peaked at the 73.34 mg/kg group, while the feeding rate exhibited an opposite trend (P < 0.05). The condition factor, hepatosomatic index and mesenteric fat index all exhibited a tendency similar with SGR (P < 0.05). Dietary Zn level affected serum total proteins, urea, triglycerides, and glucose (P < 0.05). Serum Zn and copper levels linearly increased with dietary Zn level, while serum iron and manganese showed the opposite trend. Serum superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) increased with dietary Zn level and reached a plateau at 86.03 mg/kg. Serum complement component 3 (C3), IgM, and lysozyme also were enhanced by 73.34 mg/kg Zn. Body protein content increased with zinc level up to 73.34 mg/kg, and then remained steadily. As dietary Zn level increased, hepatic lipid level increased and then reached a plateau at 86.03 mg/kg group, while glycogen increased linearly. Moreover, gene expression related to lipid and glycogen metabolism from liver transcriptome further explained the liver lipid and glycogen variations. To conclude, a dietary Zn requirement of 76.99 mg/kg was suggested for juvenile largemouth bass to improve growth, antioxidant capacity, and immune status.

Mercury and selenium in three fish species from a dam 20 months after a mine-tailing spill in the SE Gulf of California ecoregion, Mexico.

During January 2013, a mining spill occurred in the Santa Maria mining region, releasing around 300,000 m3 of tailings on Los Remedios river, which was transported through the San Lorenzo river and finally to El Comedero (EC) dam. Twenty months later, we examined the concentrations of Hg and Se in the muscle, liver, gills, and guts of three fish species (Cyprinus carpio, Oreochromis aureus, Micropterus salmoides) captured in the EC dam to assess the performance of the cleaning operations. A high Se concentration in the liver of all species (carp, 1.2 ± 0.4; tilapia, 3.9 ± 2.1; bass, 3.5 ± 1.1 µg g-1 ww) was consistently observed, while this behavior was only found in the blue tilapia for Hg (0.15 ± 0.11 µg g-1 ww). Tilapia (benthic-detritivorous) exhibited the highest Se concentrations compared to the carp (omnivore) and the largemouth bass (piscivore). In contrast, the largemouth bass had the highest Hg levels in the muscle compared with the other fishes. Such differences could be related to the different metabolism and feeding habits among species. Compared to a tilapia study carried out three months after the mine spill during a mortality event, a decrease was evident in the liver for Se and Hg by 7.2 and 4.7 times, respectively. This reveals that cleaning operations were more efficient for Se and less for Hg, and that a prolonged period was required for the partial recovery of the element levels in fish from sites impacted by mining. Considering the Mexican consumption scenarios for each fish species, it could be concluded that there will be no non-cancer risk by exposure to Hg or Se.

An integrated study of glutamine alleviates enteritis induced by glycinin in hybrid groupers using transcriptomics, proteomics and microRNA analyses.

Glutamine has been used to improve intestinal development and immunity in fish. We previously found that dietary glutamine enhances growth and alleviates enteritis in juvenile hybrid groupers (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂). This study aimed to further reveal the protective role of glutamine on glycinin-induced enteritis by integrating transcriptome, proteome, and microRNA analyses. Three isonitrogenous and isolipidic trial diets were formulated: a diet containing 10% glycinin (11S group), 10% glycinin diet supplemented with 2% alanine-glutamine (Gln group), and a diet containing neither glycinin nor alanine-glutamine (fishmeal, FM group). Each experimental diet was fed to triplicate hybrid grouper groups for 8 weeks. The analysis of intestinal transcriptomic and proteomics revealed a total of 570 differentially expressed genes (DEGs) and 169 differentially expressed proteins (DEPs) in the 11S and FM comparison group. Similarly, a total of 626 DEGs and 165 DEPs were identified in the Gln and 11S comparison group. Integration of transcriptome and proteome showed that 117 DEGs showed consistent expression patterns at both the transcriptional and translational levels in the Gln and 11S comparison group. These DEGs showed significant enrichment in pathways associated with intestinal epithelial barrier function, such as extracellular matrix (ECM)-receptor interaction, tight junction, and cell adhesion molecules (P < 0.05). Further, the expression levels of genes (myosin-11, cortactin, tenascin, major histocompatibility complex class I and II) related to these pathways above were significantly upregulated at both the transcriptional and translational levels (P < 0.05). The microRNA results showed that the expression levels of miR-212 (target genes colla1 and colla2) and miR-18a-5p (target gene colla1) in fish fed Gln group were significantly lower compared to the 11S group fish (P < 0.05). In conclusion, ECM-receptor interaction, tight junction, and cell adhesion molecules pathways play a key role in glutamine alleviation of hybrid grouper enteritis induced by high-dose glycinin, in which miRNAs and target mRNAs/proteins participated cooperatively. Our findings provide valuable insights into the RNAs and protein profiles, contributing to a deeper understanding of the underlying mechanism for fish enteritis.

Dietary glycine supplementation improves the growth performance of 110- to 240-g (phase II) hybrid striped bass (Morone saxatilis â™€× Morone chrysops ♂) fed soybean meal-based diets.

We recently reported that supplementing glycine to soybean meal (SBM)-based diets is necessary for optimum growth of 5- to 40-g (phase I) hybrid striped bass (HSB). The present study tested the hypothesis that supplementing glycine to SBM-based diets may enhance the growth of 110- to 240-g (phase II) HSB. HSB (the initial body weight of approximately 110 g) were fed an SBM (58%)-based diet supplemented with 0%, 1%, or 2% of glycine, with l-alanine serving as the isonitrogenous control. There were four tanks per dietary group, with four fish per tank. The fish were fed their respective diets to apparent satiation twice daily. The feed intake and body weight of fish were recorded daily and every 2 wk, respectively. At the end of the 56-d feeding trial, plasma and tissue samples were collected to determine amino acid concentrations and histological alterations, and tissues were used to measure the oxidation of l-glutamate, l-glutamine, l-aspartate, and glycine. Results showed that dietary supplementation with 1% and 2% glycine dose-dependently increased (P < 0.05) the concentration of glycine in the plasma of HSB by 48% and 99%, respectively. Compared with the 0%-glycine group, dietary supplementation with 1% glycine did not affect (P > 0.05) the feed intake of HSB but increased (P < 0.05) their final body weight, weight gain, and gain:feed ratio during the whole period by 13%, 29%, and 21%, respectively. Compared with the 1% glycine group, dietary supplementation with 2% glycine increased (P < 0.05) the feed intake, final body weight, and weight gain of HSB by 13%, 7%, and 14%, respectively. Compared with the 0%-glycine group, fish fed with the 1%-glycine and 2%-glycine diets had a greater (P < 0.05) villus height in the proximal intestine, when compared with the 0%-glycine group. Collectively, these results indicated that SBM-based diets did not provide sufficient glycine for phase II HSB (110 to 240 g) and that dietary glycine supplementation is essential for their optimum growth and intestinal structure.

Glycine is the simplest but the most abundant amino acid in the bodies of animals including fish and pigs. The content of glycine in plant-sourced feedstuffs (e.g., soybean meal) is generally low. Glycine can be synthesized de novo in all animals and, therefore, has traditionally been classified as a nutritionally nonessential amino acid for fish and mammals. However, a capacity for the synthesis of glycine does not necessarily mean its adequate formation by animals. Growing evidence shows that either neonatal pigs fed milk protein-based diets or postweaning pigs regardless of their birth weights do not synthesize sufficient glycine, and must ingest supplemental glycine (e.g., 1% in diets) for optimum growth performance. Similar results have been reported for 5- to 40-g (phase I) juvenile hybrid striped bass (HSB) fed and largemouth bass fed soybean meal-based diets. The present study tested the hypothesis that supplementing glycine to soybean meal-based diets may enhance the growth of 110- to 240-g (phase II) HSB. Results of the current investigation indicate that glycine is also inadequate for normal intestinal structure or maximum growth in phase II HSB fed soybean meal-based diets. Supplementing 1% or 2% glycine to these diets increased protein accretion, weight gain, and feed efficiency in HSB while improving their intestinal structure. These findings indicate an important role for a sufficient provision of dietary glycine in the optimal nutrition, health, and growth of finishing HSB, and have broad implications for developing low-fishmeal diets to enhance fish production and sustain animal agriculture (including aquaculture).

Effects of sodium butyrate on growth performance, antioxidant status, inflammatory response and resistance to hypoxic stress in juvenile largemouth bass (Micropterus salmoides).

The aim of this study was to investigate the effects of sodium butyrate (SB) supplementation on growth performance, antioxidant enzyme activities, inflammatory factors, and hypoxic stress in largemouth bass (Micropterus salmoides). Diets were supplemented with different doses of SB at 0 (SB0), 0.5 (SB1), 1.0 (SB2) and 2.0 (SB3) g/kg. The hypoxic stress experiment was performed after 56 days of culture. The results showed that compared with the SB0 group, the final body weight, weight gain rate and protein deposition rate of the SB3 group were significantly increased (P<0.05), while FCR was significantly decreased (P<0.05). The contents of dry matter, crude lipids, and ash in the SB2 group were significantly higher than those in the SB0 group (P<0.05). The urea level was significantly decreased (P<0.05), and the glucose content was significantly increased (P<0.05) in the SB supplement group. Compared with the SB0 group, the SB2 group had significant reductions in the levels of serum triglyceride, cholesterol, elevated-density lipoprotein cholesterol, and low-density lipoprotein (P<0.05), and significant reductions in the levels of liver alkaline phosphatase and malondialdehyde (P<0.05). The total antioxidant capacity of the SB1 group was higher than that of other groups (P<0.05). Compared with the SB0 group, the mRNA expression of TLR22, MyD88, TGF-ß1, IL-1ß and IL-8 in the SB2 group significantly decreased (P<0.05). The cumulative mortality rate was significantly decreased in the SB2 and SB3 groups in comparison with that in the SB0 group after three hours of hypoxic stress (P<0.05). In a 56-day feeding trial, SB enhanced largemouth bass growth by increasing antioxidant enzyme activity and inhibiting TLR22-MyD88 signaling, therefore increasing cumulative mortality from hypoxic stress in largemouth bass.

Vitamin D3 can effectively and rapidly clear largemouth bass ranavirus by immunoregulation.

Largemouth bass ranavirus (LMBV) is a highly destructive pathogen that causes significant mortality rates among largemouth bass populations. Unfortunately, there is a dearth of drug development efforts specifically aimed at treating LMBV. To address this, our study sought to investigate the potential effectiveness of incorporating varying doses of VD3 into the diet as a treatment for LMBV. Through qRT-PCR and semi-qPCR, we observed significant suppression and clearance of LMBV pathogens in largemouth bass fed with 15000 IU/Kg and 20000 IU/Kg of VD3 within 14 days. In addition, VD3 treatment significantly increased the expression levels of key immune-related genes such as IL-1ß, IFN-γ, Mx, and IgM. Encouragingly, we observed that VD3 significantly increased antioxidant and immune activities such as TSOD, TAOC and C3 in serum and maintained total protein levels. Additionally, tissue pathology sections highlighted a dose-dependent relationship between VD3 supplementation and tissue damage, with the 15000 IU and 20000 IU groups exhibiting minimal damage. In conclusion, a reasonable concentration of VD3 effectively reduced LMBV replication and tissue damages, while improved immune-related genes expression and serum biochemical indices. These findings declare the considerable therapeutic potential of VD3 supplementation for combating LMBV disease and provide an alternative treatment option for fish farming.

Integrated analysis of microbiome and host transcriptome reveals the damage/protective mechanism of corn oil and olive oil on the gut health of grouper (♀ Epinephelus fuscoguttatus × â™‚ E. lanceolatu).

As digestive and immune organs of animals, the gut was frequently used to evaluate the health status of aquatic animals. In previous oil source alternatives study, corn oil (CO) had been found to induce gut inflammation, while olive oil (OO) had been found to be effective in protecting intestinal health. Three diets with different oil sources (fish oil, CO, OO) were formulated for an 8-week culture experiment, and it was proposed to combine 16S sequencing and transcriptome sequencing analysis to preliminarily elucidate the damage/protection mechanism of CO and OO on the gut health of grouper (♀ Epinephelus fuscoguttatus × â™‚ E. lanceolatu). We found that CO indeed damaged to gut health and destroyed the gut structure, while OO had a positive outcome in protecting the gut structure, promoting digestibility and relieving enteritis. Photobacterium, Romboutsia and Epulopiscium were significantly enriched in OO group and Staphylococcus were significantly enriched in CO group. Transcriptome sequencing further revealed CO could activated Complement and coagulation cascades, Staphylococcus aureus infection, Systemic lupus erythematosus, and Tuberculosis pathways; conversely, OO activated B-cell signaling receptors, promoted B-cell proliferation and apoptosis, and thus activated B-cell signaling pathways to enhance immunity, whereas OO can regulate IL17 signaling pathway and TNF signaling pathway to inhibit NF-κB signaling pathway to reduce pro-inflammatory response. By integrating the microbiome and transcriptome, further identified all differential microorganisms were directly and significantly correlated with differential genes, and Clostridium_sensu_stricto_1, Romboutsia, Staphylococcus might as the core regulates the expression of differential gene in the organism. These results reveal that different oil sources alter gut gene expression mainly by modulating the composition and abundance of gut microbiota, further regulating the health status of the gut. Gut microbiota could be used as biomarkers to provide reference and solutions for the mitigation of inflammation in aquatic animals.

Dietary glycine supplementation enhances the growth performance of hybrid striped bass (Morone saxatilis â™€× Morone chrysops ♂) fed soybean meal-based diets.

This study was conducted to test the hypothesis that supplementing 1% and 2% glycine to soybean meal (SBM)-based diets can improve the growth performance of juvenile hybrid striped bass (HSB). The basal diets contained 15% fishmeal and 58% SBM (DM basis). Alanine was used as the isonitrogenous control in different diets. All diets contained 44% crude protein and 10% lipids (DM basis). There were four tanks (15 fish per tank) per dietary group, with the mean of the initial body weight (BW) of fish being 5.3 g. Fish were fed to apparent satiation twice daily, and their BW was recorded every 2 wk. The trial lasted for 8 wk. Results indicated that the BW, weight gain, protein efficiency ratio, and retention of dietary lipids in fish were enhanced (P < 0.05) by dietary supplementation with 1% or 2% glycine. In addition, dietary supplementation with glycine did not affect (P > 0.05) the feed intake of fish but increased (P < 0.05) the retention of dietary nitrogen, most amino acids, and phosphorus in the body, compared to the 0% glycine group. Dietary supplementation with 1% and 2% glycine dose-dependently augmented (P < 0.05) the villus height of the proximal intestine and reduced the submucosal thickness of the gut, while preventing submucosal and lamina propria hemorrhages. Compared with the 0% glycine group, dietary supplementation with 1% or 2% glycine decreased (P < 0.05) the proportion of skeletal-muscle fibers with diameters of 40 to 60 µm but increased (P < 0.05) the proportion of skeletal-muscle fibers with diameters of 80 to 100 µm and > 100 µm. Collectively, these findings indicate that glycine in SBM-based diets is inadequate for maximum growth of juvenile HSB and that dietary supplementation with 1% or 2% glycine is required to improve their weight gain and feed efficiency. Glycine is a conditionally essential amino acid for this fish.

Animal agriculture (including aquaculture) provides high-quality protein for improving human nutrition and health. The United States is the top producer of hybrid striped bass (HSB) in the world as both food and sport fish. Fishmeal has traditionally been used as the major protein feedstuff in HSB diets, but feeding fish with fishmeal is not sustainable in the industry. Over the past four decades, there have been extensive studies to replace fishmeal with plant-sourced feedstuffs (mainly soybean meal) in aquafeeds at variable success. It has now been recognized that the content of glycine (the most abundant amino acid in the animal body) in soybean meal is only about half of that in fishmeal. Results of this study indicate that glycine is inadequate for normal intestinal structure or maximum growth in HSB fed soybean meal-based diets. Supplementing 1% or 2% glycine to these diets increased protein accretion, skeletal-muscle hypertrophy, and weight gain in HSB, while improving their intestinal structure. These findings indicate an important role for a sufficient provision of dietary glycine in the optimal nutrition, health, and growth of HSB, and have broad implications for developing low-fishmeal diets to enhance fish production and sustain animal agriculture.

High starch diets attenuate the immune function of Micropterus salmoides immune organs by modulating Keap1/Nrf2 and MAPK signaling pathways.

Based on their good physiological functions and physical properties, carbohydrates are widely used in fish feed. However, excessive use of carbohydrates such as starch in fish feed may reduce the immunity of the fish and cause a series of health problems. In order to more clearly clarify the effects of different starch levels in feed on the immune organs of Micropterus salmoides, this study took the immune organs as the entry point and explored it from several perspectives, including differences in enzyme activity in plasma, changes in gene expression in immune organs, and resistance to pathogenic bacteria. The results showed that (1) high starch feed activates inflammatory responses in the spleen and head kidney through the MAPK signaling pathway. This leads to a decrease in the number of lymphocytes and weakens the resistance to pathogens; (2) high starch diet affects the antioxidant capacity of the trunk kidney by regulating the Keap1/Nrf2 pathway; (3) There was a strong correlation between gene expression patterns in the head kidney and lysozyme content in plasma. This implies that the high starch diet may regulate lysozyme production by affecting gene expression in the head kidney and further affect immune function. This study helps to reveal the interaction between starch and the immune system and provide scientific basis for the development of reasonable dietary recommendations and disease prevention.

Positive effects of dietary Clostridium butyricum supplementation on growth performance, antioxidant capacity, immunity and viability against hypoxic stress in largemouth bass.

The effects of dietary supplementation of Clostridium butyricum (CB) on growth performance, serum biochemistry, antioxidant activity, mRNA levels of immune-related genes and resistance to hypoxia stress were studied in largemouth bass. Feed with CB0 (control, 0 CFU/kg), CB1 (4.3×108 CFU/kg), CB2 (7.5×108 CFU/kg), CB3 (1.5×109 CFU/kg) and CB4 (3.2×109 CFU/kg) CB for 56 days, and then a 3 h hypoxic stress experiment was performed. The results showed that dietary CB significantly increased the WGR (weight gain rate), SGR (specific growth rate), PDR (protein deposition rate) and ISI (Intestosomatic index) of largemouth bass (P<0.05). Hepatic GH (growth hormone)/IGF-1 (insulin-like growth factor-1) gene expression was significantly upregulated in the CB3 and CB4 groups compared with the CB0 group (P<0.05), while the FC (feed conversion) was significantly decreased (P<0.05). Serum TP (total protein) and GLU (glucose) levels were significantly higher in the CB4 group than in the CB0 group (P<0.05), while the contents of serum AST (aspartate transaminase), ALT (alanine transaminase), AKP (alkline phosphatase) and UN (urea nitrogen) in CB4 were significantly lower than those in CB0 (P<0.05). T-AOC (total antioxidant capacity), SOD (superoxide dismutase), CAT (catalase), POD (peroxidase) and GSH-Px (glutathione peroxidase) activities were significantly higher in CB3 and CB4 groups than in CB0 group (P<0. 05). The liver MDA (malondialdehyde) content of CB1, CB2, CB3 and CB4 groups was significantly higher than that of CB0 group (P<0. 05). The relative expressions of IL-1ß (interleukin 1ß), TNF-α (tumor necrosis factor α) and TLR22 (toll-like receptor-22) genes in CB2, CB3 and CB4 groups were significantly lower than those in CB0 group (P<0.05). The relative expression of IL-8 (malondialdehyde) and MyD88 (Myeloid differentiation factor 88) genes in the CB4 group was significantly lower than that in the CB0 group (P<0.05). The liver LZM (lysozyme) content of CB2, CB3 and CB4 groups was significantly higher than that of CB0 group (P<0. 05). The relative expression of IL-10 (interleukin 10) and TGF-ß (transforming growth factor ß) genes in the CB4 group was significantly higher than that in the CB0 group (P<0.05). Under hypoxic stress for 3 h, the CMR of CB0 group was significantly higher than that of CB1, CB2, CB3 and CB4 groups (P<0.05). Dietary CB can improve the growth performance and resistance to hypoxic stress of largemouth bass by regulating the expression of GH/IGF-1 gene and inflammatory factors and inhibiting TLR22/MyD88 signaling pathway.

Impact of dietary zinc on the growth performance, histopathological analysis, antioxidant capability, and inflammatory response of largemouth bass Micropterus salmoides.

Zinc plays a crucial role in the antioxidant capacity, and inflammatory response of aquatic species, but its impact on largemouth bass Micropterus salmoides is rarely reported. Therefore, this paper aimed to investigate the effects of different levels of zinc on the growth performance, histopathology, antioxidant capacity, and inflammatory cytokines of largemouth bass Micropterus salmoides. Fish with an initial weight of 7.84 ± 0.06 g were cultured for 10 weeks. Five experimental diets were prepared with supplemented proteinate Zn (Bioplex Zn, Alltech) (0, 30, 60, 90, and 120 mg/kg), which were named the Zn-42, Zn-73, Zn-103, Zn-133, and Zn-164 groups. No evident difference was found between the dietary zinc level and the survival rate, the crude lipid content of the whole fish, or the visceral somatic index. Weight gain, condition factor, whole-body crude protein content, interleukin-10, and transforming growth factor beta gene expression were gradually enhanced with up to 102.68 mg/kg zinc and decreased at higher levels. The hepatosomatic index, feed conversion ratio, malondialdehyde level in the liver, aspartate aminotransferase, and alanine transaminase activity in the serum, gradually decreased up to 102.68 mg/kg zinc, and gradually increased beyond this. Activation of the nuclear factor erythroid-derived 2-like 2/Kelch-like ECH-associated protein 1 signaling pathway gradually up-regulated the mRNA levels and activities of glutathione peroxidase, total antioxidant capacity, catalase, and superoxide dismutase in the liver, this antioxidant ability was lower when the zinc was greater than 102.68 mg/kg. The gene expressions of nuclear factor-k-gene binding and pro-inflammation cytokines (interleukin-1ß, interleukin-15, tumor necrosis factor alpha, and interleukin-8) were up-regulated up to 102.68 mg/kg zinc and then gradually repressed. In conclusion, using broken line analysis to estimate weight gain and Zn proteinate as the zinc source, the recommended dietary zinc for largemouth bass is 66.57 mg/kg zinc.

Glutamine improves growth and intestinal health in juvenile hybrid groupers fed high-dose glycinin.

Glutamine addition can improve immunity and intestinal development in fish. This study examined the protective roles of glutamine on growth suppression and enteritis induced by glycinin in juvenile hybrid groupers (female Epinephelus fuscoguttatus × male Epinephelus lanceolatus). The experiment set four isonitrogenous and isolipidic trial diets: a diet containing 10% glycinin (11S), 10% of 11S diet supplemented with 1% or 2% alanine-glutamine (1% or 2% Ala-Gln), and a diet containing neither 11S nor Ala-Gln (FM). A feeding trial was conducted in hybrid grouper for 8 weeks. Weight gain and specific growth rates in Groups 1% and 2% Ala-Gln were significantly higher than those of the 11S group but were similar to those of the FM group. The intestinal muscular layer thickness, plica height and width of the 2% Ala-Gln group were significantly higher than those of Group 11S. The enterocyte proliferation efficiency of the 11S group was significantly lower compared to other groups. Compared with the 11S group, Groups 1% and 2% Ala-Gln fish had increased intestinal lysozyme activities, complement 3 and immunoglobulin M as well as cathelicidin contents. The mRNA levels of tnf-α, il-1ß, ifn-α, and hsp70 genes were more downregulated in Groups 1% and 2% Ala-Gln than in Group 11S. Compared with FM group, fish from the 11S group had significantly lower mRNA levels of myd88, ikkß, and nf-κb p65 genes. These three values in the 2% Ala-Gln group were significantly lower than those in Group 11S but not significantly different from those of Group FM. The relative abundance of Vibrio in Group 11S was higher than that in Groups FM and 2% Ala-Gln. Intestinal glutamine, glutaminase, glutamic acid, α-ketoglutarate, malate dehydrogenase and ATP contents were higher in Groups 1% and 2% Ala-Gln than in Group 11S. These results suggest that glutamine is a useful feed additive to enhance growth and intestinal immunity, alleviate inflammation, and modulate gut microbiota in hybrid grouper fed high-dose glycinin.