Probiotics, prebiotics and synbiotics improved the functionality of aquafeed: Upgrading growth, reproduction, immunity and disease resistance in fish

Probiogenomic insights into Bacillus velezensis MFSS1 for controlling aquaculture pathogens

Bacillus velezensis MFSS1 (previously known as B. subtilis FS6) was reported to have good probiotic criteria and antibacterial activity against Vibrio spp. and Aeromonas spp., through phenotypic analysis. However, whole genome sequencing is required for commercialising a new probiotic, especially due to reports on probiotics that can cause horizontal gene transfer towards the host microbiome. Therefore, this study aims to investigate the comprehensive genomic characteristics of B. velezensis MFSS1, focusing on its antimicrobial genes against aquaculture pathogens, its probiotic traits, and safety assessment. The bacterial genome was sequenced using Oxford Nanopore sequencing, resulting in 7 contigs with a total length of 3,914,361 base pairs and an average G + C content of 46.58 %. The analysis using ContEst16S and average nucleotide identity revealed that the bacterium previously reported as B. subtilis is actually B. velezensis. Additionally, secondary metabolites against pathogens were predicted using the antiSMASH website, which identified eight secondary metabolites: Bacillibactin, Bacilysin, Surfactin, Difficidin, Fengycin, Bacillaene, Macrolactin H, and Plantazolicin. Furthermore, several probiotic markers were detected, functioning in acid tolerance, bile salt tolerance, adhesion, osmotic stress, and intestinal persistence during the delivery of the bacteria to the host. Interestingly, the in silico safety assessment of the bacterium revealed a lack of 96 antibiotic resistance genes and confirmed it as non-pathogenic to humans, compared with genomic bacteria from ATCC. The study indicates that B. velezensis MFSS1 is a good probiotic through genomic analysis and can be commercialised to control aquaculture pathogens and reduce reliance on antibiotics.

Lactobacillus plantarum ameliorates stress caused by Pseudomonas aeruginosa infection in Nile tilapia

Pseudomonas aeruginosa is a highly pathogenic bacterium affecting the health of Nile tilapia and its production. Fifty moribund fish were collected from farms with high mortality. The causative agent was identified to be P. aeruginosa, and the median lethal dose (LD50) was found to be 1.44 × 105 CFU/mL at a water temperature of 26.5 ± 1.2 °C. To enhance fish immunity, one hundred and thirty-five healthy Nile tilapia were divided into three groups: control (basal diet), single dose of dietary Lactobacillus plantarum at dose of 1 × 1012 CFU/kg feed, and double dose 2 × 1012 CFU/kg feed, where supplemented fish showed significant enhancements of their growth performance, feed utilization, and innate immunity (up-regulating serum antibacterial activity, oxidative burst activity, and phagocytosis). Before infection, the gene expression of interleukin (IL)-1β and tumor necrosis factor (TNF)-α was slightly increased in the head kidney tissue of fish that received dietary L. plantarum, regardless of supplementation dose. Meanwhile, post P. aeruginosa infection, the expression of IL-1β and TNF-α was up-regulated significantly compared to the control. Post-infection, fish supplemented with dietary L. plantarum had a lower mortality rate (MR) (50 %) compared to the control (70 %), providing a 28.57 % relative level of protection (RLP). The Nile tilapia, experimentally infected with P. aeruginosa, showed gasping, decreased food apprehension, and loss of escape reflex. The Nile tilapia, experimentally infected with P. aeruginosa, had some drawbacks, such as immunosuppressed status, abnormal behavior reflexes, and a high mortality rate that dietary L. plantarum could mitigate. Thus, Nile tilapia diet should be supplemented with L. plantarum at 1 × 1012 or 2 × 1012 CFU/kg feed.

Oral delivery of recombinant outer membrane protein 23-based nanovaccine can minimize Aeromonas hydrophila infection in Oreochromis niloticus

Significant financial losses are incurred annually in commercial aquaculture due to the opportunistic pathogen Aeromonas hydrophila outbreaks in warm-water fish species. Thus, an appropriate vaccine and an efficient delivery system must be developed to combat such infectious diseases effectively. This study focused on developing an outer membrane protein (OMPs)-based nanovaccine employing the double emulsion method, integrating it in a biodegradable polylactic-co-glycolic acid (PLGA) polymer. The resultant nanoparticle, carrying the recombinant protein Omp23 (rOmp23), had a size of 346.5nm, an impressive 74.45 % encapsulation efficiency, and a polydispersity index of 0.318. Additionally, the spherical shape of the PLGA-Omp23 nanoparticles was confirmed by scanning electron microscope. Further, to evaluate their in vivo efficacy, tilapia fish were administered the vaccine-incorporated feed orally for 21 days post-challenge with the target pathogen. Cytokine expression levels were monitored at intervals to track the activation of targeted immune genes and to assess nonspecific immune response parameters. The obtained relative percentage survival of 73%, highlighted the therapeutic promise of the PLGA-encapsulated OMP-based nanovaccine. This study demonstrates the utility of nanoparticle system designed to encapsulate the outer membrane protein as a potential oral fish vaccine for infectious diseases. This strategy could be an efficient, cost-effective, and least stressful mode of vaccination to manage infectious diseases.

Comprehensive integration strategy combining chemical modification and physical processing for the efficient formulation of cottonseed protein-derived fish feeds with superior animal husbandry potential

Growing concerns over antibiotic resistance in animal production highlight bayberry tannin (BT), a bioactive polyphenol, as a promising alternative. Cottonseed protein concentrate (CPC), a premium plant-based protein with exceptional functional versatility, holds significant potential for animal feed applications. Herein, innovative C@B complexes, comprising CPC, BT, hydrogen peroxide, and ascorbic acid, were developed through a safe protein-polyphenol grafting modification technique, and followed by an efficient co-extrusion process. The C@B complexes maintained CPC's nutritional profile while forming a porous foam structure. At a 1.00 mg/mL concentration, C@B-100 demonstrated potent antioxidant activity, scavenging 97.14 % of ABTS and 83.59 % of DPPH radicals. In vitro and in vivo experiments revealed that C@B-100 effectively inhibited S. aureus and E. coli growth while exhibiting excellent biocompatibility. Notably, Feed S3 significantly enhanced largemouth bass feed intake, likely due to protein swelling enhancing odor and palatability. Besides, largemouth bass administered with Feed S3 demonstrated marked improvements in antioxidant responses, as evidenced by a significant reduction in reactive oxygen species levels in both plasma and liver, decreasing from 55.82 and 119.47 IU/mL to 46.12 and 77.73 IU/mL, respectively (P < 0.05), while total antioxidant capacity significantly increased from 0.29 and 0.16 U/mgprot to 0.40 and 0.24 U/mgprot, respectively (P < 0.05). Overall, this research underscores the prospects of combining chemical modification and physical processing for the high-value utilization of natural proteins.

Harnessing the fish gut microbiome and immune system to enhance disease resistance in aquaculture

The increasing global reliance on aquaculture is challenged by disease outbreaks, exacerbated by antibiotic resistance, and environmental stressors. Traditional strategies, such as antibiotic treatments and chemical interventions, are becoming less effective, necessitating a shift toward microbiota-based disease control. The fish gut microbiome is a key determinant of immune homeostasis and pathogen resistance. However, previous reviews lack integration of microbiome engineering, machine learning, and next-generation sequencing in fish health strategies. This review encompasses recent advancements in microbiome research, including dietary strategies such as prebiotics, probiotics, synbiotics, and phytogenic feed additives. It synthesizes the latest metagenomic insights, microbiota modulation techniques, and AI-driven disease prediction models. It presents a novel conceptual framework for disease control using microbiome-based approaches in aquaculture. Additionally, we explore emerging methodologies, including microbiota transplantation and synthetic probiotics, to develop precision microbiome interventions. By bridging existing knowledge gaps, this review provides actionable insights into sustainable aquaculture practices through microbiome-driven disease resistance.

Necrophages and necrophiles: a review of their antibacterial defenses and biotechnological potential

With antibiotic resistance on the rise, there is an urgent need for new antibacterial drugs and products to treat or prevent infection. Many such products in current use, for example human and veterinary antibiotics and antimicrobial food preservatives, were discovered and developed from nature. Natural selection acts on all living organisms and the presence of bacterial competitors or pathogens in an environment can favor the evolution of antibacterial adaptations. In this review, we ask if vultures, blow flies and other carrion users might be a good starting point for antibacterial discovery based on the selection pressure they are under from bacterial disease. Dietary details are catalogued for over 600 of these species, bacterial pathogens associated with the diets are described, and an overview of the antibacterial defenses contributing to disease protection is given. Biotechnological applications for these defenses are then discussed, together with challenges facing developers and possible solutions. Examples include use of (a) the antimicrobial peptide (AMP) gene sarcotoxin IA to improve crop resistance to bacterial disease, (b) peptide antibiotics such as serrawettin W2 as antibacterial drug leads, (c) lectins for targeted drug delivery, (d) bioconversion-generated chitin as an antibacterial biomaterial, (e) bacteriocins as antibacterial food preservatives and (f) mutualistic microbiota bacteria as alternatives to antibiotics in animal feed. We show that carrion users encounter a diverse range of bacterial pathogens through their diets and interactions, have evolved many antibacterial defenses, and are a promising source of genes, molecules, and microbes for medical, agricultural, and food industry product development.

From nutrient bioavailability to disease resistance: The comprehensive benefits of chelated minerals in aquaculture

The integration of chelated minerals into aquaculture diets represents a significant advancement in enhancing the health and productivity of aquatic species. These minerals improve nutrient bioavailability, boost immune responses, and increase disease resistance in fish and shrimp, effectively addressing key challenges in aquaculture sustainability. This review highlights the benefits of chelated minerals, including their role in improving feed efficiency, promoting resilience against infections, and mitigating heavy metal toxicity. Key findings indicate that chelated minerals enhance nutrient absorption, which is crucial for optimizing growth and overall health. Furthermore, they strengthen immune responses, thereby increasing resilience to diseases in aquaculture environments. Additionally, these minerals boost antioxidant capacity, helping to alleviate oxidative stress caused by environmental factors and pathogens. The review emphasizes the need for further research to optimize the use of chelated minerals, focusing on mechanisms of action, species-specific responses, and long-term impacts on ecosystems. Successful implementation will require collaboration among researchers, nutritionists, and practitioners to develop evidence-based guidelines for their responsible use. In conclusion, the incorporation of chelated minerals into aquaculture diets has the potential to revolutionize practices and significantly improve the welfare of aquatic species.

Bacillus velezensis FiA2 as an Oxydifficidin-Producing Strain and its Effects on the Growth Performance, Immunity, Intestinal Microbiota, and Resistance to Aeromonas salmonicida Infection in Carassius carassius

In aquaculture, biological control of bacterial infections is a promising strategy that, aside from preventing infections, also benefits the host in several ways. In this study, a Bacillus strain FiA2 isolated from the gut of Carassius carassius (crucian carp) exhibited broad spectrums of activity against multiple aquatic bacterial pathogens. The compound with antibacterial activity was successfully separated and identified as oxydifficidin, with a m/z of 559.47. The oxydifficidin retained its activity even after being exposed to high temperatures, ultraviolet light, proteolytic enzymes, chemical reagents, and alkaline and acidic pH. Furthermore, crucian carp, when supplemented with FiA2 in diet, reduced the infection rate (post-challenged survival rate of 45%), increased the total weight gain by 15.87%, and upregulated the mRNA levels of IGF-1 and IGF-2 (P < 0.05) of muscular tissues. Similarly, the innate immune-related genes in the liver, the spleen, and the head kidney of the fish in the FiA2-supplemented group were significantly upregulated (P < 0.05). In addition, FiA2 modulated the intestinal microbiota, as observed in the FiA2 group of crucian carp; the predominant phyla were Actinobacteriota and Firmicutes, whereas in the control group, Plesiomonas dominated at the genus level. Overall, we conclude that B. velezensis FiA2, a broad-spectrum oxydifficidin-producing strain, resists infection and positively regulates the growth, immunity, and intestinal microbiota of crucian carp and thus can be implemented as a novel probiotic strain for aquaculture.

Dietary Plant-Based Mixture Improves Feed Efficiency, Gross Profit, Physiological Performance, Gene Expression and Gut Health of Nile Tilapia (Oreochromis niloticus)

The goal of this study was to evaluate the effect of the supplemental plant-based blend Phyto AquaNity (PAN) on growth, profitability and health status of Nile tilapia (O. niloticus) cultured in hapas. Juvenile fish of average weight 73 g were stocked in 2-m3 hapas in triplicates at a density of 20 fish m-3 (40 fish hapa-1). Four extruded diets were formulated following isonitrogenous (30% CP), isoenergetic (17 MJ kg-1) standards, with incorporation levels of 0, 0.25, 0.50, or 1.00 g of PAN kg-1 diet. Fish were fed the experimental diets at a daily rate of 2-3% of their body weight (BW) over 80 days. From this study, results showed that growth performance and tissue composition were not significantly impacted by these treatments. Feed intake exhibited a significant reduction while feed efficiency was improved in the groups fed 0.5 g kg-1. Diets supplemented with PAN were also more profitable than the control diet, with 0.5 g kg-1 indicating the highest return (9.24% increase). Digestive enzyme activity and hepatic enzyme activity were significantly improved with an increase in the level of PAN up to 0.50 g kg-1. In addition, immune parameters (lysozyme activity, alternative complement and phagocytic cells) and antioxidant enzymes (superoxide dismutase, glutathione peroxidase and catalase) were significantly enhanced with increasing PAN level up to 0.5 g kg-1 (p < 0.05). Gene expression of cytokines was also upregulated in fish fed with PAN at levels of up to 0.5 g kg-1 (p < 0.05). Moreover, the results showed that higher levels of PAN promoted the growth of beneficial bacteria while reducing the load of pathogenic bacteria. Additionally, intestinal fold length and goblet cell count were significantly increased in the group fed PAN up to 0.5 g kg-1. A quadratic regression analyses performed on feed efficiency, profitability, hepatic enzyme activity and gut microbial load revealed that 0.60-0.65 g kg-1 of feed were the optimal dosages. Regarding immunological and antioxidant responses, the optimal dosages ranged between 0.75 and 0.85 g kg-1. Overall, about 0.60-0.85 g PAN kg-1 feed is suggested for optimum performance, profitability, gut health and overall health status of Nile tilapia, depending on the target objective for which this product is added.

Effects of Bacillus coagulans on Growth Performance, Digestive Enzyme Activity, and Intestinal Microbiota of the Juvenile Fourfinger Threadfin (Eleutheronema tetradactylum)

The effects of Bacillus coagulans (BC) T-21 on growth performance, intestinal digestive enzyme activity, intestinal morphology, and intestinal microbiota of juvenile fourfinger threadfin (Eleutheronema tetradactylum) were investigated in the present study. Healthy juvenile E. tetradactylum with an initial body weight of 4.2 ± 0.5 g were fed a basal diet sprayed with 1 × 108 cfu/g B. coagulans for eight weeks, and the growth parameters, intestinal digestive enzyme activities, HE-stained intestinal sections, and intestinal microbiota of the juvenile fish were measured. The differences in the feed conversion ratio between the experimental and control groups (fed the basal diet) were extremely significant (p < 0.01), whereas the differences in weight gain rate, specific growth rate, survival rate, and condition factor were significant (p < 0.05). In the experimental group, trypsin and amylase activities decreased significantly, whereas there were no significant differences in lipase activity between the two groups. Compared to the control group, the height of the intestinal villi was greater. No significant differences were observed in the diversity of intestinal microbiota and microbial species at the genus level (p > 0.05). Based on the function prediction analysis, the count values for the glycan biosynthesis, metabolism, and digestive system pathways were significantly increased in the experimental group (p < 0.05). However, there were no significant differences in the counts of other functional pathways (p > 0.05). These results indicate that dietary B. coagulans supplementation is effective in promoting the growth performance and intestinal health of juvenile E. tetradactylum.

New advances in biological preservation technology for aquatic products

Aquatic products, characterized by their high moisture content, abundant nutrients, and neutral pH, create an optimal environment for the rapid proliferation of spoilage organisms, lipid oxidation, and autolytic degradation. These factors collectively expedite the spoilage and deterioration of aquatic products during storage and transportation within the supply chain. To maintain the quality and extend the shelf-life of aquatic products, appropriate preservation methods must be implemented. The growing consumer preference for bio-preservatives, is primarily driven by consumer demands for naturalness and concerns about environmental sustainability. The present review discusses commonly employed bio-preservatives derived from plants, animals, and microorganisms and their utilization in the preservation of aquatic products. Moreover, the preservation mechanisms of bio-preservatives, including antioxidant activity, inhibition of spoilage bacteria and enzyme activity, and the formation of protective films are reviewed. Integration of bio-preservation techniques with other methods, such as nanotechnology, ozone technology, and coating technology that enhance the fresh-keeping effect are discussed. Importantly, the principal issues in the application of bio-preservation technology for aquatic products and their countermeasures are presented. Further studies and the identification of new bio-preservatives that preserve the safety and quality of aquatic products should continue.

Essential Oil of Bay Laurel (Laurus nobilis) Enhances Growth and Immunity in Cold-Stressed Nile Tilapia (Oreochromis Niloticus)

Bay laurel (Laurus nobilis) essential oil is known for its antimicrobial, anti-inflammatory, and antioxidant properties. This study examined the effects of L. nobilis oil (LN) on Nile tilapia (Oreochromis niloticus) under cold stress conditions (16°C). Tilapia (initial weight, 5.02 ± 0.02 g) were acclimatized to 16°C for 14 days before being fed diets containing 0, 0.5, 1.0, 1.5, 2.0, and 2.5 g/kg LN oil for 84 days. The 1.5 g/kg LN oil group exhibited the highest final body weight and weight gain (p ≤ 0.05), while survival rates peaked at 1 g/kg. Biometric indices and feed efficiency were significantly enhanced, particularly at 1.5 g/kg (p ≤ 0.05). Histological analysis revealed improved intestinal and hepatic structures in LN-supplemented groups, although mild alterations were observed at 2.0 and 2.5 g/kg. Blood biochemical analysis showed increased total protein and reduced cholesterol in supplemented groups. Immune responses, including serum lysozyme activity and bacterial inhibition, were significantly enhanced at 1.5 g/kg or higher (p ≤ 0.05). Antioxidant enzyme activities, including superoxide dismutase (SOD) and catalase (CAT), increased (p ≤ 0.05) with LN oil supplementation, while malondialdehyde (MDA) levels decreased, indicating reduced oxidative stress. Gene expression analysis demonstrated increased insulin-like growth factor 1 and glucose transporter 4 levels with 1.5 g/kg LN oil, and tumor necrosis factor-alpha expression decreased at higher dosages. Dietary LN oil, particularly at 1.5 g/kg, enhances growth, immunity, and antioxidant defense in Nile tilapia under cold stress. Future studies should optimize dosages and explore broader applications across species and conditions.

Data on zinc chelates of glycine as a growth and survival enhancer in hybrid grouper and whiteleg shrimp

The dataset demonstrates the efficacy of Aqua Ectogon-284, a zinc chelates of glycine, as a dietary supplement to enhance growth and survival in hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) and whiteleg shrimp (Penaeus vannamei). Two concentrations (1g/kg feed and 2g/kg feed) were evaluated against a control group to identify an optimal dosage that maximizes growth and health outcomes. Both the species exhibited improved growth performance and survival rates with dietary supplementation. The hybrid grouper fed a 1g/kg diet achieved the highest final weight of 100.00 g, with significant increases in length and survival rates of 96.00%. Similarly, whiteleg shrimp demonstrated enhanced final weights and survival (94.67%) with the same treatment. These findings revealed that zinc chelate glycine increased the growth rate and reduced mortality in farmed species.

Isolation, characterization of Bacillus subtilis and Bacillus amyloliquefaciens and validation of the potential probiotic efficacy on growth, immunity, and gut microbiota in hybrid sturgeon (Acipenser baerii ♀ × Acipenser schrenckii ♂)

Probiotics are increasingly considered as an alternative to antibiotics in developing environmentally sustainable aquaculture practices. Hybrid sturgeon (Acipenser baerii ♀ × Acipenser schrenckii ♂), a globally popular species valued for its nutritional content and caviar, has limited research on host-associated probiotics. In this study, we isolated and identified Bacillus subtilis and Bacillus amyloliquefaciens from healthy hybrid sturgeon and assessed their impact on growth, immunity, gut microbiota, and transcriptome following an 8-week feeding trial. The isolated strains demonstrated strong production of protease, amylase, lipase, and cellulase, along with broad-spectrum pathogen inhibition, including Aeromonas veronii, Aeromonas sobria, and Yersinia ruckeri. Supplementation with B. subtilis and B. amyloliquefaciens significantly improved growth performance and increased survival rates against A. veronii infection. Mechanistically, probiotics altered gut microbiota composition, enhancing digestive functions. Transcriptome analysis further revealed that probiotic supplementation boosted immune response and protein digestion and absorption. These findings suggest that B. subtilis and B. amyloliquefaciens are promising probiotic candidates for the hybrid sturgeon industry, offering effective protection against A. veronii infection.

Promising Probiotic Candidates for Sustainable Aquaculture: An Updated Review

With the intensification of aquaculture to meet the rising demands of fish and shellfish, disease outbreaks during the larval and adult stages are a major challenge faced by aqua culturists. As the prophylactic use of vaccines and antibiotics has several limitations, research is now focused on sustainable alternatives to vaccines and antibiotics, e.g., medicinal plants, probiotics, postbiotics, prebiotics, and synbiotics, as promising candidates to strengthen the immune response of fish and shellfish and to control disease outbreaks. With respect to probiotics, numerous studies are available revealing their health-promoting and beneficial impacts in aquaculture. However, most studies focus on Bacillus and Lactobacillus species. Keeping in view the positive effects of probiotic lactic acid bacteria in aquaculture, researchers are now looking for other probiotic bacteria that can be used in aquaculture. Recently, many non-lactic acid bacteria (non-LAB), which are mainly host-associated, have been reported to reveal beneficial effects in fish and shellfish aquaculture. The main non-LAB probiotic genera are Bifidobacterium, Clostridium, Microbacterium, Micrococcus, Paenibacillus, Acinetobacter, Alcaligenes, Enterobacter, Phaeobacter Pseudoalteromonas, Pseudomonas, Pseudomonas, and Vibrio. Despite the promising effects of non-LAB probiotics, comparably, there is limited available information in this context. This review focuses only on probiotic strains that are non-LAB, mostly isolated from the host digestive tract or rearing water, and discusses their beneficial effects in fish and shellfish aquaculture. This review will provide detailed information on the use of various non-LAB bacteria and provide a roadmap to future studies on new probiotics for sustainable aquaculture.

Single-strain probiotics enhance growth, anti-pathogen immunity, and resistance to Nocardia seriolae in grey mullet (Mugil cephalus) via gut microbiota modulation

Grey mullet (Mugil cephalus) aquaculture is economically vital due to the high value of its roe. However, it faces significant risks from disease outbreaks, particularly from Nocardia seriolae. Current reliance on antibiotics has drawbacks, highlighting the potential of probiotics as a promising alternative. Despite this, no studies have focused on the effects and mechanisms of probiotics in disease prevention and treatment in grey mullet. This study, therefore, investigates the efficacy of probiotics in enhancing disease resistance and promoting growth in grey mullet. Three strains of probiotics, Lacticaseibacillus rhamnosus FS3051, Limosilactobacillus reuteri FS3052, and Bacillus subtilis natto NTU-18, were selected to evaluate their anti-N. seriolae activity and hydrolytic enzyme secretion in vitro. Then, 144 grey mullet were randomly divided into four groups: control, L. rhamnosus FS3051, L. reuteri FS3052, and B. subtilis natto NTU-18. After being fed the corresponding diet for 28 days, fish were measured for immune gene expression and short-term growth followed by challenge of N. seriolae. Survival rates were recorded for 35 days post challenge. Additionally, the gut microbiota of the control and probiotic groups with effects on both growth and protection against N. seriolae were analyzed to investigate the potential role of gut microbiota. Results demonstrated that L. rhamnosus FS3051 and L. reuteri FS3052 inhibited N. seriolae, while B. subtilis natto NTU-18 did not inhibited N. seriolae. Probiotics also had the ability to secrete hydrolytic enzymes. Probiotic-fed grey mullet showed significant improvements in weight gain ratio, feed efficiency, and specific growth rate, particularly in the B. subtilis natto NTU-18 group. Immune gene expression was enhanced by probiotics, especially L. rhamnosus, FS3051, which induced IL-8, IL-1β, TNF-α, IFN-γ, and MHCI. Survival rates post-N. seriolae challenge improved significantly for L. rhamnosus FS3051-fed fish. L. rhamnosus FS3051 also altered the gut microbiota, enriching beneficial genera like Lactobacillus, which correlated positively with immune responses and growth, while reducing Mycoplasma and Rhodobacter, which were negatively correlated with immune responses. This study underscores the potential of probiotics in enhancing disease resistance and growth via regulating gut microbiota in grey mullet.

Probiotic Lactobacillus rhamnosus modulates MCLR-induced oogenesis disorders in zebrafish: Evidence from the transcriptome

Microcystin-LR (MCLR) produced by cyanobacterial blooms have received global attention. MCLR has been recognized as a reproductive toxin to fish and poses a threat to ecosystem stability. It has been proven that probiotic dietary management can improve reproductive performance of fish. It is worth paying attention to exploring whether probiotic management can alleviate the reproductive toxicity caused by MCLR. In this investigation, adult zebrafish were exposed to different doses of MCLR solution (0, 2.2, and 22 μg/L) with or without the Lactobacillus rhamnosus GG supplementation for a duration of 28 days. The results showed that female zebrafish spawning was reduced after exposure to MCLR, but this reduction was reversed when L. rhamnosus GG was added. To elucidate how L. rhamnosus GG mitigates reproductive toxicity caused by MCLR, we examined a series of indicators of MCLR accumulation, ovarian histology, hormones, and transcriptome levels. Our study showed that L. rhamnosus GG could alleviate oogenesis disorders and ultimately attenuate MCLR-induced reproductive toxicity by reducing MCLR accumulation in the gonads, modulating the expression of endocrine system and auto/paracrine factors. The transcriptome results revealed that single or combined exposure of MCLR and L. rhamnosus GG mainly affected the endocrine system, energy metabolism, and RNA degradation and translation. Overall, our results provide new insights for alleviating MCLR-induced reproductive toxicity and help promote healthy aquaculture.

Probiotics Enhance Coilia nasus Growth Performance and Nutritional Value by Regulating Glucolipid Metabolism via the Gut-Liver Axis

Large-scale intensive feeding triggered reduced growth performance and nutritional value. Exogenous probiotics can promote the growth performance and nutritional value of fish through improving the intestinal microbiota. However, detailed research on the correlation between the intestinal microbiota, growth performance, and nutritional value remains to be elucidated. Therefore, we performed metagenomic and metabolomic analysis to investigate the effects of probiotic addition to basal diet (1.0 × 108 CFU/g) (PF) and water (1.0 × 108 CFU/g) (PW) on the growth performance, muscle nutritional value, intestinal microbiota and their metabolites, and glucolipid metabolism in Coilia nasus. The results showed that FBW, BL, and SGR were enhanced in PF and PW groups. The concentrations of EAAs, TAAs, SFAs, MUFAs, and PUFAs were increased in PF and PW groups. Metagenomic and metabolic analyses revealed that bacterial community structure and metabolism were changed in the PF and PW groups. Moreover, adding probiotics to diet and water increased SCFAs and bile acids in the intestine. The gene expression associated with lipolysis and oxidation (hsl, pparα, cpt1, and acadm) and glycolysis (gck and pfk) was upregulated, while the gene expression associated with lipid synthesis (srebp1, acc, dgat, and elovl6) and gluconeogenesis (g6pca1, g6pca2, and pck) was downregulated in the liver. Correlation analysis displayed that hepatic glucolipid metabolism was regulated through the microbiota-gut-liver axis. Mantel test analysis showed that growth performance and muscle nutritional value were improved by the gut-liver axis. Our findings offered novel insights into the mechanisms that underlie the enhancement of growth performance and nutritional value in C. nasus and other fish by adding probiotics.

Safety Assessment of Camelid-Derived Single-Domain Antibody as Feed Additive for Juvenile Whiteleg Shrimp (Litopenaeus vannamei) Against White Spot Syndrome Virus

A six-week feeding trial was conducted to assess the safety of single-domain antibodies (sdAbs) derived from camelids against the white spot syndrome virus (WSSV) (WSSVvp28 was used as the antigen), focusing on the whole-organism responses and molecular-level changes in juvenile whiteleg shrimp (Litopenaeus vannamei). Five experimental diets with varying levels of sdAbs were formulated: CON (no sdAb supplementation); SDA8.2 (8.20% of sdAbs); SDA16.4 (16.40% of sdAbs); SDA24.6 (24.60% of sdAbs); and SDA32.8 (32.80% of sdAbs). In the CON diet, 450 mL of water per kg of diet (45%) was used to form a feed dough, while sdAbs were used to replace the water in the treatment diets. A total of 450 shrimp, with an initial body weight of 3.27 ± 0.02 g (mean ± SEM), were randomly distributed in 15 tanks (30 shrimp per tank; three tanks per treatment). Each tank was filled with 30 L of seawater (77 L capacity) in an indoor semi-recirculating system with a constant water flow rate of 1.2 L min-1. The photoperiod was maintained at 12 h of light and 12 h of dark. The water temperature, pH, salinity, and dissolved oxygen were 27.3 ± 0.1 °C, 7.61 ± 0.01, 34 ± 1 ppt, and 5.94 ± 0.04 mg L-1, respectively. During the feeding trial, the shrimp were fed the experimental diet (40% protein and 11% lipid) three times a day for six weeks. Following the feeding trial, an acute cold-water-temperature stress test was conducted by abruptly exposing the shrimp from each treatment to 15 °C for 4 h, down from 27 °C. The results showed no significant differences in the growth performance (weight gain, feed utilization efficiency, survival, etc.), plasma metabolites (aspartate aminotransferase activity, alanine aminotransferase activity, total protein, and glucose), or antioxidant enzymes (superoxide dismutase and glutathione peroxidase) among all the experimental diets (p > 0.05). In the acute cold-temperature stress test, there was no significant interaction between sdAb supplementation and temperature stress, nor any main effect from either factor, except for the main effect of temperature stress on the glucose levels, which was significantly higher in shrimp exposed to cold-temperature stress (p < 0.05). The next-generation sequencing of differentially expressed genes (DEGs) in the hepatopancreases of shrimp fed the CON, SDA16.4, and SDA32.8 diets, followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, indicated that DEGs were significantly enriched in signaling pathways associated with growth, cold stress, and antioxidant systems. Overall, the results from conventional measurements suggest that the use of sdAbs against the WSSV may be safe for juvenile whiteleg shrimp. However, findings from the sophisticated analysis indicate that further research is needed to understand the molecular mechanisms underlying the observed changes, and to evaluate the long-term effects of sdAb supplementation in shrimp diets.

Factors Affecting Yeast Digestibility and Immunostimulation in Aquatic Animals

The aquafeed industry increasingly relies on using sustainable and appropriate protein sources to ensure the long-term sustainability and financial viability of intensive aquaculture. Yeast has emerged as a viable substitute protein source in the aquaculture sector due to its potential as a nutritional supplement. A substantial body of evidence exists to suggest that yeast has the potential to act as an effective immune-stimulating agent for a range of aquaculture fish species. Furthermore, the incorporation of yeast supplements and feed additives has the potential to bolster disease prevention, development, and production within the aquaculture sector. Except for methionine, lysine, arginine, and phenylalanine, which are typically the limiting essential amino acids in various fish species, the various yeast species exhibit amino acid profiles that are advantageous when compared to fishmeal. The present review considers the potential nutritional suitability of several yeast species for fish, with particular attention to the various applications of yeast in aquaculture nutrition. The findings of this study indicate that the inclusion of yeast in the diet resulted in the most favorable outcomes, with improvements observed in the overall health, growth performance, and nutritional condition of the fish. Digestibility, a key factor in sustainable feed development, is discussed in special detail. Additionally, this review addresses the utilization of yeast as an immunostimulating agent for fish and its digestion in fish. Furthermore, the research emphasizes the necessity of large-scale production of yeast as a substitute for fishmeal in aquaculture.

Synbiotic effects of Lactobacillus plantarum CMT1 and Morinda citrifolia on the growth performance and disease resistance of whiteleg shrimp

This study assesses the effects of a prebiotic derived from Morinda citrifolia (noni fruit) extract and a probiotic of Lactobacillus plantarum CMT1 alone and in combination on the survival, growth performance, digestive enzymes, and disease resistance of whiteleg shrimp. A total of 1200 juvenile shrimp were randomly allocated to four treatments: control (not supplemented with noni fruit extract or L. plantarum CMT1), Treatment 1 (TRT1) (supplemented with 1 % noni fruit extract), Treatment 2 (TRT2) (supplemented with 108 CFU/kg L. plantarum CMT1), and Treatment 3 (TRT3) (supplemented with 1 % noni fruit extract and 108 CFU/kg L. plantarum CMT1). After 56 days of feeding, the growth indices of the TRT3 group were statistically larger than the other treatments (P < 0.05). Shrimp in the three treatment groups demonstrated significantly enhanced survival compared to those in the control group (P < 0.05), but no significant differences were observed among these three groups (P > 0.05). Shrimp fed the TRT3 diet had the lowest feed conversion rate, which was statistically significant compared to the other groups. Shrimp in the TRT3 group also had significantly higher amylase and protease levels than the control group. In addition, the use of fruit extract or L.plantarum CMT1 alone and in combination significantly increased shrimp survival after exposure to Vibrio parahaemolyticus, with the TRT3 group recording the highest value. The results indicate that a synbiotic of M. citrifolia extract and L.plantarum CMT1 could be used in shrimp aquaculture to promote animal development and health.

The Potential of Fish Protein Hydrolysate Supplementation in Nile Tilapia Diets: Effects on Growth and Health Performance, Disease Resistance, and Farm Economic Analysis

Fish protein hydrolysate (FPH) has shown immense potential as a dietary protein supplement and immunostimulant in aquaculture, especially in Nile tilapia production. Four isoproteic diets (30% crude protein) were prepared by including FPH at varying percentages (0%, 0.5%, 1%, and 2%). Nile tilapia fed with FPH diets for 90 days, and their growth performance, feed utilization, blood biochemistry, liver and gut morphology, and resistance against Streptococcus iniae were investigated. The findings revealed that diets physical attributes such as pellet durability index and water stability were remarkably (p < 0.05) varied between experimental diet groups. Furthermore, the test diets were more palatable when FPH was included at 1% and 2%. Fish that were fed with a 2% FPH-treated diet had significantly (p < 0.05) greater growth indices than other treatments. Additionally, their feed utilization was significantly (p < 0.05) improved. The experimental diets and intestinal total bacteria count (TBC) exhibited a rising trend with FPH levels, where the 2% FPH-treated diet recorded the highest TBC. Neutrophil (109/L), lymphocyte (109/L), eosinophil (109/L), and red blood cell(1012/L) counts were significantly (p < 0.05) higher in the 2% FPH-treated group, while the white blood cell (109/L), and basophil (109/L) counts were not influenced by the FPH inclusion. Moreover, the FPH-treated groups displayed lower creatinine, bilirubin, and urea levels than the control. The histological examination demonstrated that themid-intestine of 2% FPH-fed Nile tilapia had an unbroken epithelial wall, more villi with frequent distribution of goblet cells, wider tunica muscularis, and stronger stratum compactum bonding than other treatments. Additionally, this group exhibited more nuclei and erythrocytes and less vacuolar cytoplasm in liver than their counterparts. Nile tilapia that were given a diet containing 2% FPH had significantly (p < 0.05) higher resistance (83.33%) to S. iniae during the bacterial challenge test. A significant (p < 0.05) enhancement in farm economic efficiency was observed in the higher inclusion of FPH in diets. In summary, 2% FPH supplementation in Nile tilapia diets improved their growth performance, feed utilization, health status, disease resistance, and farm economic efficiency.

Lactococcus lactis MA5 is a potential autochthonous probiotic for nutrient digestibility enhancement and bacterial pathogen inhibition in hybrid catfish (Ictalurus punctatus × I. furcatus)

With the emergence of diseases, the U.S. catfish industry is under challenge. Current trends prefer autochthonous bacteria as potential probiotic candidates owing to their adaptability and capacity to effectively colonize the host's intestine, which can enhance production performance and bolster disease resistance. The objective of this study was to isolate an autochthonous bacterium as probiotic for hybrid catfish. Initially, an analysis of the intestinal microbiota of hybrid catfish reared in earthen ponds was conducted for subsequent probiotic development. Twenty lactic acid bacteria were isolated from the digesta of overperforming catfish, and most of the candidates demonstrated probiotic traits, including proteolytic and lipolytic abilities; antagonistic inhibition of catfish enteric bacterial pathogens, negative haemolytic activity and antibiotic susceptibility. Subsequent to this screening process, an isolate of Lactococcus lactis (MA5) was deemed the most promising probiotic candidate. In silico analyses were conducted, and several potential probiotic functions were predicted, including essential amino acids and vitamin synthesis. Moreover, genes for three bacteriocins, lactococcin A, enterolysin A and sactipeptide BmbF, were identified. Lastly, various protectant media for lyophilization of MA5 were assessed. These findings suggest that Lactococcus lactis MA5 can be an autochthonous probiotic from hybrid catfish, holding promise to be further tested in feeding trials.

Effects of passion fruit peel (Passiflora edulis) pectin and red yeast (Sporodiobolus pararoseus) cells on growth, immunity, intestinal morphology, gene expression, and gut microbiota in Nile tilapia (Oreochromis niloticus)

This study explores the effects of dietary supplementation with passion fruit peel pectin (Passiflora edulis) and red yeast cell walls (Sporidiobolus pararoseus) on growth performance, immunity, intestinal morphology, gene expression, and gut microbiota of Nile tilapia (Oreochromis niloticus). Nile tilapia with an initial body weight of approximately 15 ± 0.06 g were fed four isonitrogenous (29.09-29.94%), isolipidic (3.01-4.28%), and isoenergetic (4119-4214 Cal/g) diets containing 0 g kg-1 pectin or red yeast cell walls (T1 - Control), 10 g kg-1 pectin (T2), 10 g kg-1 red yeast (T3), and a combination of 10 g kg-1 pectin and 10 g kg-1 red yeast (T4) for 8 weeks. Growth rates and immune responses were assessed at 4 and 8 weeks, while histology, relative immune and antioxidant gene expression, and gut microbiota analysis were conducted after 8 weeks of feeding. The results showed that the combined supplementation (T4) significantly enhanced growth performance metrics, including final weight, weight gain, specific growth rate, and feed conversion ratio, particularly by week 8, compared to T1, T2, and T3 (P < 0.05). Immunological assessments revealed increased lysozyme and peroxidase activities in both skin mucus and serum, with the T4 group showing the most pronounced improvements. Additionally, antioxidant and immune-related gene expression, including glutathione peroxidase (GPX), glutathione reductase (GSR), and interleukin-1 (IL1), were upregulated in the gut, while intestinal morphology exhibited improved villus height and width. Gut microbiota analysis indicated increased alpha and beta diversity, with a notable rise in beneficial phyla such as Actinobacteriota and Firmicutes in the supplemented groups. These findings suggest that the combined use of pectin and red yeast cell walls as prebiotics in aquaculture can enhance the health and growth of Nile tilapia, offering a promising alternative to traditional practices. Further research is needed to determine optimal dosages for maximizing these benefits.

The Indigenous Probiotic Lactococcus lactis PH3-05 Enhances the Growth, Digestive Physiology, and Gut Microbiota of the Tropical Gar (Atractosteus tropicus) Larvae

Probiotics in aquaculture hold promise for enhancing fish health and growth. Due to their increased specificity and affinity for their host, indigenous probiotics may offer isolated and potentially amplified benefits. This study investigated the effects of Lactococcus lactis PH3-05, previously isolated from adults of tropical gar (Atractosteus tropicus), on the growth, survival, digestive enzyme activity, intestinal morphology, expression of barrier and immune genes, and intestinal microbiota composition in the larvae of tropical gar. Larvae were fed with live L. lactis PH3-05 concentrations of 104, 106, and 108 CFU/g for 15 days alongside a control diet without probiotics. Higher concentrations of L. lactis PH3-05 (106 and 108 CFU/g) positively influenced larval growth, increasing hepatocyte area and enterocyte height. The 106 CFU/g dose significantly enhanced survival (46%) and digestive enzyme activity. Notably, the 108 CFU/g dose stimulated increased expression of muc-2 and il-10 genes, suggesting enhanced mucosal barrier function and anti-inflammatory response. Although L. lactis PH3-05 did not significantly change the diversity, structure, or Phylum level composition of intestinal microbiota, which was constituted by Proteobacteria, Bacteroidota, Chloroflexi, and Firmicutes, an increase in Lactobacillus abundance was observed in fish fed with 106 CFU/g, suggesting enhanced probiotic colonization. These results demonstrate that administering L. lactis PH3-05 at 106 CFU/g promotes growth, survival, and digestive health in A. tropicus larvae, establishing it as a promising indigenous probiotic candidate for aquaculture applications.

Evaluation of the synbiotic effects of Saccharomyces cerevisiae and mushroom extract on the growth performance, digestive enzyme activity, and immune status of zebrafish danio rerio

BACKGROUND

The quest for candidate probiotics and prebiotics to develop novel synbiotics for sustainable and profitable fish farming remains a major focus for various stakeholders. In this study, we examined the effects of combining two fungal probiotics, Saccharomyces cerevisiae and Aspergillus niger with extracts of Jerusalem artichoke and white button mushroom to develop a synbiotic formulation to improve the growth and health status of zebrafish (Danio rerio). An initial in vitro study determined the most effective synbiotic combination, which was then tested in a 60-day in vivo nutritional trial using zebrafish (80 ± 1.0 mg) as a model animal. Four experimental diets were prepared: a control diet (basal diet), a prebiotic diet with 100% selected mushroom extract, a probiotic diet with 107 CFU of S. cerevisiae/g of diet, and a synbiotic diet with 107 CFU of S. cerevisiae/g of diet and 100% mushroom extract. As readouts, growth performance, survival, digestive enzyme activity and innate immune responses were evaluated.

RESULTS

In vitro results showed that the S. cerevisiae cultured in a medium containing 100% mushroom extract exhibited the maximum specific growth rate and shortest doubling time. In the in vivo test with zebrafish, feeding them with a synbiotic diet, developed with S. cerevisiae and mushroom extract, led to a significant improvement in the growth performance of zebrafish (P < 0.05). The group of zebrafish fed with the synbiotic diet showed significantly higher levels of digestive enzyme activity and immune responses compared to the control group (P < 0.05).

CONCLUSION

Taken together, these results indicated that the combination of S. cerevisiae and mushroom extract forms an effective synbiotic, capable of enhancing growth performance and immune response in zebrafish.

Bioactive compound from marine seagrass Streptomyces argenteolus TMA13: combatting fish pathogens with time-kill kinetics and live-dead cell imaging

Actinobacteria, pervasive in aquatic and terrestrial environments, exhibit a filamentous morphology, possess DNA with a specific G + C content and production of numerous secondary metabolites. This study, focused on actinobacteria isolated from marine seagrass, investigating their antibacterial activity against fish pathogens. Among 28 isolates, Streptomyces argenteolus TMA13 displayed the maximum zone of inhibition against fish pathogens-Aeromonas hydrophila (10 mm), Aeromonas caviae (22 mm), Edwardsiella tarda (17 mm), Vibrio harveyi (22 mm) and Vibrio anguillarum (12 mm) using the agar plug method. Optimization of this potent strain involved with various factors, including pH, temperature, carbon source and salt condition to enhance both yield production and antibacterial efficacy. In anti-biofilm assay shows the maximum percentage of inhibition while increasing concentration of TMA13 extract. Minimal Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) assays with TMA13 crude extract demonstrated potent activity against fish pathogens at remarkably low concentrations. Time-kill kinetics assay showcased growth curve variations over different time intervals for all fish pathogens treated with a 100 µg/ml concentration of crude extract, indicating a decline in cells viability and progression into the death phase. Additionally, fluorescence microscopic visualization of bacterial cells exposed to the extracts emitting green and red fluorescence, enabling live-dead cell differentiation was also studied. Further characterization of the crude extract through GC-MS and FT-IR analyses performed and identified secondary metabolites with functional groups exhibiting significant antibacterial activity. This study elucidates the capacity of Streptomyces argenteolus TMA13 to enhance the production of antibiotic compounds effective against fish pathogens.

Optimizing reproductive performance in pangasius catfish broodstock: A review of dietary and molecular strategies

Pangasius catfish, a significant player in the global whitefish market, encounters challenges in aquaculture production sustainability. Quality broodstock maintenance and seed production are impeded by growth, maturation, and fecundity issues. This review investigates the efficacy of strategic nutrient composition and molecular strategies in enhancing broodstock conditions and reproductive performance across various fish species. A notable knowledge gap for Pangasius catfish hampers aquaculture progress. The review assesses nutrient manipulation's impact on reproductive physiology, emphasizing pangasius broodstock. A systematic review analysis following PRISMA guidelines was conducted to identify research trends and hotspots quantitatively, revealing a focus on P. bocourti and fertilization techniques. Addressing this gap, the review offers insights into dietary nutrients manipulation and genetic tool utilization for improved seed production, contributing to pangasius catfish aquaculture sustainability.

Impact of protectants and the method of preservation on the stability of potentially probiotic bacteria

Probiotics offer health advantages when consumed in adequate quantities. As ongoing research identifies promising new strains, ensuring their viability and functionality through simple preservation methods is vital for success within the probiotic industry. This study employed a factorial design to investigate the combined effects of four cryoprotectants [C1: MRS broth + 14 % (w/v) glycerol, C2: Aqueous solution containing 4 % (w/v) trehalose, 6 % (w/v) skimmed milk, and 4 % (w/v) sodium glutamate, C3: Aqueous solution containing 10 % (w/v) skimmed milk and 4 % (w/v) sodium glutamate, C4: Aqueous solution containing 4 % (w/v) sucrose, 6 % (w/v) skimmed milk, and 4 % (w/v) sodium glutamate] and three methods of preservation (P1: -86 °C freezing, P2: -196 °C liquid nitrogen freezing, and P3: storing at 4 °C after lyophilization) on the cell viability of three potentially probiotic strains over 12 months. Pediococcus sp P15 and Weissella cibaria ml6 had the highest viability under treatments C3 and C2, after 12 months of storage, respectively. Meanwhile, Lactococcus lactis ml3 demonstrated the highest viability in both treatments C2 and C4 (P ≤ 0.05). According to the results freezing, either P1 or P2, is the most effective preservation method for P. sp P15 and W. cibaria ml6. Meanwhile, L. lactis ml3 showed the highest colony count under treatment (P1) after 12 months of storage (P ≤ 0.05). Among the tested conditions, P. sp P15 and L. lactis ml3 exhibited the highest viability and bile salt resistance when stored under P1C1. For W. cibaria ml6, the optimal storage condition was P2C2 (frozen in liquid nitrogen with cryoprotectant C2).

Selenium toxicity in fishes: A current perspective

Anthropogenic activities have led to increased levels of contaminants that pose significant threats to aquatic organisms, particularly fishes. One such contaminant is Selenium (Se), a metalloid which is released by various industrial activities including mining and fossil fuel combustion. Selenium is crucial for various physiological functions, however it can bioaccumulate and become toxic at elevated concentrations. Given that fishes are key predators in aquatic ecosystems and a major protein source for humans, Se accumulation raises considerable ecological and food safety concerns. Selenium induces toxicity at the cellular level by disrupting the balance between reactive oxygen species (ROS) production and antioxidant capacity leading to oxidative damage. Chronic exposure to elevated Se impairs a wide range of critical physiological functions including metabolism, growth and reproduction. Selenium is also a potent teratogen and induces various types of adverse developmental effects in fishes, mainly due to its maternal transfer to the eggs. Moreover, that can persist across generations. Furthermore, Se-induced oxidative stress in the brain is a major driver of its neurotoxicity, which leads to impairment of several ecologically important behaviours in fishes including cognition and memory functions, social preference and interactions, and anxiety response. Our review provides an up-to-date and in-depth analysis of the various adverse physiological effects of Se in fishes, while identifying knowledge gaps that need to be addressed in future research for greater insights into the impact of Se in aquatic ecosystems.

Transcriptome analysis reveals high concentration of resveratrol promotes lipid synthesis and induces apoptosis in Siberian sturgeon (Acipenser baerii)

Resveratrol has been reported to promote immunity and decrease oxidative stress, but which demonstrates biphasic effects relied on the use concentration. In this study, the effects of diet supplement with a relative high concentration of resveratrol (0.32 mg/kg) on metabolism, antioxidation and apoptosis of liver were investigated in Siberian sturgeon. The results showed that resveratrol significantly increased the lipid synthesis and the apoptosis, but did not either activate the antioxidant NRF2/KEAP1 pathway or enhance the antioxidant enzyme activity. Transcriptome analysis revealed significant changes in regulatory pathways related to glycolipid, including PPAR signaling pathway, Insulin signaling pathway, Fatty acid biosynthesis, and Glycolysis/Gluconeogenesis. In addition, resveratrol significantly increased the lipid synthesis genes (accα and fas), fatty acid transport gene (fatp 6) and gluconeogenesis gene (gck), but decreased the survival-promoting genes (gadd45β and igf 1). These findings highlight a significant effect of resveratrol on glycolipid metabolism in Siberian sturgeon. Moreover, this study also demonstrated that 0.32 mg/kg resveratrol has physiological toxicity to the liver of Siberian sturgeon, indicating that this dose is too high for Siberian sturgeon. Thus, our study provides a valuable insight for future research and application of resveratrol in fish.

Host Gut-Derived Probiotic, Exiguobacterium acetylicum G1-33, Improves Growth, Immunity, and Resistance to Vibrio harveyi in Hybrid Grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂)

Several exogenous probiotics are applicable in fish culture; however, challenges in isolation and verification have hindered the full utilization of numerous host probiotics. Therefore, this study aimed to apply the host probiotic Exiguobacterium acetylicum G1-33 to hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) cultures and explore its mechanism of action. In total, 360 hybrid grouper were divided into four groups, which were fed the following for 60 days: three received commercial feed with varying concentrations of E. acetylicum G1-33 (106, 108, and 1010 CFU/g), while a control group received commercial feed. The results showed that supplementation with 106 and 108 CFU/g of E. acetylicum G1-33 enhanced gut morphology, upregulated growth-related genes (ghr1, igf-2, s6k1, tor), and promoted growth, with supplementation with 108 CFU/g resulting in the most notable enhancement. However, supplementation with 1010 CFU/g inhibited growth, possibly because of changes in intestinal morphology. Additionally, supplementation with E. acetylicum G1-33 upregulated the expression of immune-related genes (c3, myd88, Cu/Zn-sod, tlr3, and tnf2) in the liver and head kidney but led to an increase in malondialdehyde content, as well as a decrease in alkaline phosphatase and acid phosphatase activities, in the liver and serum, indicating increased oxidative stress. Moreover, supplementation with 106 and 108 CFU/g E. acetylicum G1-33 enhanced the widespread expression of immune-related genes in the head kidney and liver, respectively, and improved resistance to Vibrio harveyi, whereas supplementation with 1010 CFU/g weakened this resistance. In conclusion, E. acetylicum G1-33, particularly at 108 CFU/g, emerged as an effective probiotic, optimizing growth performance and immunity in hybrid grouper. This research is pioneering in its application of E. acetylicum in mariculture, potentially broadening the range of probiotic strategies in aquaculture.

In vitro fish mucosal surfaces producing mucin as a model for studying host-pathogen interactions

Current prophylactic and disease control measures in aquaculture highlight the need of alternative strategies to prevent disease and reduce antibiotic use. Mucus covered mucosal surfaces are the first barriers pathogens encounter. Mucus, which is mainly composed of highly glycosylated mucins, has the potential to contribute to disease prevention if we can strengthen this barrier. Therefore, aim of this study was to develop and characterize fish in vitro mucosal surface models based on commercially available cell lines that are functionally relevant for studies on mucin regulation and host-pathogen interactions. The rainbow trout (Oncorhynchus mykiss) gill epithelial cell line RTgill-W1 and the embryonic cell line from Chinook salmon (Oncorhynchus tshawytscha) CHSE-214 were grown on polycarbonate membrane inserts and chemically treated to differentiate the cells into mucus producing cells. RTGill-W1 and CHSE-214 formed an adherent layer at two weeks post-confluence, which further responded to treatment with the γ-secretase inhibitor DAPT and prolonged culture by increasing the mucin production. Mucins were metabolically labelled with N-azidoacetylgalactosamine 6 h post addition to the in vitro membranes. The level of incorporated label was relatively similar between membranes based on RTgill-W1, while larger interindividual variation was observed among the CHSE in vitro membranes. Furthermore, O-glycomics of RTgill-W1 cell lysates identified three sialylated O-glycans, namely Galβ1-3(NeuAcα2-6)GalNAcol, NeuAcα-Galβ1-3GalNAcol and NeuAcα-Galβ1-3(NeuAcα2-6)GalNAcol, resembling the glycosylation present in rainbow trout gill mucin. These glycans were also present in CHSE-214. Additionally, we demonstrated binding of the fish pathogen A. salmonicida to RTgill-W1 and CHSE-214 cell lysates. Thus, these models have similarities to in vivo mucosal surfaces and can be used to investigate the effect of pathogens and modulatory components on mucin production.

Mix-match synthesis of nanosynbiotics from probiotics and prebiotics to counter gut dysbiosis via AI integrated formulation profiling

Antibiotics, improper food, and stress have created a dysbiotic state in the gut and almost 81% of the world's population has been affected due to the pandemic of COVID-19 and the prevalence of dengue virus in the past few years. The main intent of this study is to synthesize nanosynbiotics as nu traceuticals by combining probiotics, and prebiotics with nanoformulation. The effectiveness of the nanosynbiotics was evaluated using a variety of Nutra-pharmacogenetic assays leading to an AI-integrated formulation profiling was assessed by using machine learning methods. Consequently, Acetobacter oryzoeni as a probiotic and inulin as a prebiotic has been chosen and iron-mediated nanoformulation of symbiotic is achieved. Nanosynbiotics possessed 89.4, 96.7, 93.57, 83.53, 88.53% potential powers of Nutra-pharmacogenetic assays. Artificial intelligent solid dispersion formulation of nanosynbiotics has high dissolution, absorption, distribution, and synergism, in addition, they are non-tox, non-allergen and have a docking score of - 10.83 kcal/mol, implying the best interaction with Pregnane X receptor involved in dysbiosis. The potential of nanosynbiotics to revolutionize treatment strategies through precise targeting and modulation of the gut microbiome for improved health outcomes and disease management is promising. Their transformational influence is projected to be powered by integration with modern technology and customized formulas. Further in-vivo studies are required for the validation of nanosynbiotics as nutraceuticals.

Multi-Omics Reveals the Effects of Spirulina platensis Powder Replacement of Fish Meal on Intestinal Metabolism and Stress in Zig-Zag Eel (Mastacembelus armatus)

The booming aquaculture industry has created a strong demand for fishmeal and increased environmental pressures. Spirulina, as a potential alternative to fishmeal, has been shown to have growth-promoting and animal health-enhancing properties. In this study, 600 large spiny loaches, divided into five experimental groups, F0, F1, F2, F3, and F4, were reared for 10 weeks using Spirulina platensis powder (SPP) as a substitute for 0%, 5%, 10%, 15%, and 20% of fishmeal, respectively. The results of intestinal physiological indexes showed that superoxide dismutase was lower than F0 in all treatment groups, and the activity of F3 was significantly lower than F0 (p < 0.05). The activity of malondialdehyde was significantly higher than that of F0 in all groups except F3 (p < 0.05). The addition of SPP also led to a decrease in the activity of acid phosphatase in the intestine, which was significantly lower in all treatment groups compared to the F0 group (p < 0.05). The results of serum physiology showed that the activity of superoxide dismutase in serum gradually increased with the increase in the percentage of SPP addition, and the F3 group produced a significant difference from the F0 group (p < 0.05). The transcriptomics results showed that DEGs in the low percentage substitution group (<15%) were mostly enriched in metabolism-related pathways, such as bile secretion; DEGs in the high percentage substitution group (>15%) were mostly enriched in inflammation-related pathways, such as complement p and coagulation cascades. Metabolomics confirmed that nicotinate and nicotinamide metabolism and glycerophospholipid metabolism were the two pathways that were significantly enriched in the treatment groups of fishmeal replacement by SPP. The present study demonstrated that a low percentage (<15%) of fishmeal replacement by SPP in feed mobilized MA digestive metabolism, whereas a high percentage (>15%) of replacement induced intestinal stress. Considering the health and farm efficiency aspects, the proportion of SPP in feed formulation for MA should be less than 15%.

Probiotic Bacillus amyloliquefaciens B-1895 Improved Growth of Juvenile Trout

The aim of this study was to evaluate a new Bacillus amyloliquefaciens B-1895 probiotic as a feed additive for farmed trout. Final weight, absolute and average daily gain of fish, and average daily growth rate were higher in the group that received the probiotic than in the control group (p<0.05). Moreover, the probiotic-fed trout had more intense growth rates than the control group (higher by 15.7%; p<0.05). A decrease in feed ratio was also observed in the group that received probiotic (25% decrease; p<0.05), indicating more efficient digestion and assimilation of feed. In general, the introduction of probiotic in the feed did not adversely affect the functional status of the fish. In young trout of the control group, when assessing the general chemical composition of the organism in the muscle tissue revealed significantly (p≤0.001) higher level of moisture content by 5.1% and lower by 11.0% dry matter content. In muscle, the protein content was higher by 1.33% (p≤0.001) and fat content by 2.1% (p≤0.001) in experimental fish. Generally, Lactobacilli, Enterococcus, Vibrio, Bacillus, and coliform bacteria were found in the intestinal samples of rainbow trout. Significant reliable difference (p≤0.05) between the samples of experimental and control groups was noted in the content of Bacillus bacteria. In the control group, 5.0±0.4×103 CFU/g was detected, while in the experimental group 8.4±0.8×104 CFU/g. Overall, the data indicate that probiotic bacteria B. amyloliquefaciens B-1895 has no adverse effect on selected microorganisms in the study fish.

Effects of 2,4-dichlorophenol on non-specific immunity, histopathological lesions, and redox balance in African Catfish, clarias gariepinus (Burchell, 1822)

The toxic effects of 2, 4-dichlorophenol (2, 4-DCP) on aquatic organisms are well-established; however, the details regarding the mechanisms underlying the toxicity, especially immunotoxicity are poorly understood. Consequently, the aim of this study was to investigate the histopathologic, oxidative stress and immunotoxic effects attributed to exposure to sublethal concentrations of 2,4-DCP in the African catfish, Clarias gariepinus. Juvenile C. gariepinus were exposed to 0.4, 0.8, or 1.6 mg/L 2, 4-DCP for 28 days after which blood and head kidney were extracted for the determination of various nonspecific innate immune parameters while the liver was excised for histopathology examination and measurement of oxidative stress biomarkers. Control fish were maintained in water spiked 10 µL/L ethanol, representing the solvent control. A significant increase was noted in the activities of lactate dehydrogenase and superoxide dismutase as well as in levels of lipid peroxidation and DNA fragmentation in a dose-dependent manner, with higher adverse effects observed at the highest concentration tested (1.6 mg/L). The total white blood cells (WBC) count was significantly elevated in fish exposed to 2,4-DCP compared to control. Myeloperoxidase content was decreased significantly in fish exposed to 2,4-DCP especially at the highest concentration (1.6 mg/L) compared to controls. The respiratory burst activity did not differ markedly amongst groups. Histopathological lesions noted included edema, leucocyte infiltration, and depletion of hemopoietic tissue in the head kidney of exposed fish. There was significant upregulation in the mRNA expression of tumor necrosis factor (TNF-α) and heat shock protein 70 (HSP 70) but downregulation of major histocompatibility complex 2 (MHC 2) in exposed fish. Data demonstrated that exposure to 2,4-DCP resulted in histopathological lesions, oxidative stress, and compromised immune system in C. gariepinus.

The interaction between gut microbiome and bone health

PURPOSE OF REVIEW

This review critically examines interconnected health domains like gut microbiome, bone health, interleukins, chronic periodontitis, and coronavirus disease 2019 (COVID-19), offering insights into fundamental mechanisms and clinical implications, contributing significantly to healthcare and biomedical research.

RECENT FINDINGS

This review explores the relationship between gut microbiome and bone health, a growing area of study. It provides insights into skeletal integrity and potential therapeutic avenues. The review also examines interleukins, chronic periodontitis, and COVID-19, highlighting the complexity of viral susceptibility and immune responses. It highlights the importance of understanding genetic predispositions and immune dynamics in the context of disease outcomes. The review emphasizes experimental evidence and therapeutic strategies, aligning with evidence-based medicine and personalized interventions. This approach offers actionable insights for healthcare practitioners and researchers, paving the way for targeted therapeutic approaches and improved patient outcomes.

SUMMARY

The implications of these findings for clinical practice and research underscore the importance of a multidisciplinary approach to healthcare that considers the complex interactions between genetics, immune responses, oral health, and systemic diseases. By leveraging advances in biomedical research, clinicians can optimize patient care and improve health outcomes across diverse patient populations.

Interactions between the gut bacterial community of Exopalaemon carinicauda and infection by Enterocytozoon hepatopenaei

To explore the relationship between the intestinal flora of Exopalaemon Carinicauda and infection by Enterocytozoo Hepatopenaei (EHP), we analyzed the species and richness of gut microbiota in infected individuals in different EHP load groups [i.e., control (C), high load (H), and low load (L)] using gene sequencing after infection. The results showed that the abundance of intestinal flora in the high-load EHP group was significantly lower than that in the healthy group. Based on the UPGMA cluster tree and PCoA analysis, with comparisons to healthy shrimp, the gut microbiota of the EHP high load and low load groups were clustered into one branch, which indicated that EHP infection changed the composition of the gut microbiota of infected shrimps. The heat map analysis of species abundance clustering revealed that the dominant bacteria in the low EHP load group and the control group were beneficial genera such as Lactococcus, Ligilactobacillius, and Bifidobacterium, but the dominant bacteria in the high EHP load group were harmful genera such as Pseudomonas, Photobacterium, and Candidatus hepatincola. The functions of the intestinal flora predicted that most genes related to metabolism were more abundant in healthy shrimp, most genes related to metabolism and the organisms' system were more abundant in the low EHP load group, and most genes related to diseases and environmental information processing were more abundant in the high EHP load group. After separation and purification, the dominant bacteria (Bifidobacterium animalis in healthy shrimp and Lactococcus garvieae in the low EHP load group) and the non-dominant bacteria (Macrococus caseolyticus in the low EHP load group) were obtained. Each of these isolated strains were used together with EHP to infect E. carinicauda, and the results showed that Bifidobacterium animali and Lactococcus garvieae significantly reduced the EHP load in EHP-infected individuals. At the same time, the morphology and structure of the hepatopancreas and intestinal tissue of EHP-infected E. carinicauda were improved. No improvement was seen in tissue that was infected with Macrococus caseolyticus.

A Pretty Kettle of Fish: A Review on the Current Challenges in Mediterranean Teleost Reproduction

The Mediterranean region is facing several environmental changes and pollution issues. Teleosts are particularly sensitive to these challenges due to their intricate reproductive biology and reliance on specific environmental cues for successful reproduction. Wild populations struggle with the triad of climate change, environmental contamination, and overfishing, which can deeply affect reproductive success and population dynamics. In farmed species, abiotic factors affecting reproduction are easier to control, whereas finding alternatives to conventional diets for farmed teleosts is crucial for enhancing broodstock health, reproductive success, and the sustainability of the aquaculture sector. Addressing these challenges involves ongoing research into formulating specialized diets, optimizing feeding strategies, and developing alternative and sustainable feed ingredients. To achieve a deeper comprehension of these challenges, studies employing model species have emerged as pivotal tools. These models offer advantages in understanding reproductive mechanisms due to their well-defined physiology, genetic tractability, and ease of manipulation. Yet, while providing invaluable insights, their applicability to diverse species remains constrained by inherent variations across taxa and oversimplification of complex environmental interactions, thus limiting the extrapolation of the scientific findings. Bridging these gaps necessitates multidisciplinary approaches, emphasizing conservation efforts for wild species and tailored nutritional strategies for aquaculture, thereby fostering sustainable teleost reproduction in the Mediterranean.

From growth promotion to intestinal inflammation alleviation: Unraveling the potential role of Lactobacillus rhamnosus GCC-3 in juvenile grass carp (Ctenopharyngodon idella)

Lactobacillus rhamnosus is a probiotic, which not only promotes the growth of animals, but also has anti-inflammatory effects. However, the mechanism by which Lactobacillus rhamnosus regulates intestinal immunity is not well comprehended. Hence, the study aimed to research how Lactobacillus rhamnosus affects the intestinal immunity using juvenile grass carp (Ctenopharyngodon idella) as a model. We selected 1800 juvenile grass carp for testing. They were divided into six treatments and fed with six gradients of Lactobacillus rhamnosus GCC-3 (0.0, 0.5, 1.0, 1.5, 2.0, 2.5 g/kg) for 70 days. Enteritis was subsequently induced with dextroside sodium sulfate. Results indicated that dietary Lactobacillus rhamnosus GCC-3 addition improved growth performance. Meanwhile, appropriate levels of Lactobacillus rhamnosus GCC-3 alleviated excessive inflammatory response by down-regulating the expression of TLR4 and NOD receptors, up-regulating the expression of TOR, and then down-regulating the expression of NF-κB. Additionally, appropriate Lactobacillus rhamnosus GCC-3 improved intestinal immunity by reducing pyroptosis triggered by NLRP3 inflammasome and mediated by GSDME. Furthermore, 16 S rRNA sequencing showing appropriate levels of Lactobacillus rhamnosus GCC-3 increased Lactobacillus and Bifidobacterium abundance and decreased Aeromonas abundance. These results suggest that Lactobacillus rhamnosus GCC-3 can alleviate intestinal inflammation through down-regulating NF-κB and up-regulating TOR signaling pathways, as well as by inhibiting pyroptosis.

The effects of Bacillus subtilis on the immunity, mucosal tissue morphology, immune-related gene transcriptions, and intestinal microbiota in flounder (Paralichthys olivaceus) with two feeding methods: Continuous versus discontinuous feeding

Probiotics as dietary additives can improve weight gain, feed efficiency, and disease resistance in cultured fish. In this research, we evaluated and compared the effects of Bacillus subtilis on immunity, mucosal tissue morphology, immune-related gene transcriptions, and intestinal microbiota in flounder (Paralichthys olivaceus) by a 30-day feeding experiment based on a continuous feeding schedule (E1) and a discontinuous feeding schedule (E2). As a result, the use of B. subtilis exerted the best positive effects on survival rate, enzyme activity, mucosal tissue morphology, immune-related gene transcriptions, and intestinal microbiota in flounders. Alkaline phosphatase (AKP), lysozyme (LZM), and superoxide dismutase (SOD) activities in the liver of E2 were higher than those of E1 (P < 0.05). Furthermore, the villi length in the intestinal tract and the fold length in the stomach of E2 were also higher than in E1 (P < 0.05). The il-1 expression levels in the spleen were significantly increased in E2 (P < 0.05) compared to E1. We performed 16 S rRNA sequencing analysis to find that Bacillus in E1 (1.06%) and E2 (1.01%) had higher relative abundances than in E0 (0.053%) at the end of the experiments, indicating that short-term application of B. subtilis with the continuous or discontinuous feeding method can allow both the adaptation of the ecosystem to the presence of probiotics by the establishment of new species in the gut microbiota and the ability these new probiotic species to perform corresponding functions. No significant differences in the ability of probiotic establishment were observed between E1 and E2. Our findings provided a unique perspective to explore the mechanism of immune enhancement with probiotics and to screen the optimal administration strategy in aquaculture application for probiotic use. Together, these results point to some level of enhancement in immune status by continuous and discontinuous feeding after a short-term feeding period, which could be used as a prophylactic strategy for flounder health management.

Unlocking the growth potential: harnessing the power of synbiotics to enhance cultivation of Pleurotus spp

The oyster mushroom (Pleurotus spp.) is one of the most widely cultivated mushroom species globally. The present study investigated the effect of synbiotics on the growth and quality of Pleurotus ostreatus and Pleurotus pulmonarius. Different synbiotics formulations were applied by spraying mushroom samples daily and measuring their growth parameters, yield, biological efficiency, proximate composition, mineral content, total phenolic content (TPC), and diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging activity. Results demonstrated that the most significant yield of oyster mushrooms was harvested from synbiotics sprayed with inulin and Lactobacillus casei (56.92 g). Likewise, the highest biological efficiency obtained with a similar synbiotic was 12.65%. Combining inulin and L. casei was the most effective method of improving the mushrooms' growth performance and nutrient content in both samples. Furthermore, synbiotics that combined inulin and L. casei resulted in the highest TPC (20.550 mg gallic acid equivalent (GAE)/g dry extract (DE)) in white oyster mushrooms (P. ostreatus). In comparison, in grey mushroom (P. pulmonarius) the highest TPC was yielded by L. casei (1.098 mg GAE/g DE) followed by inulin and L. casei (1.079 mg GAE/g DE). The DPPH results indicated that the oyster mushroom could be an efficient antioxidant. The results revealed that applying synbiotics improved the mushrooms' quality by increasing their antioxidant capacity with higher amounts of phenolic compounds and offering better health benefits with the increased levels of mineral elements. Together, these studies demonstrated the potential of using synbiotics as a biofertilizer, which is helpful for mushroom cultivation; therefore, it might solve the challenge of inconsistent quality mushroom growers face.

Hematological changes in Florida pompano (Trachinotus carolinus) supplemented with β-glucan and Pediococcus acidilactici synbiotic

Florida pompano (Trachinotus carolinus) are a species of growing interest for commercial aquaculture. Effective health monitoring is crucial to the successful growout of the species, and prophylactic and therapeutic use of chemicals and antibiotics has been the traditional strategy for promoting stock health. However, concerns about antimicrobial resistance, chemical residues in seafood products and the environment, and resultant immunosuppression have prompted the industry to identify alternative management strategies, including supplementation with prebiotics, probiotics, and combinations of both (synbiotics). The objectives of this study are to determine and compare hematological, plasma biochemical, and plasma protein electrophoresis data of synbiotic-supplemented (β-glucan and Pediococcus acidilactici) and non-supplemented Florida pompano. Reference intervals for blood analytes are provided for both groups and for subgroups (females, males, large, and small fish) where statistically significant results exist. There are no differences between the hematological and plasma biochemistry analytes between the supplemented and control groups, except for blood urea nitrogen and carbon dioxide, indicating a possible effect of synbiotic supplementation on gill function and osmoregulation. Sex-related and size-related differences are observed within each of the control and supplemented groups; however, biometric measurements do not strongly correlate with blood analytes. These data represent baseline hematological and plasma biochemical data in the Florida pompano and indicate the safety of synbiotic supplementation in this commercially important species. This study serves to further the commercialization of Florida pompano by providing blood analyte reference intervals for health monitoring in the aquaculture setting.

A comprehensive review on the utilization of probiotics in aquaculture towards sustainable shrimp farming

Probiotics in shrimp aquaculture have gained considerable attention as a potential solution to enhance production efficiency, disease management, and overall sustainability. Probiotics, beneficial microorganisms, have shown promising effects when administered to shrimp as dietary supplements or water additives. Their inclusion has been linked to improved gut health, nutrient absorption, and disease resistance in shrimp. Probiotics also play a crucial role in maintaining a balanced microbial community within the shrimp pond environment, enhancing water quality and reducing pathogen prevalence. This article briefly summarizes the many ways that probiotics are used in shrimp farming and the advantages that come with them. Despite the promising results, challenges such as strain selection, dosage optimization, and environmental conditions are carefully addressed for successful probiotic integration in shrimp aquaculture. The potential of probiotics as a sustainable and ecologically friendly method of promoting shrimp development and health while advancing environmentally friendly shrimp farming techniques is highlighted in this analysis. Further research is required to fully exploit probiotics' benefits and develop practical guidelines for their effective implementation in shrimp aquaculture.

Dietary effect of multi-strain prebiotics and probiotics on growth, hemato-biochemical parameters, intestinal histomorphometry, and resistance to hypoxia in juvenile tambaqui (Colossoma macropomum)

This study evaluated the effects of a multi-strain prebiotics and probiotics on the diet of tambaqui Colossoma macropomum. One hundred and fifty juvenile tambaqui (20.2  ± 3.6 g and 10.32  ±  5.78 cm) were randomly distributed in 15 experimental units with a volume of 80 L and fed for 45 days with a diet containing the symbiotic additive at five inclusion levels (0, 2, 4, 6 and 8 g kg feed- 1). At the end of the period, growth performance, survival, hemato-biochemical and intestinal parameters, as well as the fish's resistance to stress were evaluated. The additive did not alter the growth performance, hemato-biochemical and intestinal parameters of the tambaqui. However, the hemato-biochemical parameters of aspartate aminotransferase (AST), plasma protein, hematocrit, glucose, triglycerides and cholesterol showed differences between treatments after the stress challenge. AST increased significantly during challenge and post-challenge. Plasma protein increased significantly during and after the challenge. The hematocrit was highest at 48 h after the challenge and lowest in the 2 g, 6 g and 8 g groups. Glucose was significantly reduced 24 h after the challenge, while triglycerides were lower 24 h and 48 h after the challenge. Cholesterol increased significantly in the challenge. There was an interaction between the factors sampling time and symbiotic concentration for hematocrit and glucose. In hypoxic stress situations, the 2 g concentration was more favorable for the fish. We recommend further studies with 2 g kg feed- 1 in trials lasting more than 45 days.

Strain-Specific Benefits of Bacillus Probiotics in Hybrid Grouper: Growth Enhancement, Metabolic Health, Immune Modulation, and Vibrio harveyi Resistance

In the realm of modern aquaculture, the utilization of probiotics has gained prominence, primarily due to their ability to enhance growth, boost immunity, and prevent diseases in aquatic species. This study primarily investigates the efficacy of Bacillus subtilis strains, both host-derived and from other sources, in influencing fish growth, immunity, lipid metabolism, and disease resistance. Employing a 42-day feeding trial, we divided hybrid grouper into four distinct groups: a control group on a basal diet and three experimental groups supplemented with 1 × 108 CFU/g of different Bacillus subtilis strains-BS, 6-3-1, and HAINUP40. Remarkably, the study demonstrated that the 6-3-1 and HAINUP40 groups exhibited significant enhancements across key growth parameters: final body weight (FBW), weight gain rate (WGR), feed intake (FI), feed efficiency ratio (FER), and feed conversion ratio (FCR). The investigation into lipid metabolism revealed that the 6-3-1 strain upregulated seven metabolism-related genes, HAINUP40 affected four metabolism-related genes, and the BS strain influenced two metabolism-related genes, indicating diverse metabolic impacts by different strains. Further, a notable reduction in liver enzymes AST and ALT was observed across all supplemented groups, implying improved liver health. Noteworthy was the BS strain's superior antioxidative capabilities, positively affecting all four measured parameters (CAT, GSH-Px, MDA). In the sphere of immune-related gene expression, the BS strain significantly decreased the expression of both inflammation and apoptosis-related genes, whereas the HAINUP40 strain demonstrated an upregulation in these genes. The challenge test results were particularly telling, showcasing improved survival rates against Vibrio harveyi infection in the BS and 6-3-1 groups, unlike the HAINUP40 group. These outcomes highlight the strain-specific nature of probiotics and their varying mechanisms of action within the host. In conclusion, this study reveals that probiotic strains, varying by source, demonstrate unique, strain-specific effects in promoting growth and modulating immunity in hybrid grouper. This research highlights the promise of tailored probiotic applications in improving aquaculture practices. Such advancements contribute to more sustainable and efficient fish farming methods.

Evaluation of different probiotics on growth, body composition, antioxidant capacity, and histoarchitecture of Mugil capito

We investigated the dietary effects of the single application of Saccharomyces cerevisiae, Lactobacillus bulgaricus, and their combination on growth, proximate composition of whole fish body, antioxidant defense, and histoarchitecture of hapa-reared Mugil capito. Healthy fish (Fish weighed = 10.30 ± 0.10 g at first) were randomly allocated into 4 equal groups, each with three replicates. These groups were designed as follows: (1) a group fed a basal diet without probiotics (control), (2) a group fed a diet containing S. cerevisiae (4 g/kg diet), (3) a group fed a diet containing L. bulgaricus (2 g/kg diet), and (4) the last group fed a diet containing a combination of both, all for a duration of 60 days. Probiotic-treated groups showed significantly better growth and nutrition utilization than the control group. Significant differences were observed in the crude fat and crude protein contents among the groups, with the combination group exhibiting the highest levels. However, there were no significant variations in ash content across all groups. The highest hepatic antioxidant capacity (superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) enzyme activities) was observed in the combination group. Thiobarbituric acid reactive substance (TBARS) concentrations were decreased significantly in all probiotic groups, suggesting improved oxidative stress resilience in these groups. The histomorphological analysis of the hepatopancreatic tissues revealed well-arranged parenchyma, increased glycogen storage, and melanomacrophage centers in probiotic-treated groups, particularly the combined probiotics group. Furthermore, the probiotic supplementation improved the histoarchitecture of the intestinal villi compared to the control group. To put it briefly, combined dietary administration of these probiotics improved growth, body composition, antioxidant defenses, and hepatic and intestinal health in hapa-reared M. capito, highlighting their promising role in promoting welfare and productivity.

Lippia sidoides essential oil at concentration of 0.25% provided improvements in microbiota and intestine integrity of Danio rerio

The study evaluated the effects of dietary supplementation with Lippia sidoides essential oil on the microbiota and intestinal morphology of Danio rerio. For this, 448 fish were randomly distributed in 28 tanks divided into a control group fed a commercial diet without supplementation, a group fed a commercial diet containing grain alcohol and five groups fed a commercial diet containing essential oil of L. sidoides (LSEO) at concentrations of 0.25%, 0.50%, 0.75%, 1.00% and 1.25%. After the period of dietary supplementation, biological materials were collected for microbiological and histological analyses. There were no significant differences regarding the microbiological count between the groups. Diversity of the microbiome was higher in 0.25% group than in control group. LSEO inhibited the growth of potentially pathogenic bacteria. Fish fed LSEO0.25% showed greater intestinal histomorphometric indices. The inclusion of LSEO at 0.25% in the diet of D. rerio provided improvements in fish microbiota and intestine integrity.

Exploring the effects of dietary inulin in rainbow trout fed a high-starch, 100% plant-based diet

BACKGROUND

High dietary carbohydrates can spare protein in rainbow trout (Oncorhynchus mykiss) but may affect growth and health. Inulin, a prebiotic, could have nutritional and metabolic effects, along with anti-inflammatory properties in teleosts, improving growth and welfare. We tested this hypothesis in rainbow trout by feeding them a 100% plant-based diet, which is a viable alternative to fishmeal and fish oil in aquaculture feeds. In a two-factor design, we examined the impact of inulin (2%) as well as the variation in the carbohydrates (CHO)/plant protein ratio on rainbow trout. We assessed the influence of these factors on zootechnical parameters, plasma metabolites, gut microbiota, production of short-chain fatty acids and lactic acid, as well as the expression of free-fatty acid receptor genes in the mid-intestine, intermediary liver metabolism, and immune markers in a 12-week feeding trial.

RESULTS

The use of 2% inulin did not significantly change the fish intestinal microbiota, but interestingly, the high CHO/protein ratio group showed a change in intestinal microbiota and in particular the beta diversity, with 21 bacterial genera affected, including Ralstonia, Bacillus, and 11 lactic-acid producing bacteria. There were higher levels of butyric, and valeric acid in groups fed with high CHO/protein diet but not with inulin. The high CHO/protein group showed a decrease in the expression of pro-inflammatory cytokines (il1b, il8, and tnfa) in liver and a lower expression of the genes coding for tight-junction proteins in mid-intestine (tjp1a and tjp3). However, the 2% inulin did not modify the expression of plasma immune markers. Finally, inulin induced a negative effect on rainbow trout growth performance irrespective of the dietary carbohydrates.

CONCLUSIONS

With a 100% plant-based diet, inclusion of high levels of carbohydrates could be a promising way for fish nutrition in aquaculture through a protein sparing effect whereas the supplementation of 2% inulin does not appear to improve the use of CHO when combined with a 100% plant-based diet.