Search Results (34)

Elevated ammonia nitrogen restricts sustainable hybrid grouper aquaculture. Though certain prebiotics relieve ammonia stress in groupers, their regulatory mechanisms remain unclear. This work investigated the protective effects and molecular mechanisms of xylo-oligosaccharides (XOSs) against ammonia stress in hybrid groupers (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) via a 4-week feeding trial (control diet/XOS-supplemented diet) followed by a 96 h ammonia challenge. Dietary XOS significantly boosted fish growth, increasing weight gain and specific growth rate while lowering feed conversion ratio (p < 0.05). During ammonia exposure, XOS-fed fish exhibited markedly higher survival from 48 to 96 h, with a 40% survival gap between the two groups at 96 h. XOS elevated serum glutathione peroxidase and lysozyme activities, suppressed catalase, aspartate transaminase and alanine transaminase levels (p < 0.05), strengthening antioxidant capacity, non-specific immunity and hepatic health. Transcriptomics identified differentially expressed genes enriched in nitrogen metabolism, steroid biosynthesis and complement cascades, verified by qPCR. XOS mitigated ammonia-triggered intestinal injury and reshaped gut microbiota: XOS supplementation enriched beneficial genera (Bifidobacterium, Turicibacter) and suppressed pathogenic taxa (Clostridium_sensu_stricto_1, Photobacterium) under ammonia stress. Collectively, dietary XOS improves hybrid groupers growth and ammonia resistance by regulating antioxidant enzymes, immune-related genes, intestinal morphology and gut microflora. This study offers theoretical support for developing anti-ammonia feed additives for grouper farming. Full article

Visceral white spot disease caused by Pseudomonas plecoglossicida poses a severe threat to large yellow croaker (Larimichthys crocea) aquaculture. This study investigated the immunomodulatory effects and underlying mechanisms of Pseudostellaria heterophylla extract against P. plecoglossicida infection in L. crocea. Fish were fed a basal diet supplemented with 1% P. heterophylla extract for 30, 45, and 60 days, followed by intraperitoneal injection with 200 μL P. plecoglossicida (1 × 10⁴ CFU/mL). When the control group reached about 50% mortality, transcriptome sequencing of head kidney tissues was performed on the 45 and 60 days post-feeding of the treatment groups to analyze gene expression changes following bacterial infection. Survival rates of the treatment groups were 33.33%, 13.33%, and 20% higher than those of the control group at 30, 45, and 60 days post-feeding, respectively. Transcriptomic analysis revealed time-dependent transcriptional responses: in one group, 45 days post-feeding, 10 differentially expressed genes (DEGs) were identified (2 up-regulated and 8 down-regulated), whereas in another group, 60 days post-feeding, 893 DEGs were detected (417 up-regulated and 476 down-regulated). Functional enrichment analysis (GO, KEGG, and GSEA) demonstrated that DEGs were significantly enriched in immune-related pathways, including Toll-like receptor signaling, chemokine activity, Th1 and Th2 cell differentiation, hematopoietic cell lineage, and cytokine–cytokine receptor interaction. Key immune genes, including chemokines, Toll-like receptors, and T cell regulators, were significantly up-regulated. These findings indicate that P. heterophylla extract enhances both the specific and non-specific immune capabilities of L. crocea in a time-dependent manner, with prolonged supplementation eliciting more robust transcriptional activation of immune defense pathways. This study provides a scientific foundation for developing immunological prevention strategies against P. plecoglossicida infection in aquaculture. Full article

This study identified δ¹⁵N stable isotope ratios as a robust tracer for fishmeal inclusion in aquaculture feeds. δ¹⁵N and δ¹³C values from fish muscle samples derived from feeding trials with seven species (n = 3–5 fish per diet group) were evaluated (+/−0.1‰ for both δ¹⁵N and δ¹³C; ~1% relative to % N and % C) to verify whether the presence or absence of fishmeal (FM) in feeds could be detected. C and N isotopic data were also analyzed for feed in two of the trials. δ¹³C signatures did not differ consistently across diet groups for each species examined, with mean δ¹³C values for all species investigated being −20.2‰ ± 1.3. In contrast, a strong δ¹⁵N distinction was discerned between FM- and non-FM-fed fish for both muscle and feed samples, with FM-fed groups presenting higher values (p < 0.01) than non-FM-fed groups (range 0.8 to 9.5‰). Dietary ingredients other than FM (e.g., fish oil and algal oil) did not impact the δ¹⁵N isotopic fingerprint, although the addition of poultry byproduct meal to plant-based salmon diets caused an average 0.3‰ difference in δ¹⁵N values. The findings are not absolute as CN isotopes can be used to detect large but not small differences in feed components. Additional research on threshold levels, ingredient sourcing, and species differences is warranted to refine the method to enhance industry transparency and seafood consumer confidence. Full article

Massilia varians has potential as a probiotic to inhibit bacterial pathogens in aquaculture, but very limited information is available regarding its use in Chinese mitten crab Eriocheir sinensis for enhancing host immunity, antioxidant ability and intestinal microbiota homeostasis. In this study, a 40-day feeding trial was conducted to evaluate the protective effects of dietary supplementation with M. varians P2-4 on nonspecific immune response, antioxidant status, intestinal microbiota and resistance against Pseudomonas aeruginosa infection in E. sinensis. Results demonstrated that dietary supplementation with M. varians P2-4 at 6.0 × 10⁶ to 6.0 × 10⁸ CFU/g diet significantly boosted nonspecific immunity and improved antioxidant capability of E. sinensis, mainly as evidenced by markedly increased activities of plasma lysozyme, plasma superoxide dismutase, hepatopancreatic superoxide dismutase and catalase. Furthermore, crabs fed M. varians P2-4-supplemented diets exhibited markedly improvements in intestinal microbiota composition and diversity, and showed substantially enhanced survival following P. aeruginosa challenge, with 7-day relative percentage survival ranging from 76.9% to 100.0%. To the best of our knowledge, this is the first study to reveal that M. varians P2-4 supplementation functions as a new biocontrol strategy in E. sinensis by effectively improving the non-specific immunity, antioxidant status and intestinal microbiota to mitigate P. aeruginosa infection. Full article

The effects of dietary tributyrin (TB) supplementation in juvenile Litopenaeus vannamei fed a high-soybean-meal diet were evaluated in an 8-week growth trial. The basal diet contained 24% fishmeal, while the experimental diet was supplemented with TB at 2.24 g kg⁻¹. Tanks were randomly assigned each dietary treatment in triplicate, with each tank consisting of 50 shrimp with 1.66 ± 0.24 g as an initial weight. Shrimp fed with the control diet exhibited the lowest growth, whereas supplementation with TB improved growth performance. For ADCs (apparent digestibility coefficients), non-significant variances were detected in dry matter, crude lipid, and crude protein; however, ash was highly significant in the control (0.00) group. Moreover, gross energy was highly significant in the TB-supplemented group. Whole-body and dorsal muscle proximate composition showed no substantial differences (p > 0.05), except that ash was highly significant in the whole body for the control diet, while lipids were highly significant in dorsal muscles for the TB diet. The biochemical, antioxidant and immune parameters of the hepatopancreas and hemolymph showed non-significant changes in both groups, except total protein (TP) and triglycerides (TGs) were highly significant in the TB-supplemented group in both the hemolymph and hepatopancreas. Conversely, malondialdehyde (MDA) was highly significant in the control group in the hemolymph. Non-significant changes were detected among treatment groups for most of the textural properties of the shrimp; however, hardness was highly significant in the control group. The TB group showed a highly significantly larger intestinal villus height (p < 0.05). Compared with shrimp fed a control diet, those receiving the tributyrin-supplemented diet showed improved gut morphology and structure, as well as enhanced histological characteristics of the hepatopancreas. Overall, TB supplementation significantly enhanced the specific growth rate, weight gain rate, final body weight, and intestinal morphology. Although some indicators were not affected, these results indicate that TB has potential as a valuable dietary supplement in aquaculture. Full article

As aquaculture adopts more sustainable feed formulations, interest in functional feed additives has grown to help mitigate the health and performance challenges associated with low-marine-ingredient diets. This study evaluated the effects of dietary supplementation with a commercial blend of mono-, di-, and triglycerides of short- and medium-chain fatty acids (SCFAs and MCFAs; BalanGUT™ AQ P, BASF) on growth, health, and disease resistance to Vibrio anguillarum in juvenile gilthead sea bream (Sparus aurata) fed practical low fishmeal and fish oil diets. Over an 8-week trial, fish were fed diets containing 0.3%, 0.5%, or 1% of a glyceride blend of SCFAs and MCFAs (BalanGUT™ AQ P) or a Control diet without functional additive supplementation. Growth performance and feed utilization were not affected by the supplementation of SCFAs/MCFAs glycerides, although non-significant trends (p > 0.05) toward improved specific growth rate (up to 12%) and reduced feed conversion ratio (up to 17%) were observed in sea bream fed supplemented diets, particularly during the 4 initial weeks and at the highest inclusion level (1%). Moderate (0.5%) and high (1%) supplementation levels of SCFAs and MCFAs significantly improved survival following Vibrio anguillarum challenge, despite no significant changes being observed in general systemic innate immune markers, such as serum lysozyme or ACH50 activities. SCFAs/MCFAs supplementation, particularly at 0.3% or 0.5%, also modulated intestinal morphology, including thinner submucosa and smaller goblet cell area in the posterior intestine, suggestive of a more homeostatic mucosa and reduced basal inflammation when feeding a low-FM/FO-based diet. These results suggest that the protective effects of this SCFAs/MCFAs glyceride blend are mediated primarily through local rather than systemic immune modulation. Overall, this study supports the use of functional SCFAs and MCFAs glyceride blends as a functional strategy to promote resilience and health in fish fed sustainable, low-marine-ingredient diets. Full article

Monosex all-male culture of the giant freshwater prawn (Macrobrachium rosenbergii) maximizes aquaculture yield due to a male growth advantage, but direct hormonal treatment of grow-out populations poses significant food safety risks. This study evaluated the efficacy of dietary 17β-estradiol (E2) in inducing functional neo-females from a fully all-male postlarval population to support an indirect monosex seed production strategy. All-male postlarvae were fed diets supplemented with E2 at concentrations of 0, 50, 100, 150, and 200 mg/kg for 36 days, followed by a 150-day hormone-free post-treatment period to assess growth performance, feminization rates, and gonadal histology. E2 administration successfully induced feminization across all treatments, reaching a peak rate of 35.5% at 150 mg/kg, whereas the control group remained entirely male. During the 36-day treatment period, E2 supplementation transiently enhanced specific growth and survival rates but concurrently reduced feed conversion ratios. Notably, these physiological differences disappeared completely over the 150-day post-treatment phase. Histological assessments confirmed that E2-induced neo-females exhibited normal oogenesis, with gonadosomatic index (GSI) values and oocyte diameters similar to those of wild-caught females. This establishes a definitive, physiologically safe, and non-surgical protocol for producing the neo-female broodstock necessary to sustain high-yield commercial monosex populations. Full article

Diatoms are recognized as a valuable source of bioactive compounds that can stimulate the immune defense mechanisms of fish. This study aimed to assess the effects of Chaetoceros sp. in modulating the specific and non-specific immunity of red hybrid tilapia through in vitro functional assays, an in vivo feeding trial, and a bacterial challenge. The in vitro experiment (Phase One) examined the immune response of tilapia cells exposed to Chaetoceros sp. extract, while the in vivo experiment (Phase Two) evaluated the immune response following an 8-week dietary supplementation with Chaetoceros sp. powder. In Phase One, an 8 mg/mL concentration of Chaetoceros sp. extract demonstrated an overall enhancement in lysozyme activity and lymphocyte proliferation. In Phase Two, tilapia fed a diet containing 2% Chaetoceros sp. showed significantly improved lysozyme activity, while the 5% supplemented group exhibited a significant increase in lymphoproliferation activity (p < 0.05). Growth performance parameters were generally comparable among dietary groups, indicating that supplementation did not adversely affect growth. Notably, the 2% diet also enhanced fish survivability following a challenge with Streptococcus agalactiae. These findings highlight the immunomodulatory potential of the diatom Chaetoceros sp. as a functional feed additive for freshwater fish, particularly red hybrid tilapia, and suggest its positive impact on fish health management in aquaculture. Full article

The induction of triploidy, a strategy to mitigate unwanted pre-harvest sexual maturation and a genetic containment measure for escaped farmed Atlantic salmon (Salmo salar), may give rise to challenges because of the distinct environmental and dietary requirements of sterile triploid fish. Smoltification is a critical phase in the life cycle of Atlantic salmon, so knowledge about parr–smolt transformation in triploids is important for the salmon farming industry. This study covered an investigation of hepatic expression of growth hormone receptor (GHrec) and insulin-like growth factor-I (IGF-I) genes, both of which are intimately involved in the regulation of osmoregulation and growth. Additionally, hepatic presence and location of IGF-I mRNA were examined using RNAscope^®, an advanced in situ hybridization technique. Triplicate groups of juvenile diploid and triploid salmon were reared at low temperature (10 °C) and fed either a standard diet or one enriched with hydrolyzed fish proteins from the start of feeding onwards. Liver samples were collected from three fish per tank each month from October to December (2454–3044 degree-days post-start feeding), the period encompassing smoltification, and hepatic expression of IGF-I and GHrec genes was quantified by real-time PCR. The results indicated that neither ploidy nor diet significantly influenced IGF-I or GHrec gene expression, suggesting that, under our conditions, triploidy and diet did not adversely affect this molecular pathway linked to growth and osmoregulation. IGF-I gene expression exhibited significant temporal variation, correlating with the progression of smoltification, while GHrec gene expression showed a similar, albeit non-significant, trend. Triploids exhibited IGF-I and GHrec gene expression patterns comparable to diploids, and both the temporal changes and lack of difference between triploids and diploids were mirrored in the quantification of IGF-I mRNA within the liver cells. The potential applicability to a commercial aquaculture setting requires further investigation. Full article

This study evaluated the effects of dietary supplementation with three silicate minerals (bentonite, zeolite, and illite) on the growth performance, whole-body composition, hematological and immune parameters, and apparent digestibility of Pacific white shrimp (Litopenaeus vannamei). Four isonitrogenous (35% crude protein) and isoenergetic (17.0 MJ kg⁻¹) diets were formulated: a control (CON) and three experimental diets containing 5% bentonite (BE), zeolite (ZE), or illite (IL), in which an equivalent amount of starch was replaced. Juvenile shrimp specimens (initial weight: 0.02 g) were reared for nine weeks and assessed for growth performance, feed efficiency, survival, biochemical indices, immune responses, and apparent digestibility. Shrimp specimens fed the illite-supplemented diet exhibited significantly higher final body weight (5.95 ± 0.97 g), weight gain, specific growth rate, and protein efficiency ratio than the other groups (p < 0.05). The feed conversion ratios were significantly better in the IL (1.10 ± 0.03) and ZE (1.16 ± 0.02) groups than that in the BE (1.26 ± 0.05) and CON (1.32 ± 0.04) groups (p < 0.05). The whole-body crude protein content was significantly higher in the ZE and IL groups. Hemolymph glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvate transaminase (GPT) activities were significantly reduced in the ZE and IL groups, indicating improved hepatic health. Non-specific immune responses, including nitro blue tetrazolium (NBT), phenoloxidase (PO), glutathione peroxidase (GPx), and lysozyme activities, were most enhanced in shrimp fed the IL diet. Apparent crude protein digestibility peaked in the IL group (93.3 ± 0.70%) followed sequentially by the CON (87.3 ± 0.92%), BE (87.8 ± 0.88%), and ZE (89.1 ± 1.11%) groups (p < 0.05). These findings demonstrate that dietary supplementation with illite significantly improves the growth performance, feed efficiency, hepatic condition, innate immune response, and protein digestibility of L. vannamei. Illite appears to be a promising candidate for functional feed supplementation aimed at enhancing productivity and health in intensive shrimp aquaculture. Full article

This study evaluated how dietary supplementation with Haematococcus pluvialis powder (HPP), Arthrobacter bussei powder (ABP), and A. bussei probiotics affects growth, whole-body composition, non-specific immunity, antioxidant capacity, and nutrient digestibility in Pacific white shrimp (Litopenaeus vannamei). Juvenile shrimps were fed for 8 weeks with five diets: a control diet (CON), H. pluvialis powder (HPP, 1%), A. bussei powder (ABP, 1%), or A. bussei probiotics at 10⁵ (ABL) or 10⁸ (ABH) CFU g⁻¹ feed. Shrimp fed the ABP diet exhibited the highest final body weight, weight gain, and protein efficiency ratio, with a significantly improved feed conversion ratio than that of CON, ABL, and ABH groups. The HPP group exhibited significantly better growth than that of the control. Regarding immunity and antioxidant responses, lysozyme and phenoloxidase specific activities, as well as glutathione peroxidase and superoxide dismutase specific activities, were significantly enhanced in shrimp fed ABP and HPP diets, whereas malondialdehyde levels were significantly reduced compared with those in CON. Apparent crude protein digestibility was significantly higher in all supplemented diets than those in the CON group, with ABP showing the highest value. ABP and HPP supplementation improved growth, protein digestibility, and immune-antioxidant responses in L. vannamei, whereas probiotic forms showed limited effects. ABP is a superior functional feed additive than its probiotic form for enhancing productivity and health in shrimp aquaculture. Full article

This study evaluated the performance of a recirculating aquaculture system (RAS) integrated with macroalgae (Ulva ohnoi) cultivation and sea urchin (Paracentrotus lividus) feeding, in a multi-trophic aquaculture approach. This system aimed to enhance sustainability through water bioremediation by macroalgae and valorization of the algal biomass as echinoderms feed. Over a 180-day trial, biomass production of U. ohnoi remained stable, with daily growth rates ranging from 7.4 to 24.4%. Statistical analyses (PCA and GAM) indicated no significant linear or non-linear relationship between macroalgae growth and environmental parameters (temperature, radiation, photoperiod). A theoretical estimate of nutrient production showed fairly stable values that do not statistically explain biomass production variation, highlighting the species’ adaptability. Sea urchins fed with fresh U. ohnoi showed regular growth, supporting the nutritional suitability of this macroalgae. For fish (Sparus aurata), no significant differences in growth or feed conversion ratio were observed between systems with and without algae. Parasitological monitoring revealed lower parasite loads and egg deposition in tanks in recirculation with U. ohnoi during certain periods, suggesting a potential role of macroalgae in reducing monogenean propagation. These findings underscore the feasibility of integrating Ulva cultivation into RAS, contributing to circular aquaculture models with improved sustainability and resource efficiency. Full article

Gamma-aminobutyric acid (GABA), a major inhibitory neurotransmitter, is used as a feed additive in aquaculture. However, its effects on muscle quality and lipid metabolism in fish remain understudied. Therefore, three diets supplemented with 0%, 0.01%, and 0.10% GABA were fed to juvenile Acanthopagrus latus (initial weight: 9.96 g) for 9 weeks, followed by analyses of growth performance, muscle quality indices, and hepatic lipid profiles. Fish fed 0.01% GABA showed the highest weight gain rate (p < 0.05). Their muscles exhibited improved muscle texture, higher levels of essential/non-essential and flavor amino acids, and a higher proportion of long-chain polyunsaturated fatty acids (LC-PUFAs), including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), along with triglycerides and cardiolipin enriched in LC-PUFA chains (p < 0.05). Moreover, their livers demonstrated increased levels of triglycerides, phosphatidylethanolamine, and LC-PUFA, along with reduced levels of phosphatidylcholine, lysophosphatidylcholine, lysophosphatidylethanolamine, and phosphatidylserine (p < 0.05). These results suggest that 0.01% GABA supplementation improves growth performance, enhances flesh quality, and optimizes liver lipid profiles in A. latus. Full article

This study investigated the immunonutritional potential of high-molecular-weight (Mw~85 kDa), non-degraded chitosan (NCS) and gamma-radiation-degraded, low-molecular-weight chitosan (RCS) incorporated into aquafeeds for Nile tilapia (Oreochromis niloticus). RCS was produced by γ-irradiation (10 kGy) in the presence of 0.25% (w/v) H₂O₂, yielding low-viscosity, colloidally stable nanoparticles with Mw ranging from 10 to 13 kDa. Five diets were formulated: a control, NCS at 0.50%, and RCS at 0.025%, 0.050%, and 0.075%. No adverse effects on growth were observed, confirming safety. Immune gene expression (e.g., ifng1, nfκb, tnf), antioxidant markers (e.g., reduced MDA, increased GSH and GR), and nonspecific humoral responses (lysozyme, IgM, and bactericidal activity) were significantly enhanced in the NCS-0.50, RCS-0.050, and RCS-0.075 groups. Notably, these benefits were achieved with RCS at 10-fold lower concentrations than NCS. Following challenge with Edwardsiella tarda, fish fed RCS-0.050 and RCS-0.075 diets exhibited the highest survival rates and relative percent survival, highlighting robust activation of innate and adaptive immunity alongside redox defense. These results support the use of low-Mw RCS as a biologically potent, cost-effective alternative to traditional high-Mw chitosan in functional aquafeeds. RCS-0.050 and RCS-0.075 show strong potential as immunonutritional agents to enhance fish health and disease resistance in aquaculture. Full article

The shift toward plant-based feeds in aquaculture necessitates a search for probiotics to improve the digestibility of such feeds and fish growth. This study characterizes four Bacillus strains for their probiotic potential in carp (Cyprinus carpio). Strains isolated from river sediments underwent in vitro screening for proteolytic/amylolytic activity, antibiotic sensitivity, and biofilm formation. Whole-genome sequencing was performed and functional annotation identified probiotic-related genes. All strains were identified as Bacillus velezensis and harbored genes providing thermal, osmotic, and oxidative stress resistance, alongside enzymes and bioactive metabolite synthesis pathways. Two non-antagonistic strain pairs were solid-phase cultivated on soybeans and incorporated into carp feed (0.1% w/w) for a 76-day trial, and growth metrics and gene expression were analyzed in juvenile fish. Group 1 (strains MT14 + MT42) exhibited a 40.75% higher biomass increase than the control group while Group 2 (strains MT141 + MT142) exhibited a 56.62% higher biomass growth. No significant gene expression changes occurred in juveniles, though MT141 + MT142 transiently modulated fry expression profiles. Therefore, these Bacillus velezensis strains synergistically enhance growth in carp that are fed plant-rich diets, highlighting their viability as aquaculture probiotics. Full article