Fish Immunity Research Articles

Nourishing Aquatic Life: A Comprehensive Reviewing of Fish Feed Strategies and Disease Combat in Aquaculture

With an increasing focus on creating sustainable methods that satisfy the nutritional requirements of aquatic life while successfully containing disease outbreaks, aquaculture has emerged as a crucial element of global food security. Nourishing Aquatic Life: A Comprehensive Review of Fish Feed Strategies and Disease Combat in Aquaculture explores the delicate balance between disease management and feed optimization, two crucial factors influencing the ecological sustainability and productivity of aquaculture systems. Innovative substitutes, including plant-based proteins, insect meal, and microbial sources, are being assessed alongside conventional fish feed formulations, which rely on fishmeal and fish oil to lessen environmental stresses while preserving high nutritional value. This article also covers how probiotics, prebiotics, and immunostimulants can improve fish immunity and resilience against common diseases, lowering the need for antibiotics and the likelihood of resistance. Additionally, we look at the most recent developments in fish feed formulation using biofloc, genetic engineering, and nanotechnology, emphasizing their implications for better fish health and disease resistance. These innovative strategies offer a hopeful vision for the future of aquaculture, inspiring us to continue our efforts in this field.

The Impact of Acute Ammonia Nitrogen Stress on Serum Biochemical Indicators and Spleen Gene Expression in Juvenile Yellowfin Tuna (Thunnus albacares).

The presence of ammonia nitrogen in water has a significant impact on the serum and spleen of fish, potentially leading to changes in substances such as proteins in the serum while also causing damage to the immune function of the spleen. To investigate the effects of ammonia nitrogen (NH3-N) stress on juvenile yellowfin tuna (Thunnus albacares), this study established three NH3-N concentrations, 0, 5, and 10 mg/L, denoted as L0, L1, and L2, respectively. Serum and spleen samples were collected at 6, 24, and 36 h. The effects of different NH3-N concentrations and exposure times on the physiological status of juvenile fish were investigated by analyzing serum biochemical indices and splenic gene expression. The results indicate that in the L1 group, the serum high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), complement 3 (C3) and complement 4 (C4) levels, and acid phosphatase (ACP) activity showed a trend of initially increasing and then decreasing. In the L2 group, the serum low-density lipoprotein cholesterol (LDL-C), HDL-C, and C4 levels and ACP activity also displayed an initially rising and then declining trend, while TG, C3, and creatinine (CRE) levels and alkaline phosphatase (AKP) activity showed an upward trend. In the L1 group, glutathione peroxidase 1b (GPX1b), interleukin 10 (IL-10), interleukin 6 receptor (IL-6r), and tumor necrosis factor alpha (TNF-α) gene expression levels in the spleen exhibited a trend of first increasing and then decreasing. In the L2 group, IL-10, IL-6r, tumor necrosis factor beta (TNF-β), caspase 2 (casp2), and caspase 9 (casp9) gene expression levels in the spleen also showed an initial increase followed by a decrease. When NH3-N levels are below 5 mg/L, it is recommended to limit stress exposure to no more than 36 h for the juvenile fish. For concentrations ranging from 5 to 10 mg/L, stress should be strictly controlled to within 24 h. Exposure to high NH3-N levels may affect biochemical indicators such as serum lipid metabolism, immunity, and metabolism in juvenile fish, and may damage the expression of antioxidant, immune gene, and apoptosis factors in the spleen. This study aims to deepen our understanding of the effects of NH3-N on juvenile tuna, with the goal of establishing effective water quality monitoring and management strategies. This will ensure the quality of aquaculture water, reduce the harm caused by NH3-N to juvenile yellowfin tuna, and enhance aquaculture efficiency and product quality.

Comparative analysis of Seabuckthorn and its significant component in enhancing fish mucosal immunity

Seabuckthorn and its significant component, gallic acid, were found to alleviate foodborne enteritis in zebrafish, a model species. To investigate the protective effects on mucosal immunity in cultured fish, seabuckthorn or gallic acid was added to soybean meal feed in a study conducted on juvenile grass carp. After a 5-week feeding trial, histopathology, enteritis-related gene expression, transcriptomics, and 16S rRNA gene sequencing were performed on the hindgut and liver tissues. The results showed that dietary inclusion of seabuckthorn (9.5 g/kg) or gallic acid (1.2 g/kg) prevented enteritis, evidenced by an increase in intestinal villi length and a decrease in goblet cell numbers. The gallic acid group showed benefits in preserving villi length, while seabuckthorn was advantageous in controlling goblet cells. On the molecular level, downregulation of pro-inflammatory genes and upregulation of anti-inflammatory genes were observed. Specifically, seabuckthorn was more effective in controlling cytokine expression, while gallic acid better protected the epithelial barrier function. Omics analysis revealed an upregulated hepatic “PPAR signaling pathway” in the seabuckthorn group and downregulated intestinal “platelet activation” in the gallic acid group, suggesting reduced inflammation and improved immune homeostasis. Regarding intestinal microbiota, both groups showed reduced pathogenic Campilobacterota and Aeromonas, and increased Bacteroides and Cetobacteria, potentially enhancing mucosal immunity. For anti-inflammatory processes, hepatic “fatty acid degradation”, “tryptophan metabolism”, and “FoxO signaling pathway” were elevated only in the seabuckthorn group. Gallic acid was advantaged with more “mitophagy” and “autophagy”. Fish-fed seabuckthorn or gallic acid were challenged with Aeromonas hydrophila to assess impacts on other mucosal surfaces. In the gill, compared to the soybean meal group, significantly higher survival rates, reduced CD4 inflammatory signals, and increased filament space were observed. Comparing seabuckthorn with its active component, seabuckthorn performed better in lipid metabolism, resistance to A. hydrophila, anti-inflammation, and probiotic abundance, while gallic acid mainly showed benefits for mucosal barrier protection, such as increased gill filament space. In summary, seabuckthorn and gallic acid improved mucosal immunity in fish, particularly in the gut and gills, enhancing resistance to bacterial infection and foodborne inflammation. Thus, gallic acid and seabuckthorn may be optimal phytotherapy choices in aquaculture.

Variation in the gut microbiota during the early developmental stages of common carp (Cyprinus carpio L.) and its correlation with feed and pond water microflora

BackgroundFish gut microbiota undergo dynamic changes under the influence of many factors and play an important role in the nutrition, immunity and development in fish. Although common carp (Cyprinus carpio L.) is an economically important freshwater fish, there are few reports on its gut microbiota changes at different early developmental stages. In the present study, the gut microbiota of common carp during the early developmental stages and its correlation with the feed and pond water flora were studied using the Illumina MiSeq sequencing platform.ResultsThe results showed that the gut microbiota of common carp underwent continuous and mild changes over the development process, and the pond water environment might provide bacterial resources and have a certain influence on the changes in the gut microbiota of common carp. However, host selection pressure played a more important role in shaping the gut microbiota. Although the gut microbiota was affected by many factors, the presence of core microbiota indicated that some bacterial species adapt to the gut microenvironment of common carp and played a role in its growth process.ConclusionsThe dynamic changes of gut microbiota of carp in early development stage were related to the feed, water environment and host selection. The results of this study provide a theoretical basis for healthy farming and disease prevention of common carp.

Preparation and immunological study of Ichthyophthirius multifiliis β-tubulin DNA vaccine in grass carp (Ctenopharyngodon idella)

Grass carp, a common aquatic species in China, suffer significant annual losses due to infection by the parasitic ciliate Ichthyophthirius multifiliis (Ich), thus necessitating effective prevention and control measures. In the present study, the Ich β-tubulin gene was cloned and inserted into the eukaryotic expression vector pVAX1 plasmid to construct the Ich β-tubulin DNA vaccine (pVAX1-Bt). After two doses of the pVAX1-Bt vaccine, the relative percentage survival (RPS) reached 70.0 %, whereas the RPS after 2 doses of pVAX1 reached 10.0 %. The β-tubulin antibody, specific antibody IgM, and immune enzymes (MDA, SOD, CAT, ACP, AKP, and cortisol) were tested over13 weeks. The findings revealed a significant enhancement in the vaccinated fish compared to their unvaccinated counterparts, indicating that the vaccine can activate the humoral immune pathway and non-specific immunity in fish, thereby promoting the production of specific antibodies and memory B cells. Collectively, these results indicate that the Ich β-tubulin DNA vaccine has potential in treatment of Ich infection (ichthyophthiriasis).

Quantitative and Weight Indicators of African Catfish Eggs and Larvae Development under Exposure to the Low-Power Ultrasound

Introduction. The growth of the world population and changing climate conditions on the planet induce the search for the innovative methods and technologies capable to increase the productivity and efficiency of the agricultural sector, and in particular — industrial fish-farming. In recent years, ultrasound has become one of such methods, widely used in many industries due to its unique properties and capabilities. In fish-farming, the use of ultrasound can significantly improve the processes of fish breeding by increasing the growth rate, improving digestion and overall health of fish, however, the issue of biostimulation of eggs and larvae with low-power ultrasound remains unexplored. The aim of this work is to study the biostimulation of eggs and larvae of African (clarias) catfish with ultrasound in aquariums as an advanced method of improving the growth and survival of this biological object at the early stages of its development, as well as a potential method for preventing the infectious and invasive diseases.Materials and Methods. The object of this study is an African clarias catfish, also known as the marbled clarias catfish (Clarias gariepinus). During the experiment, carried out at the fish-farm the “Marbled Catfish” Fish Farm” LLC (Lipetsk) from March to September 2023, 4 groups were formed — three experimental and one control. The eggs and larvae of the African catfish were exposed to the low-power ultrasound, in the experimental groups the exposure lasted for 30 s, 60 s and 120 s, respectively; the control group didn’t undergo any ultrasonic treatment. Biostimulation was carried out with a low-power submersible source of ultrasonic waves (0.243 W/cm2) and was performed 6 times. Sorting was carried out on the 15-th day from the start of incubation. In total, four series of experiment were carried out.Results. The first, second and third groups in all series of the experiment, according to sorting results, contained the largesized larvae of the African catfish in a percentage ratio of 44 to 46%; the percentage of the large-sized larvae in the control group was 19%. In terms of average-size, sorting gave the following result: in 1–3 experimental groups — from 52 to 54% of the total number of larvae; in the control one — 72%. For small-sized larvae, the following values were obtained: in groups 1–3 — from 2 to 3%, in the control group — 9% of the total number of larvae in the groups and series, respectively.Discussion and Conclusion. The growth and development of African catfish eggs and larvae are greatly influenced by the hydrological parameters of water: temperature, oxygenation, illumination, pH, hardness, content of hydrocarbonates, phosphates, nitrates and other chemical elements. In addition, fertilization of eggs may occur unevenly due to non-uniform mixing of eggs and milt, quality and maturity of eggs during fertilization, which can result in different quantitates of the catfish larvae output. The exposure of eggs and larvae to the ultrasound in the experiment resulted in an increase of a number of large-sized larvae, which is favourable for obtaining the fish seed material. Timely sorting of fish seed material before transferring an African catfish to the closed water supply systems reduces the cannibalism during further cultivation. The use of ultrasound in fish-farming requires further study to identify the optimal frequency of treatment and the effect on the commercial fish immunity and growth rate, which will foster the satisfaction of the growing needs of the population in the high-quality products of fishing industry.

Tapeworm infection affects sleep-like behavior in three-spined sticklebacks

Sleep is a complex and conserved biological process that affects several body functions and behaviors. Evidence suggests that there is a reciprocal interaction between sleep and immunity. For instance, fragmented sleep can increase the probability of parasitic infections and reduce the ability to fight infections. Moreover, viral and bacterial infections alter the sleep patterns of infected individuals. However, the effects of macro-parasitic infections on sleep remain largely unknown, and measuring sleep in non-model organisms remains challenging. In this study, we investigated whether macro-parasite infections could alter sleep-like behavior of their hosts. We experimentally infected three-spined sticklebacks (Gasterosteus aculeatus), a freshwater fish, with the tapeworm Schistocephalus solidus and used a hidden Markov model to characterize sleep-like behavior in sticklebacks. One to four days after parasite exposure, infected fish showed no difference in sleep-like behavior compared with non-exposed fish, and fish that were exposed-but-not-infected only showed a slight reduction in sleep-like behavior during daytime. Twenty-nine to 32 days after exposure, infected fish showed more sleep-like behavior than control fish, while exposed-but-not-infected fish showed overall less sleep-like behavior. Using brain transcriptomics, we identified immune- and sleep-associated genes that potentially underlie the observed behavioral changes. These results provide insights into the complex association between macro-parasite infection, immunity, and sleep in fish and may thus contribute to a better understanding of reciprocal interactions between sleep and immunity.

Combined Dietary Spirulina platensis and Citrus limon Essential Oil Enhances the Growth, Immunity, Antioxidant Capacity and Intestinal Health of Nile Tilapia.

The dietary presence of feed additives is crucial for boosting fish growth and immunity. Accordingly, this feeding trial aimed to investigate the effects of the separate and concurrent dietary supplementation of Spirulina platensis (SP) and bitter lemon (Citrus limon) peel essential oil (LEO) on the growth, immunity, antioxidant capacity, and intestinal health of Nile tilapia (Oreochromis niloticus). Four groups of male Nile tilapia were employed. The first group (control) was given the basal diet, while the second and third groups received the basal diet supplemented with LEO extract (1%) and SP (1 g/kg diet), respectively. The fourth group received the basal diet supplemented with a mix of LEO (1%) and SP at 1 g/kg. After two months of feeding, using LEO or/and SP improved the overall growth and immunological parameters, with their combination yielding the best outcomes. The supplementation of LEO or/and SP improved the Nile tilapia's growth metrics and transcriptomic levels of growth-regulating genes such as (oligo-peptide transporter 1 (Pep1), growth hormone receptors 1 (GHR1), and insulin-like growth factor (IGF1). The improved growth performance was linked to significant increases in the expression levels of mucin and fat metabolism-related genes. Moreover, fish supplemented with LEO, SP, or their combination showed enhanced non-specific immunological measures, including phagocytic and lysozyme activities and the mRNA copies of its regulating genes. Additionally, remarkable increases in the antioxidant enzyme activities and the mRNA levels of their related genes were detected. The complement (C3) gene's transcriptomic level was also significantly increased. Furthermore, the dietary supplementation of LEO, SP, or their combination improved the histological structures of the spleen, hepatopancreas, and intestine. The enhanced effects of LEO, SP, or their combination on fish immunity and growth are suggested to be due to their contents of bioactive compounds with anti-inflammatory, antioxidant, and antimicrobial properties. Thus, using the LOE and SP blends as feed additives is recommended for better growth and immunity of Nile tilapia.

Investigation of the Effects of Heavy Metals (Copper, Cobalt, Manganese, Selenium, and Zinc) on Fish Immune Systems – An Overview

Abstract Aquaculture, as a strategic and developmental industry, plays an important role in ensuring food security and economic stability within countries. This crucial sector faces various influences, including infectious and nutritional diseases. Certain minerals function as essential nutrients, playing a main role in processes across all aquatic animals when present in appropriate dietary proportions. Studies showed that some heavy metals serve as a catalyst for various biological functions, including the maintenance of colloidal systems, acid-base balance, bone formation, and the regulation of fundamental natural elements such as vitamins, hormones, and minerals. Fish acquire essential elements crucial for their well-being through both diet and water sources. Adequate levels of essential elements, such as iron, zinc, copper, cobalt, manganese, and selenium, in the diet contribute to enhanced growth, increased survival rates, improved disease resistance, and heightened specific immunity in fish. When incorporated in appropriate quantities, these elements play a pivotal role in disease prevention, fostering the production of high-quality fish, minimizing economic losses, and solidifying aquaculture as a robust and profitable industry. This article aims to delve into the immunological effects induced by metal elements, specifically copper (Cu), cobalt (Co), manganese (Mn), zinc (Zn), and selenium (Se), in diverse fish species. The objective is to underscore the significance of this exploration, paving the way for the development of more potent immune supplements in the future. These supplements have the potential to improve growth, fortify immune responses, and enhance resilience against diseases in various fish species.

Supplementation with Akkermansia muciniphila improved intestinal barrier and immunity in zebrafish (Danio rerio)

Akkermansia muciniphila (Akk), a second-generation probiotic known for its ability to regulate intestinal function in mammals, is not yet fully understood in the context of aquaculture. This study aims to investigate the effects of different forms of Akk on intestinal barrier function and immune response in zebrafish (Danio rerio) under high-fat diet conditions. The experimental groups included a control group, a high-fat diet group, an Akk group, and a group receiving various concentrations of pasteurized Akkermansia muciniphila (P-Akk) along with a high-fat diet. Evaluation methods included histological examination with hematoxylin and eosin staining, ultrastructural analysis using transmission electron microscopy, real-time fluorescence quantitative analysis, and transcriptome sequencing technology. The results showed that both the Akk and P-Akk groups exhibited a significant increase in villi number and length compared to the high-fat group. Furthermore the expression levels of claudin, claudin-2, occludin A, occludin B, and other genes were significantly upregulated, while the expression levels of intestinal proinflammatory factors genes and proteins were significantly downregulated. Compared to the high-fat group, the Akk group showed a more complete and well-preserved nucleus, mitochondria, and tight junction structures. Additionally, the morphology of intestinal epithelial microvilli in the medium and high concentration Akk group was complete and dense. The expressions of tlr2 and nf-κb were upregulated, while the expressions of myd88 and nod2 were downregulated in the medium- and high-concentration Akk groups. Akk may improve immune dysfunction in high-fat fed zebrafish through the TLR2/NF-κB signaling pathway, which requires further study. Transcriptome analysis revealed significant upregulation of the immune-related gene pigr, significant downregulation of stat3, and significant upregulation of the intercellular adhesion molecule f11r. In conclusion, dietary Akk supplementation alleviated intestinal barrier damage and immune dysfunction in high-fat zebrafish. This study provides important insights into the potential use of Akk in fish and lays the foundation for further studies on its role in fish immunity.

EFFECT OF ADDING BIOACTIVE COMPOUNDS FROM BROWN ALGAE (Sargassum sp.) IN FEED ON INTESTINE AND LIVER HISTOLOGY OF SIAM PATIN FISH (Pangasius hypopthalmus) SEEDS

Addition of Sargassum sp. into feed as a feed supplement is one effort that can be done to increase fish growth and immunity. This research aims to determine the effect of adding bioactive compounds from Sargassum sp. extract in feed on the health picture of Siamese catfish through structural changes that occur in the intestines and liver. Fish observations were carried out for 40 days. The results obtained regarding the survival rate (SR) value of Siamese catfish seeds show that there is no difference or has the same percentage, namely 100%. The results of observations on the histopathology of intestinal organs analyzed in a comparative descriptive manner showed that Siamese catfish fry were fed with Sargassum sp. extract experienced damage than fish seeds fed without the addition of Sargassum sp. extract (control). The damage that occurs includes leukocyte infiltration (IfL), necrosis (Ne), goblet cell proliferation (Psg), hyperplasia (Hpl), and hemorrhage, with a damage score analyzed using the semiquantitative scoring method, namely 1. Damage to the liver, namely experiencing congestion in the blood vessels.

Connection between the gut microbiota of largemouth bass (Micropterus salmoides) and microbiota of the aquaponics system environment.

The significant role played by the gut microbiota in fish growth, development, immunity, and overall health has been widely established. Nevertheless, there remains a lack of clarity regarding the interaction and origin between the environmental microbiota and the gut microbiota of aquaculture species within the aquaponics coupling system. Thus, we conducted an analysis of the gut microbiota of largemouth bass (Micropterus salmoides) obtained from an indoor enclosed circulating water aquaponics coupling system located in greenhouses in northern China. Additionally, we examined the microbiota of the fish pond water and tomato rhizosphere soil using high-throughput sequencing of the 16S rRNA gene. Our results demonstrated significant differences in the compositions of fish pond water, rhizosphere soil, and the gut microbiota of largemouth bass. Moreover, these compositions changed throughout the culture period. Approximately 11.99% of the bacterial composition in the gut microbiota of largemouth bass could be attributable to the rhizosphere soil microbiota, while 62.01% of the bacterial composition could be attributable to the fish pond water microbiota. However, the proportion of bacteria in the gut microbiota from the fish pond water microbiota remained respectively 40.90% and 56.15% in May and September, which increased markedly to 88.97% in July. Similarly, the proportion of bacteria in the pond water microbiota from the tomato rhizosphere soil microbiota were respectively 0% and 8.95% in samples collected in May and September, which increased markedly to 69.26% in July, and the proportion of bacteria in the gut microbiota from the tomato rhizosphere soil microbiota were respectively 0.07% and 0% in samples collected in May and September, which increased to 0.45% in July. The research results offer essential insights into the interactions and origins of environmental microbiota and gut microbiota in the aquaponics system of cultured fish. This knowledge could enhance green aquaponics practices for largemouth bass.

Immunostimulant In Fish Hatchery- A Tool In Pharmacological Research

Fish is an aquatic animal that is used as food and presently they are used in scientific research. They provide a simple system for biomedical research and hence there is an increase in demand for fish production due to its dynamic purposes. The fish are less sentient and they have a high potency with the homology of mammals hence they are used as a model in pharmacological research. The various fish that are used are zebra fish, rainbow trout fish, medaka fish, etc. Various husbandry techniques were introduced to increase the production of fish. Their intensification led to poor-quality of fish production. Immunostimulants are drugs that enhance the innate immunity of fish and increase their resistance to the disease. They are biological and synthetic compounds that increase phagocytic, lysosomal, and bactericidal activity by directly activating the immune cells and NK cells and helping in the control of disease. They are used in the pharmacological research of toxicology, genetics, cancer research, biomedicine, neurobiology, endocrinology, ecology, and gerontology, and also in the development of biology and act as a model to provide elemental knowledge on biological science.

Sexual dimorphism in fish innate immunity: A functional and transcriptional study in yellowtail kingfish

Sexual dimorphism in immunity has been extensively documented across vertebrates, with marked contrasts observed in immune responses between males and females. These variations are mainly attributed to oestrogens conferring enhanced immune responses in females, while males exhibit greater susceptibility to pathogens. However, in the light of the data, consensus is lacking, as different physiological and environmental factors such, as epigenetics, may impact sex-biased immunity. In fish, the regulation of immune responses through sex hormones is primarily determined by the leucocyte function, which contains sex steroid receptors. However, comparative sex-based research in fish immunity is still very limited. This study aimed to evaluate, for the first time, the disparities between males and females yellowtail kingfish (Seriola lalandi) juveniles in several parameters of local humoral innate immunity related to mucosae (skin mucus and foregut homogenates) and reproductive tissue (ovary and testis homogenates), as well as in serum. We investigated the sexual dimorphism in the expression patterns of genes coding for antimicrobial peptides, antiviral markers, and cytokines. Our findings revealed that the yellowtail kingfish males exhibit significantly higher levels of innate immune parameters, both functionally and transcriptionally, compared to females. These results suggest that females may have a higher susceptibility to pathogen infections, potentially leading to latent infections, which deservers further investigations. Understanding these sex-based differences in immunity could guide breeding strategies improvements and disease management in aquaculture facilities.

A superior chitin product: Black soldier fly larvae chitin, beneficial to growth performance, muscle quality and health status of largemouth bass Micropterus salmoides, in comparison to shrimp chitin

We appraised the effects of black soldier fly larvae chitin (BSFC) with four levels (0.4 %, 0.8 %, 1.2 % and 1.6 %) and shrimp chitin (SC) with three levels (0.4 %, 0.8 % and 1.6 %) in diets on the growth performance, nutrient composition and health status of largemouth bass (8.00 ± 0.29 g) fed for 56 days. The results showed that the dietary 0.4 % BSFC distinctly increased the specific growth rate and weight gain rate of fish (P < 0.05), and evidently promoted the deposition of C22:1n-9, C24:1n-9 and increased total monounsaturated fatty acid content in the muscle (P < 0.05). BSFC and SC distinctly stimulated the secretion of β-N-acetylglucosaminidase in the hindgut (P < 0.05). The antioxidant status of fish was improved by BSFC and SC, which was attributed to the decreased malonaldehyde contents in the muscle and midgut and the increased total superoxide dismutase and catalase activities in the midgut. The 1.2 %–1.6 % BSFC and 0.8 %–1.6 % SC enhanced the non-specific immunity of fish, which was attributed to the marked promotion of lysozyme, acid phosphatase and alkaline phosphatase activities by BSFC and the distinct enhancement of lysozyme activity by SC in the serum or midgut (P < 0.05). BSFC and SC notably reduced the abundance of potential pathogenic bacterium Vibrio and Photobacterium (P < 0.05), and 0.4 %, 1.2 %, 1.6 % BSFC and 0.4 % SC markedly increased the abundance of probiotic bacterium Cetobacterium (P < 0.05), and the BSFC and SC of 0.8 % significantly increased the abundance of the probiotics Bifidobacterium and Bacillus respectively (P < 0.05). The increase of acetic acid, propionic acid, butyric acid and valeric acid concentrations in the hindgut might be related to the increase of intestinal probiotics, and 0.8 %–1.6 % BSFC and 0.4 % SC obviously increased the total short-chain fatty acid levels in the hindgut (P < 0.05). BSFC and SC remarkably reduced muscle fiber area and diameter (P < 0.05), while fiber densities were significantly increased under 0.4 %, 0.8 % BSFC and 0.4 % SC supplementation (P < 0.05), which was accordant with increased mRNA expression levels of myod, myf-5, smad-2, tgf-β1 and decreased mRNA expression levels of myos in the muscle. Collectively, BSFC and SC had no negative effect on the growth of largemouth bass, and improved the health status of fish. The dietary 0.4 % BSFC supplementation was beneficial to fish growth and muscle quality, and BSFC was a superior chitin product in comparison to SC.

The impact of plant cryoextract on productivity and factors of innate immunity of pond fish against the background of stress in the experiment

The search for effective and environmentally friendly means to increase the productivity and natural resistance of animals, especially in aquaculture, remains an urgent socio-economic task. This article presents the results of the study of the effect of the cryobiological supplement ‘Immunolife-Fish’, based on medicinal plants, on the weight gain of juvenile common carp (Cyprinus carpio) and indicators of innate immunity of two-year-old common carp (Cyprinus carpio) and silver carp (Hypophthalmichthys molitrix) under the influence of thermal stress factor in aquarium conditions. It was found that the weight gain of juvenile carp treated with the cryobiological supplement ‘Immunolife-Fish’ was higher than that of the control group at all stages of the study. The increase was most pronounced during the first 42 days of feeding. A significant increase in the number of leukocytes was found in the blood of fish (common carp and silver carp) exposed to a heat stressor compared to control values. In fish that received a supplement of the herbal preparation during stress, this indicator only tended to increase. The effect of the stressor in fish of both species is manifested by a significant increase in the leukocyte content, a decrease in the indicators characterizing the functional state of cellular immunity — phagocytic activity and number of phagocytes, as well as a tendency to decrease the phagocytic index of neutrophils in the blood. The use of the cryobiological supplement ‘Immunolife-Fish’ in fish exposed to stress not only prevented the decrease in the phagocytic activity of neutrophils but also contributed to a slight increase in their activity in comparison with the control. A significant decrease in the activity of lysozyme and the level of circulating immune complexes, as well as an increase in the content of seromucoids, was found in the blood serum of common and silver carp under the influence of the stress factor. The use of the drug against the background of stress leveled the negative changes in the above indicators characterizing the state of the humoral link of innate immunity. In addition, a mild immune stimulating effect of the cryobiological supplement on fish of both species, which were kept in optimal conditions, was noted. The research is aimed at the development and testing of organic, environmentally friendly anti-stress and immunostimulant agents in commercial fish farming

Impact of Chaetomorpha aerea-enriched diet on growth, feed utilization, and haemato-immunological responses in Clarias batrachus challenged with Aeromonas hydrophila

The bacteria Aeromonas hydrophila, which causes motile Aeromonas septicemia (MAS), is dangerous to aquaculture because it affects the fish's well-being and production. As the aquaculture industry seeks sustainable and effective methods to enhance fish immunity and growth, natural supplements such as marine algae have gained attention. This study explored the potential benefits of incorporating the green marine algae Chaetomorpha aerea into the fish diet, focusing on disease resistance, growth, feed utilization, and hematological and immunological responses. Five diets were prepared, varying concentrations of C. aerea (0 control, T1: 1 g/kg; T2: 2 g/kg: T3: 5 g/kg: and T4: 10 g/kg) and administered to fish over 30 days. Following the feeding trial, the fish were exposed to A. hydrophila, and their survival rates were observed for the next 14 days. The findings demonstrated that the final weight, weight gain, relative growth rate, specific growth rate, and daily growth rate were all positively impacted by a diet containing 5 g/kg of C. aerea. Additionally, fish in the 5 g/kg C. aerea group demonstrated improved feed conversion efficiency compared to the control group. While there were no significant changes in red and white blood cell counts on the initial day, serum lysozyme activity and overall resistance to infection were enhanced in fish receiving C. aerea at 2 and 5 g/kg. These results imply that C. aerea supplementation with fish supplements may be a useful immunostimulant, boosting improved health and growth in sustainable aquaculture practices.

Oral administration enhances directly mucosal immune system in intestine of olive flounder (Paralichthys olivaceus)

Aquaculture is notably vulnerable to diseases, with Edwardsiella tarda causing significant mortality across various commercially important fish species in both freshwater and marine environments. In the aquaculture industry, sustainable disease control hinges on the effective development of vaccines. Oral vaccines present an appealing approach to immunization in fish due to their ease of antigen administration, reduced stress compared to non-oral delivery methods, and their potential applicability to both small and large finfish species. In mammals, the exposure of mucosal surfaces to antigens results in the secretion of antigen-specific IgA at these locations. Mammals have a common mucosal immune system, in which stimulation of one epithelium can also give rise to specific IgA or IgM responses in other mucosal organs. Mucosal immunoglobulins are particularly important in developing vaccines that provide mucosal immunity. However, it remains unclear whether fish share a common mucosal system. Moreover, neither Peyer's patches nor intestinal lymph nodes were identified. Nevertheless, oral vaccination remains an attractive method for inducing immunity. We investigated whether the activation of the mucosal immune response was induced by direct injection of the antigen. After oral antigen administration, antigen-specific antibody titers increased in the experimental group (E. tarda FKC vaccine). In the challenge experiment, the cumulative survival rate was 72% (E. tarda). This suggests that oral administration of antigens can activate intestinal mucosal immunity in flounders. Additionally, these results help understand the intestinal mucosal immune system of teleost fish. In the future, research on the signaling mechanisms of these genes is expected to provide helpful information for developing vaccine adjuvants.

Supplementing Nile tilapia (Oreochromis niloticus) (Linnaeus, 1758) larvae with dietary beta-glucan could improve their growth, survival, immune function, intestinal and liver histomorphology

Abstract Β-glucan exerts a positive impact and consider as a functional feed additives to enhance fish growth, immunity, control disease outbreaks and pathogen infections by increasing functional, immune and decreasing harmful responses. The present study aimed to determine the most effective dietary level of beta-glucan (βG) to improve Nile tilapia Oreochromis niloticus (L.) fry growth performance, feed utilization, and hematological indicators. Seven isonitrogenous (32% crude protein) and isocaloric diets (18 MJ/kg) were formulated. All diets were identical except for the variation in βG levels.The basal experimental diet (control diet) had no βG added. Diets 2–7 each contained βG at levels of 250, 500, 1000, 2000, 4000, and 8000 mg/kg diet, respectively. A total of 840 fish with an average body weight of 0.2±0.01 g were allocated into the seven experimental treatments (in triplicate). The trial lasted for 120 days, Nile tilapia fry growth performance and feed utilization were significantly (P≤0.05) higher in all treatments receiving βG diets than in the control diet. The fish fed with ßG0.1 diet showed the highest significant growth induces and the best FCR values. The survival (S%) of the fish also showed a significant increase in the βG diets up to ßG0.8 levels, when compared to the other experimental diet groups. All hematological parameters increased (P≤0.05) in fish fed with a diet supplemented up to ßG0.8 compared to the control group. Histological examination of the intestine and liver in the control group revealed histopathological alterations in the villi. On the other hand, the groups treated with βG had longer and structurally normal villi. The most well-preserved intestinal tissue and the tallest villi were observed in ßG0.1, followed by ßG0.050 and ßG0.8 groups. In the liver, the control group exhibited fatty degeneration, necrosis and pyknosis whereas the ßG0.1 group displayed the most preserved hepatic tissue, followed by ßG0.8 and ßG0.2 groups. The results indicate that according to FBW-based broken-line model analysis, the optimal dietary level of βG for Nile tilapia fry to exhibit superior growth and diet utilization efficiency associated with the best FCR for Nile tilapia should be 0.12% βG /kg diet. To increase the immunity of fish and improve the properties of hematological and histopathological indices, the dose can be increased to 0.8% βG without any adverse effects.

Role of ginger in fish nutrition with special emphasis on growth, health, gut and liver morphology

AbstractGinger, Zingiber officinale, is a medicinal herb widely used for its distinct flavor and medicinal properties. It contains various bioactive compounds, including zingerone, shogaols, gingerol saponin, polyphenols, and flavonoids, which confer anti‐inflammatory, antioxidant, and immunomodulatory effects. Ginger and its derivatives such as powder, essential oil, and active ginger extracts have been used as natural functional ingredients with health‐promoting and disease‐preventing properties. In recent studies, ginger derivatives have been tested in aquafeeds for their potential as safe herbal medicines. They have shown several benefits, acting as growth promoters and modulators of physiological and biochemical functions. Ginger has been found to improve growth performance, modulate immunity, and enhance disease resistance in fish. Its organic constituents exhibit potent anti‐stress, antibacterial, antiviral, and antiparasitic activities, thereby boosting the specific and nonspecific immunity of aquaculture fish. This review provides a comphrensive summary of studies exploring the effects of dietary ginger on various aspects of fish health including growth performance, blood parameters, immunity, disease resistance, gut morphology, antioxidant status, and molecular mechanisms. Furthermore, the review emphasizes the necessity of elucidating the specific bioactive compounds in ginger responsible for its biological functions and their mechanisms of action against infectious diseases in different fish species.