Protective effect of chitin and chitosan enriched diets on immunity and disease resistance in Cirrhina mrigala against Aphanomyces invadans

Black soldier fly larvae meal as a potential modulator of immune, inflammatory, and antioxidant status in gilthead seabream juveniles

This study aimed to evaluate the effects of fish meal (FM) replacement with defatted Hermetia illucens larvae meal (HM) on the hematological profile, immune parameters, intestinal inflammatory status, and antioxidant response in gilthead seabream juveniles. Four diets were formulated, replacing FM with HM at 0%, 22%, 60%, and 100% levels, corresponding to an inclusion level of 15 (diet HM15), 30 (diet HM30), and 45% (diet HM45), respectively. Over 67 days, fish were fed these diets until apparent visual satiation. Results showed no significant differences in immune parameters or hematological profiles, except for a decrease in hemoglobin and hematocrit levels. In the liver, glucose-6-phosphate dehydrogenase and glutathione peroxidase decreased linearly with HM content, especially at 100% replacement. Glutathione reductase activity was also reduced with HM inclusion, being lower in fish fed diet HM30 compared to the control. Fish fed diet HM15 showed lower hepatic superoxide dismutase activity, while catalase activity and lipid peroxidation remained unaffected. In the intestine, antioxidant enzyme activity was not influenced by HM, but lipid peroxidation linearly decreased with HM inclusion, being lower in the HM30 diet compared to the control. The inclusion of HM reduced the expression of intestinal pro-inflammatory genes (interleukin-1β and cyclooxygenase-2) while the expression of transforming growth factor β was higher in fish fed diet HM30 compared to the control and HM45 diets. In conclusion, up to 45% dietary inclusion of HM showed no adverse effects, improving liver antioxidant status, reducing intestinal oxidative stress, and regulating inflammatory gene expression.

Chitin, chitosan and chitooligosaccharides as potential growth promoters and immunostimulants in aquaculture: A comprehensive review

There is a stable growth in aquaculture production to avoid seafood scarcity. The usage of eco-friendly feed additives is not only associated with aquatic animal health but also reduces the risk of deleterious effects to the environment and consumers. Aquaculture researchers are seeking dietary solutions to improve the growth performance and yield of target organisms. A wide range of naturally derived compounds such as probiotics, prebiotics, synbiotics, complex carbohydrates, nutritional factors, herbs, hormones, vitamins, and cytokines was utilized as immunostimulants in aquaculture. The use of polysaccharides derived from natural resources, such as alginate, agar, laminarin, carrageenan, fucoidan, chitin, and chitosan, as supplementary feed in aquaculture species has been reported. Polysaccharides are prebiotic substances which are enhancing the immunity, disease resistance and growth of aquatic animals. Further, chitin (CT), chitosan (CTS) and chitooligosaccharides (COS) were recognized for their biodegradable properties and unique biological functions. The dietary effects of CT, CTS and COS at different inclusion levels on growth performance, immune response and gut microbiota in aquaculture species has been reviewed. The safety regulations, challenges and future outlooks of CT, CTS and COS in aquatic animals have been discussed in this review.

Repurposing chitin-rich seafood waste for warm-water fish farming

The pisciculture industry has grown multi-fold over the past few decades. However, a surge in development and nutrient demand has led to the establishment of numerous challenges. Being a potential solution, chitosan has gained attention as a bio nanocomposite for its well-acclaimed properties including biodegradability, non-toxicity, immunomodulatory effects, antimicrobial activity, and biocompatibility. This biopolymer and its derivatives can be transformed into various structures, like micro and nanoparticles, for various purposes. Consequently, with regards to these properties chitin and its derivatives extend their application into drug delivery, food supplementation, vaccination, and preservation. This review focuses on the clinical advancements made in fish biotechnology via chitosan and its derivatives and highlights its prospective expansion into the pisciculture industry-in particular, warm-water species.

Integrated transcriptomic and metabolomic analysis sheds new light on adaptation of Pinctada fucata martensii to short-term hypoxic stress

Analyses of the transcriptome and metabolome were conducted to clarify alterations of key genes and metabolites in pearl oysters following exposure to short-term hypoxic treatment. We totally detected 209 DEGs between the control and hypoxia groups. Enrichment analysis indicated the enrichment of GO terms including "oxidation-reduction process", "ECM organization", "chaperone cofactor-dependent protein refolding", and "ECM-receptor interaction" KEGG pathway by the DEGs. In addition, between the two groups, a total of 28 SDMs were identified, which were implicated in 13 metabolic pathways, such as "phenylalanine metabolism", "D-amino acid metabolism", and "aminoacyl-tRNA biosynthesis". Results suggest that pearl oysters are exposed to oxidative stress and apoptosis under short-term hypoxia. Also, pearl oysters might adapt to short-term hypoxic treatment by increasing antioxidant activity, modulating immune and biomineralization activities, maintaining protein homeostasis, and reorganizing the cytoskeleton. The results of our study help unveil the mechanisms by which pearl oysters respond adaptively to short-term hypoxia.

Growth and Welfare of Rainbow Trout (Oncorhynchus mykiss) in Response to Graded Levels of Insect and Poultry By-Product Meals in Fishmeal-Free Diets

This study compared the nutrient-energy retention, digestive function, growth performance, and welfare of rainbow trout (ibw 54 g) fed isoproteic (42%), isolipidic (24%), fishmeal-free diets (CV) over 13 weeks. The diets consisted of plant-protein replacement with graded levels (10, 30, 60%) of protein from poultry by-product (PBM) and black soldier fly H. illucens pupae (BSFM) meals, either singly or in combination. A fishmeal-based diet was also tested (CF). Nitrogen retention improved with moderate or high levels of dietary PBM and BSFM relative to CV (p < 0.05). Gut brush border enzyme activity was poorly affected by the diets. Gastric chitinase was up-regulated after high BSFM feeding (p < 0.05). The gut peptide and amino acid transport genes were differently regulated by protein source and level. Serum cortisol was unaffected, and the changes in metabolites stayed within the physiological range. High PBM and high BSFM lowered the leukocyte respiratory burst activity and increased the lysozyme activity compared to CV (p < 0.05). The BSFM and PBM both significantly changed the relative percentage of lymphocytes and monocytes (p < 0.05). In conclusion, moderate to high PBM and BSFM inclusions in fishmeal-free diets, either singly or in combination, improved gut function and nutrient retention, resulting in better growth performance and the good welfare of the rainbow trout.

The effects of dietary immunostimulants on the innate immune response of Indian major carp: A review

Immunostimulants, as feed additives, play an important role in maintaining fish health and enhancing their overall growth by providing resistance against diseases in cultured fish. At the initial stages of life of fish, innate immunity is the essential mechanism in their survival. Later, innate immunity has an instructive role in adapting acquired immune response and homeostasis through different receptor proteins. Several studies have been conducted to analyze the effect of dietary immunostimulants like algae, plant extracts, vitamins, herbs, probiotics, and prebiotics-containing diets in Indian major carps. Many bacterial, fungal and viral pathogens are responsible for high death rates in both wild and cultured fish. It's a major limiting factor for world aquaculture industries. Recognition of invading pathogens by different pathogen recognition receptor plays an important role for the activation of different pathways to initiate protective immune responses. Hence, there is a growing need to control the devastating effects of diseases without recourse to toxic chemicals or antibiotics. Keeping with alternative approaches without using toxic chemicals to control fish diseases in mind, many immunostimulants are used, which enhance immune responses along with their gene expression level through different signaling pathway. The objective of this review is to summarize and evaluate the current knowledge of various immunostimulants and their immune responses in three Indian major carps namely Catla catla, Labeo rohita and Cirrhinus mrigala, which are preferred by the people.

Effects of dietary silkrose of Antheraea yamamai on gene expression profiling and disease resistance to Edwardsiella tarda in Japanese medaka (Oryzias latipes)

We previously identified a novel acidic polysaccharide, silkrose-AY, from the Japanese oak silkmoth (Antheraea yamamai), which can activate an innate immune response in mouse macrophage cells. However, innate immune responses stimulated by silkrose-AY in teleosts remain unclear. Here, we show the influence of dietary silkrose-AY in medaka (Oryzias latipes), a teleost model, in response to Edwardsiella tarda infection. Dietary silkrose-AY significantly improved the survival of fish and decreased the number of bacteria in their kidneys after the fish were artificially infected with E. tarda by immersion. We also performed a microarray analysis of the intestine, which serves as a primary barrier against microbial infection, to understand the profiles of differentially expressed genes (DEGs) evoked by silkrose-AY. The dietary silkrose-AY group showed differential expression of 2930 genes when compared with the control group prior to E. tarda infection. Gene ontology and pathway analysis of the DEGs highlighted several putative genes involved in pathogen attachment/recognition, the complement and coagulation cascade, antimicrobial peptides/enzymes, opsonization/phagocytosis, and epithelial junctional modification. Our findings thus provide fundamental information to help understand the molecular mechanism of bacterial protection offered by insect-derived immunostimulatory polysaccharides in teleosts.

The Feasibility of Using Yellow Mealworms (Tenebrio molitor): Towards a Sustainable Aquafeed Industry

Simple Summary

The expansion of the aquaculture industry depends mainly on aquafeed availability at reasonable prices. The common ingredients of aquafeed (e.g., fish and soybean meals) are not sustainable due to a lack of resources and increasing prices. Seeking alternative non-traditional ingredients is among the choices of nutritionists to produce high-quality feed at a feasible cost. Yellow mealworms (Tenebrio molitor) (TM) have been introduced to the feed industry as protein sources of a circular economy. Many studies have investigated the possibility of including T. molitor meals as a substitute for fish and soybean meals in aquafeed. Thus, this review exclusively presents an assemblage of the literature on the possibility of including T. molitor in aquafeed as a suggestion for the sustainability of the aquaculture industry.

Abstract

The success of the aquafeed industry mainly depends on the availability of raw ingredients with high nutritional value, such as fishmeal (FM). However, the increased demand for FM elevates its prices and leads to high feed costs. Thus, there is an urgent need to find suitable alternatives for FM in fish diets to achieve sustainability in aquaculture. Currently, attention is being paid to the possibility of using insect meals as FM substitutes in aquafeed because of their relatively high nutritional quality. TM is one of those insects that can be regarded as a unique candidate because of its relatively high nutritional value. TM are rich sources of essential amino acids (methionine), lipids, and fatty acids, which vary based on the developmental stage of the worms. Although TM have an abundant amount of chitin as a fiber source and other anti-nutritional factors, numerous studies have investigated the efficacy of partial or complete substitution of FM by T. molitor in fish diets. In this context, we reviewed the current research findings on the achievable inclusion levels of T. molitor versus FM substitution in the diets of several finfish and shellfish species. We discussed the potential use of T. molitor as an FM substitute in fish diets and evaluated its effects on growth, biometric indices, and body composition. Besides, the hematological parameters, immunological responses, antioxidative efficacy, intestinal health status, and sensory criteria of fish fed T. molitor-based diets were also assessed.

Dietary Inclusion of Black Soldier Fly (Hermetia Illucens) Larvae Meal and Paste Improved Gut Health but Had Minor Effects on Skin Mucus Proteome and Immune Response in Atlantic Salmon (Salmo Salar)

The present study investigated effects of dietary inclusion of black soldier fly larvae (BSFL) (Hermetia illucens) meal and paste on gut health, plasma biochemical parameters, immune response and skin mucus proteome in pre-smolt Atlantic salmon (Salmo salar). The seven-week experiment consisted of seven experimental diets: a control diet based on fishmeal and plant protein (Control-1); three BSFL meal diets, substituting 6.25% (6.25IM), 12.5% (12.5IM) and 25% (25IM) of protein; two BSFL paste diets, substituting 3.7% (3.7IP) and 6.7% (6.7IP) of protein and an extra control diet with 0.88% of formic acid (Control-2). The 6.25IM diet reduced enterocyte steatosis in pyloric caeca, improved distal intestine histology, and reduced IgM in distal intestine. The fish fed 12.5IM diet reduced enterocyte steatosis in pyloric caeca, improved distal intestine histology, had a higher plasma lysozyme content compared to 6.25IM, and tend to increase phagocytic activity in head-kidney macrophages-like cells. On the other hand, 25IM diet improved distal intestine histology, but showed mild-moderate enterocyte steatosis in pyloric caeca, increased IFNγ and reduced IgM in distal intestine. In the case of BSFL paste diets, 3.7IP diet caused mild inflammatory changes in distal intestine, although it reduced enterocyte steatosis in pyloric caeca. The 6.7IP diet reduced enterocyte steatosis in pyloric caeca and improved distal intestine histology. Increasing level of BSFL meal in the diet linearly decreased plasma C-reactive protein, whereas increasing level of BSFL paste linearly increased plasma antioxidant capacity. Dietary inclusion of BSFL meal and paste had minor effects on the expression profile of proteins in skin mucus and no effects on immune markers in splenocytes. BSFL meal showed no negative effect on liver and muscle health as indicated by plasma alanine aminotranseferase, asparate aminotransferase and creatine kinase. The present study showed that replacing conventional protein sources with low to moderate levels of BSFL meal (6.25% and 12.5%) or paste (3.7% and 6.7%) reduced enterocyte steatosis in pyloric caeca, while replacing up to 25% with BSFL meal or 6.7% with paste improved distal intestine histology. Further, dietary inclusion of BSFL meal and paste had minor effects on skin mucus proteome and immune response in Atlantic salmon.

Chitosan and chitooligosaccharides attenuate soyabean meal-induced intestinal inflammation of turbot (Scophthalmus maximus): possible involvement of NF-кB, activator protein-1 and mitogen-activated protein kinases pathways

An 8-week feeding experiment was conducted to investigate and confront the putative functions of chitosan (CTS) and chitooligosaccharide (COS) in the growth and homoeostasis of distal intestine in juvenile turbots fed diets containing soyabean meal (SBM). Three isolipidic and isonitrogenous diets were formulated by supplemented basal diet (based on a 400 g/kg SBM) with 7·5 g/kg CTS or with 2·0 g/kg COS. Our results indicated that both CTS and COS supplementation could significantly improve (i) the growth performance and feed efficiency ratio; (ii) antioxidant activity driven by metabolic enzymes (i.e. catalase, glutathione reductase, glutathione peroxidase and superoxide dismutase); (iii) glutathione levels; (iv) acid phosphatase and lysozyme activity and (v) IgM content. As a result, these two particular prebiotics were able to significantly attenuate the histological alterations due to local inflammation as well as to decrease the transcriptional levels of proinflammatory cytokines (i.e. IL-1β, IL-8 and TNF-α) and major pathway effectors (i.e. activator protein-1 (AP-1), NF-кB, p38 mitogen-activated protein kinase, c-Jun N-terminal kinase and extracellular regulated kinase). High-throughput sequencing data indicated that dietary CTS and COS could significantly decrease the diversity of intestinal bacteria but elevate the relative abundances of Bacillus, Lactobacillus and Pseudomonas genera. Altogether, these findings suggest that CTS and COS can improve growth of turbot, enhance intestinal immune and anti-oxidant systems and promote the balance of intestinal microbiota. The protective effects, elicited by these two prebiotics, against SBM-induced inflammation could be attributed to their roles in alleviating the overexpression of inflammatory cytokines by possibly down-regulating NF-кB, AP-1 and/or mitogen-activated protein kinases pathways.

Chitosan-Based Drug Delivery System: Applications in Fish Biotechnology

Chitosan is increasingly used for safe nucleic acid delivery in gene therapy studies, due to well-known properties such as bioadhesion, low toxicity, biodegradability and biocompatibility. Furthermore, chitosan derivatization can be easily performed to improve the solubility and stability of chitosan-nucleic acid polyplexes, and enhance efficient target cell drug delivery, cell uptake, intracellular endosomal escape, unpacking and nuclear import of expression plasmids. As in other fields, chitosan is a promising drug delivery vector with great potential for the fish farming industry. This review highlights state-of-the-art assays using chitosan-based methodologies for delivering nucleic acids into cells, and focuses attention on recent advances in chitosan-mediated gene delivery for fish biotechnology applications. The efficiency of chitosan for gene therapy studies in fish biotechnology is discussed in fields such as fish vaccination against bacterial and viral infection, control of gonadal development and gene overexpression and silencing for overcoming metabolic limitations, such as dependence on protein-rich diets and the low glucose tolerance of farmed fish. Finally, challenges and perspectives on the future developments of chitosan-based gene delivery in fish are also discussed.

Study the immunomodulation of anthracenedione in striped dwarf catfish, Mystus vittatus against pathogenic bacteria, Aeromonas hydrophila

Anthracenedione is a derivative of anthraquinone aromatic organic natural pigments found in senna, aloe latex, rhubarb, cascara, lichens, and fungi having broad range of bioactivity, including anti-cancer, anti-inflammatory, anti-microbial, anti-fungal, anti-oxidant, anti-viral activities suggesting potential for clinical purpose of many diseases. The effect of anthracenedione enriched diet on growth, hematology, innate and adaptive immune parameters as well as protection from Aeromonas hydrophila in Mystus vittatus was reported. The weight gain, feed intake, specific growth rate (SGR), and feed conversion ratio (FCR) were significantly increased in uninfected groups fed with 5 mg kg^-1 diet. The red blood cells (RBC) and white blood cells (WBC) count and the percentage of lymphocytes were significantly augmented in both infected and uninfected groups feeding with any diet. The percentage of monocytes, eosinophils, neutrophils and the biochemical profile such as total protein, albumin, and globulin also were significantly increased in the infected and uninfected groups fed with 5 mg kg^-1 enriched diet. The innate and adaptive immune parameters such as phagocytic activity, immunoglobulin M (IgM), respiratory burst activity, complement activity, and lysozyme activity were significantly increased in uninfected and infected groups fed with 5 or 10 mg kg^-1 diets but not with 1 mg kg^-1 diet. The serum superoxide dismutase (SOD) activity is significantly increased in the uninfected and infected fish fed with 5 mg kg^-1 diet but the increase was not significantly observed in 1 or 10 mg kg^-1 diets. The nitric oxide (NO) production is significantly elevated in both uninfected and infected groups fed with 5 mg kg^-1 diet. On the other hand, the lymphocyte proliferation and myeloperoxidase (MPO) activity were significantly increased the infected and uninfected groups fed with 5 and 10 mg kg^-1 diets. The cumulative mortality was found 5% with 1 and 5 mg kg^-1 diet groups while it was observed 10% mortality with 10 mg kg^-1 diet group. Based on the results, it is observed that feeding the uninfected and infected groups with 5 mg kg^-1 anthracenedione diet resulted in better improvement of growth, hematological, biochemical, and innate as well as adaptive immune parameters in M. vittatus against A. hydrophila.

Recent progress in biomedical applications of chitosan and its nanocomposites in aquaculture: A review

Chitosan nanoparticles (CSNPs) are the nanostructures of chitosan biopolymer which is derived from chitin polysaccharide, the main component of crustacean shells. Chitosan is a biocompatible, nontoxic and biodegradable polymer soluble in acidic solutions and easily excreted from kidneys. It is widely used in medical and pharmaceutical applications including artificial matrices for tissue engineering, drug transport, targeted drug delivery and protein or gene delivery. The antimicrobial activities of chitosan and CSNPS against different bacterial, fungal and viral pathogens made them valuable for several biological applications including food preservation purposes. In addition, they have immunomodulatory effects on fish and crustaceans providing direct positive impact on aquaculture and fish farming industry. Sustained release of some bioactive ingredients such as hormones, vitamins, nutrients and antioxidants has improved the biological activities of fish. Furthermore, CSNPs have recently been employed to diagnose fish diseases. In this review, we present the medical and biological applications of chitosan and CSNPs on aquatics to provide an update on recent advances and the potential for further advanced applications for aquaculture in the future.

Immunostimulatory effect of dietary chitosan nanoparticles on the performance of Nile tilapia, Oreochromis niloticus (L.)

Feed supplements to fish are generally used to overcome any expected diseases and stressors and to sustain eco-friendly fish farming. One of these feed supplements is chitosan, which stimulated growth and immune properties for many aquatic organisms. It is expected that the nano-sized materials may have stronger immune activation in fish than the ordinary size. Therefore, the current study was conducted to evaluate the effect of dietary chitosan nanoparticles (CNP) on growth performance, antioxidant activity, and innate immunity of Nile tilapia, Oreochromis niloticus (L.). Fish (19.8 ± 0.59 g) were fed on diets enriched with 0.0, 0.25, 0.5, 1.0, and 2.0 g CNP/kg diet for 45 days. Fish performance was significantly improved with increasing CNP levels over the control diet with optimum level of 1.0 g CNP/kg diet. Antioxidant-stimulated activity was observed due to dietary CNP supplementation over the control diet in a dose-dependent manner. However, malondialdehyde level decreased significantly, whereas activities of catalase, superoxide dismutase, lysozyme, and respiratory burst increased significantly due to CNP supplementation in a dose-dependent manner. The current study evoked that dietary CNP showed strong immune modulatory properties and enhanced significantly the performance and health of Nile tilapia with optimum level of 1.0 g CNP/kg diet.

Epizootic ulcerative syndrome causes cutaneous dysbacteriosis in hybrid snakehead (Channa maculata♀ × Channa argus♂)

Cutaneous microbiota play an important role in protecting fish against pathogens. Aphanomyces infection causes epizootic ulcerative syndrome (EUS) in fish, and by perturbing the integrity of the cutaneous microbiota, increases the potential for infection by pathogenic bacteria. However, whether the composition of the cutaneous microbiota is altered in fish with EUS, and if so, which species are changed and how this might influence infected fish, is still largely unclear. Considering the importance of cutaneous microbiota in maintaining host health, we hypothesized that Aphanomyces infection significantly enhances the presence of certain bacterial pathogens in the cutaneous microbiota and causes cutaneous dysbacteriosis. To test this hypothesis, we compared the cutaneous microbiota compositions of hybrid snakehead (Channa maculata♀ × Channa argus♂) with and without Aphanomyces infection using Illumina Miseq sequencing of the 16S rRNA gene. Our results showed that the cutaneous microbiota of hybrid snakehead were significantly altered subsequent to EUS infection and that the numbers of potentially pathogenic bacteria classified into the genera Anaerosinus, Anaerovorax, Dorea, and Clostridium were significantly enhanced in the cutaneous microbiota of hybrid snakehead with EUS, whereas bacteria classified into the genera Arthrobacter, Dysgonomonas, Anoxybacillus, Bacillus, Solibacillus, Carnobacterium, Lactococcus, Streptococcus, Achromobacter, Polynucleobacter, Vogesella, and Pseudomonas were significantly reduced. These results imply that treatment for EUS should not only take into consideration the control of Aphanomyces reproduction but should also focus on regulating the cutaneous microbiota of infected fish.

Application of marine-derived polysaccharides as immunostimulants in aquaculture: A review of current knowledge and further perspectives

The use of antibiotics in the feeds of cultivable aquatic animals has been generally practised to reduce infectious diseases as well as to improve the survival and growth. In recent years, many countries ban to aquatic animals due to the use of large amount of antibiotics and chemotherapies, thus alternative novel strategies are need to promote the growth of aquatic animals and control the pathogens. Dietary supplementation of marine-derived polysaccharides (MDPs) is one of the potential substitutes for antibiotics in aquatic animal feeds. Recently, the use of dietary MDPs in the aquaculture animals has been focused with much interest. In aquaculture, MDPs are used as prebiotic substance which is mostly accepted as a nutritional component for improving the growth performance and health conditions. Hence, present review is a comprehensive and an updated collection of available research reports on different MDPs (alginate, fucoidan, carrageenan, laminarin, ulvan, galactan, agar, chitin and chitosan), route of administration, dosage and applications for improving aqua feeds with emphasis on its effects on growth, biochemical indices, immune response, gut microbiota and disease resistance of aquaculture animals. This review describes the sustainability of global aquaculture production by providing a best alternative to harmful antibiotics, thereby meeting the emerging consumer demand for antibiotic-free aquatic food products.

Use of Organic Wastes and Industrial By-Products to Produce Filamentous Fungi with Potential as Aqua-Feed Ingredients

Organic-rich waste and industrial by-product streams, generated in enormous amounts on a daily basis, contain substantial amounts of nutrients that are worthy of recovery. Biological conversion of organic-waste streams using filamentous fungi is a promising approach to convert nutrients into value-added bioproducts, such as fungal biomass. High-protein fungal biomass contains different kinds and levels of amino acids, fatty acids, immunostimulants, antioxidants, pigments, etc., which make it a potential choice for application in animal feed supplementation. Considering the challenges long faced by the aquaculture industry in fishmeal production due to the increasing prices and environmental concerns, the aquaculture industry is forced to provide alternative protein-rich sources to replace conventional fishmeal. In this review, the possibilities of utilization of filamentous fungi biomass cultivated on organic-rich waste streams, as an alternative nutrient source in fish feed, were thoroughly reviewed.

Effects of dietary Tenebrio molitor meal on the growth performance, immune response and disease resistance of yellow catfish (Pelteobagrus fulvidraco)

This study evaluated the influence of diets containing mealworm (Tenebrio molitor) meal in partial substitution of fishmeal on growth performance and immune responses of juvenile yellow catfish (Pelteobagrus fulvidraco). Four diets were formulated to contain 0 (the control diet), 9, 18 and 27 g mealworm meal per 100 g diet with 0%, 25%, 50% and 75% of fishmeal replacement, respectively. Yellow catfish were randomly divided into 4 groups with 3 replicates in each group. The fish in each group were fed with one of the four experimental diets for 5 weeks. Growth performance, plasma parameters (SOD, MDA, IgM, C3, lysozyme) and immune related genes (MHC II, IL-1, CypA, IgM, HE) of yellow catfish were determined at the end of the feeding trial, as well as 24 h post bacterial (Edwardsiella ictaluri) challenge. The present results showed that dietary inclusion of mealworm meal (MW) had no negative effects on the growth performance of the juvenile yellow catfish, compared to the control group. At the end of the feeding trial, plasma MDA contents of MW supplemented groups were significant lower than the control group. Plasma SOD activities increased significantly with the increasing dietary MW contents at the end of feeding trial (pre-challenge) and 24 h post challenge with E. ictaluri. Significant increase of plasma lysozyme activity was found in MW supplemented groups compared to the control group 24 h post bacterial challenge. Plasma IgM levels increased significantly with the increasing dietary MW contents at the end of feeding trial. Compared with the control group, the immune related genes of MHC II, IL-1, IgM and HE of the fish in the MW supplemented groups significantly upregulated pre-challenge or 24 h post bacterial challenge. Finally, it was observed that the survival rate of the 27% MW group was significant higher (P < 0.05) than the control group but was not significantly differed from the 18% MW group. The present results indicated that dietary inclusion level of at least 18% MW could improve the immune response and the bacterial resistance of yellow catfish without any negative growth effects.

Nanodelivery Systems as New Tools for Immunostimulant or Vaccine Administration: Targeting the Fish Immune System

Fish disease treatments have progressed significantly over the last few years and have moved from the massive use of antibiotics to the development of vaccines mainly based on inactivated bacteria. Today, the incorporation of immunostimulants and antigens into nanomaterials provide us with new tools to enhance the performance of immunostimulation. Nanoparticles are dispersions or solid particles designed with specific physical properties (size, surface charge, or loading capacity), which allow controlled delivery and therefore improved targeting and stimulation of the immune system. The use of these nanodelivery platforms in fish is in the initial steps of development. Here we review the advances in the application of nanoparticles to fish disease prevention including: the type of biomaterial, the type of immunostimulant or vaccine loaded into the nanoparticles, and how they target the fish immune system.

Assessment of the immune-modulatory and antimicrobial effects of dietary chitosan on Nile tilapia (Oreochrmis niloticus) with special emphasis to its bio-remediating impacts

Fish, pathogen and environment are three counterparts who are sharing the same circle of life. To keep fish up to their optimal health, environment should be competently improved and pathogen count/virulence should be seized. Using of bioactive immunostimulants to achieve these objectives is the hypothesis under assessment. Thus, the present study was performed to evaluate the use of shrimp shells derived chitosan as an immunostimulant as well as preventive regime against Aeromonas hydrophila infection of Nile tilapia and to assess its antibacterial/aquatic bio-remediating effects. Results achieved by feeding 1% chitosan as preventive/therapeutic regimes have revealed a remarkably enhanced several innate immunological parameters (e.g., Phagocytic activity/index, NBT, Lysozyme activity and ACH50), increased resistance against A. hydrophila and strikingly improved water quality compared to the 0.5 and 2% chitosan containing diets. Conclusively, experimental results suggest the commercial usage of chitosan as an efficient immunostimulant and bio-remediating agent in aquaculture.

Improvement in non-specific immunity and disease resistance of barramundi, Lates calcarifer (Bloch), by diets containing Daphnia similis meal

A 42-day study was conducted with barramundi, Lates calcarifer, to evaluate the effects of Daphnia meal derived from Daphnia similis on fish growth, immune response, and disease resistance to Aeromonas hydrophila. Three isonitrogenous (45%) and isolipid (10%) experimental diets were formulated to contain 0% (control), 5% (D5), and 10% (D10) Daphnia meal. Growth was depressed when fish were fed with the D10 diet for 42 days compared to control. However, the growth in fish fed with control and D5 diets for 42 days was not significantly different. By day 42, the leukocyte phagocytic activity and respiratory burst activity were significantly increased in D5 and D10 groups compared to control. Mx gene expression in the spleen and head kidney of fish after being injected with nerve necrosis virus was also significantly up-regulated in both groups compared to control. In an increased immune response, D5 and D10 fish had significantly higher survival rates than control after being challenged by A. hydrophila. Therefore, we suggest that a 5% Daphnia-meal diet could improve the barramundi immune response and disease resistance without a negative impact on growth.