Effect of dietary chitosan on growth performance, hematological parameters, intestinal histology and stress resistance of Caspian kutum (Rutilus frisii kutum Kamenskii, 1901) fingerlings

Effect of dietary chitosan on the growth performance, intestinal histology and growth-related gene expression in stellate sturgeon (Acipenser stellatus) juveniles

As sturgeon breeding has proliferated, there has been a heightened demand for growth stimulators in their diets. This study aimed to determine the impact of dietary chitosan on growth performance, whole-body proximate composition, growth-related gene expression, and intestinal histology in juvenile Acipenser stellatus. A total of 180 A. stellatus juveniles with an average weight of 31.90 ± 0.73 g were fed with diets containing 0 (control), 1.5, 3.0, 4.5, and 6.0 g chitosan.kg-1 basic diet for eight weeks. The findings revealed a significant enhancement in growth performance with rising chitosan concentrations. Furthermore, chitosan supplementation upregulated the expression of the growth hormone gene in both brain and liver tissues. In liver samples, the most pronounced expression of the insulin-like growth factor-1 gene was noted at 6.0 g chitosan.kg-1, while in brain samples, peak expressions were observed in both the 4.5 and 6.0 g chitosan.kg-1 treatments. While the whole-body proximate composition remained relatively stable, there was a notable decrease in whole-body lipids with the escalation of chitosan dosage. Intestinal villi dimensions, both height and width, were amplified in the chitosan-supplemented groups compared to controls. In summation, chitosan supplementation showed promise in bolstering growth performance, refining intestinal morphology, and enhancing growth-related gene expression. Analysis of the polynomial regression of weight gain and specific growth rate revealed that the optimum dietary chitosan requirements in A. stellatus were 5.32 and 5.21 g chitosan.kg-1, respectively.

Dietary Chitosan Attenuates High-Fat Diet-Induced Oxidative Stress, Apoptosis, and Inflammation in Nile Tilapia (Oreochromis niloticus) through Regulation of Nrf2/Kaep1 and Bcl-2/Bax Pathways

Fatty liver injury is a prevalent condition in most farmed fish, yet the molecular mechanisms underpinning this pathology remain largely elusive. A comprehensive feeding trial spanning eight weeks was conducted to discern the potential of dietary chitosan in mitigating the deleterious effects of a high-fat diet (HFD) while concurrently exploring the underlying mechanism. Growth performance, haemato-biochemical capacity, antioxidant capacity, apoptotic/anti-apoptotic gene expression, inflammatory gene expression, and histopathological changes in the liver, kidney, and intestine were meticulously assessed in Nile tilapia. Six experimental diets were formulated with varying concentrations of chitosan. The first three groups were administered a diet comprising 6% fat with chitosan concentrations of 0%, 5%, and 10% and were designated as F6Ch0, F6Ch5, and F6Ch10, respectively. Conversely, the fourth, fifth, and sixth groups were fed a diet containing 12% fat with chitosan concentrations of 0%, 5%, and 10%, respectively, for 60 days and were termed F12Ch0, F12Ch5, and F12Ch10. The results showed that fish fed an HFD demonstrated enhanced growth rates and a significant accumulation of fat in the perivisceral tissue, accompanied by markedly elevated serum hepatic injury biomarkers and serum lipid levels, along with upregulation of pro-apoptotic and inflammatory markers. In stark contrast, the expression levels of nrf2, sod, gpx, and bcl-2 were notably decreased when compared with the control normal fat group. These observations were accompanied by marked diffuse hepatic steatosis, diffuse tubular damage, and shortened intestinal villi. Intriguingly, chitosan supplementation effectively mitigated the aforementioned findings and alleviated intestinal injury by upregulating the expression of tight junction-related genes. It could be concluded that dietary chitosan alleviates the adverse impacts of an HFD on the liver, kidney, and intestine by modulating the impaired antioxidant defense system, inflammation, and apoptosis through the variation in nrf2 and cox2 signaling pathways.

Effects of Shrimp Shell-Derived Chitosan on Growth, Immunity, Intestinal Morphology, and Gene Expression of Nile Tilapia (Oreochromis niloticus) Reared in a Biofloc System

Chitosan (CH) shows great potential as an immunostimulatory feed additive in aquaculture. This study evaluates the effects of varying dietary CH levels on the growth, immunity, intestinal morphology, and antioxidant status of Nile tilapia (Oreochromis niloticus) reared in a biofloc system. Tilapia fingerlings (mean weight 13.54 ± 0.05 g) were fed diets supplemented with 0 (CH0), 5 (CH5), 10 (CH10), 20 (CH20), and 40 (CH40) mL·kg-1 of CH for 8 weeks. Parameters were assessed after 4 and 8 weeks. Their final weight was not affected by CH supplementation, but CH at 10 mL·kg-1 significantly improved weight gain (WG) and specific growth rate (SGR) compared to the control (p < 0.05) at 8 weeks. Skin mucus lysozyme and peroxidase activities were lower in the chitosan-treated groups at weeks 4 and 8. Intestinal villi length and width were enhanced by 10 and 20 mL·kg-1 CH compared to the control. However, 40 mL·kg-1 CH caused detrimental impacts on the villi and muscular layer. CH supplementation, especially 5-10 mL·kg-1, increased liver and intestinal expressions of interleukin 1 (IL-1), interleukin 8 (IL-8), LPS-binding protein (LBP), glutathione reductase (GSR), glutathione peroxidase (GPX), and glutathione S-transferase (GST-α) compared to the control group. Overall, dietary CH at 10 mL·kg-1 can effectively promote growth, intestinal morphology, innate immunity, and antioxidant capacity in Nile tilapia fingerlings reared in biofloc systems.

Prophylactic and Therapeutic Efficacy of Ultrasonicated Rosmarinus officinalis Ethanolic Extract and its Chitosan-Loaded Nanoparticles Against Eimeria tenella Infected Broiler Chickens

PURPOSE

The in vivo efficacy of ultrasonicated Rosmarinus officinalis ethanolic extract (UROEE) and its chitosan-loaded nanoparticles (UROEE-CsNPs) was investigated as a dietary prophylactic agent and as a therapeutic treatment against Eimeria tenella infected broiler chickens.

METHODS

Chickens were infected with 4 × 104 E. tenella oocysts at 21 days old for primary infection and with 8 × 104 oocysts at 35 days old for secondary infection. Eleven experimental groups were conducted. Dietary addition of 100 mg/kg UROEE and 20 mg/kg for CsNPs as well as UROEE-CsNPs were included for prophylactic groups from day 1 to 42. The same doses were used for therapeutic treatment groups for 5 constitutive days. Oocyst output in feces was counted. Histopathological and immunohistochemical studies were conducted. Gene expression of pro-inflammatory cytokines as IFN-γ, IL-1β and IL-6 as well as anti-inflammatory cytokines as IL-10 and TGF-β4 was analyzed using semi-quantitative reverse transcriptase-PCR.

RESULTS

The results showed an efficacy of UROEE, CsNPs and UROEE-CsNPs in reduction of oocyst excretion and improving the cecal tissue architecture. CD4+ and CD8+ T lymphocytes protein expression were reduced. E. tenella infection lead to upregulation of pro-inflammatory cytokines as IFN-γ, IL-1β, IL-6 and anti-inflammatory cytokines as TGF-β4 following primary infection, while their expression was downregulated following secondary infection.

CONCLUSION

The dietary prophylactic additives and therapeutic treatments with UROEE, CsNPs and UROEE-CsNPs could decrease the inflammatory response to E. tenella as indicated by oocyst output reduction, histopathological improvements, CD4+ and CD8+ T cells protein expression reduction as well as reducing mRNA expression levels of the tested cytokines following primary and secondary infections. Consequently, these results will help to develop better-combating strategies for the control and prevention of coccidiosis on poultry farms as a dietary prophylactic agent or as a therapeutic treatment.

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.

Long-Term Application of a Synbiotic Chitosan and Acinetobacter KU011TH Mixture on the Growth Performance, Health Status, and Disease Resistance of Hybrid Catfish (Clarias gariepinus × C. macrocephalus) during Winter

The effects of potential synbiotic chitosan and Acinetobacter KU011TH mixture on growth performance, immune response, and A. hydrophila resistance were investigated for the first time. The control group was fed a basal diet (A), and group B was given the formula B diet that was supplemented with chitosan at 20 mL/kg diet via top dressing. The other synbiotic groups, C, D, and E, were top-dressed with the target probiotics at 1 × 10⁸, 1 × 10⁹, and 1 × 10¹⁰ CFU/kg diet, respectively, and coated with the same concentration of chitosan. Fish were continuously fed the five different feeds for 16 weeks during winter. At the end of the trial, the growth parameters of the test groups did not significantly differ from those of the control (p > 0.05). All the symbiotic-chitosan treatments significantly increased various hematological and serum immune parameters. Moreover, the expression levels of immune-related genes were strongly elevated in the head kidney and spleen, whereas upregulated expression was observed in the liver and whole blood (p < 0.05). Survival analysis indicated that fish in groups B and C showed significantly higher survival (84.33 ± 2.21 and 79.50 ± 6.34%) than those in groups A, D and E (55.33 ± 8.82%-74.00 ± 6.50) (p < 0.05) after injection with A. hydrophila for 14 days.

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.

Dietary chitosan moderates the growth rate, antioxidant activity, immunity, intestinal morphology and resistance against Aeromonas hydrophila of juvenile hybrid sturgeon (Acipenser baerii♀ × Acipenser schrenckii♂)

This study investigated the effects of dietary chitosan on growth, antioxidant, immunity, intestinal morphology and resistance against Aeromonas hydrophila of hybrid sturgeon (Acipenser baerii♀ × Acipenser schrenckii♂). Sturgeons (18.18 ± 0.08 g) were randomly divided into four groups, fed with chitosan-supplemented diets for 8 weeks and then infected with A. hydrophila. The results showed significant differences of body weight gain, specific growth rate and feed conversion ratio in sturgeon fed chitosan and control diets. The oral administration of chitosan significantly increased the acid phosphatase, alkaline phosphatase, lysozyme, myeloperoxidase, superoxide dismutase, glutathione peroxidase and catalase activities, as well as the complement 3 and 4 contents and disease resistance against A. hydrophila. Moreover, enhancement of muscular thickness and goblet cells in mid intestine and increase of muscular thickness and villus height in spiral valve were observed in the chitosan supplemented groups. In addition, dietary chitosan-supplemented diets mitigated the changes of antioxidant and immune activity induced by A. hydrophila challenge, as well as prevented fish from bacterial invasion. The optimal dose was 3.00 g chitosan/kg diet for hybrid sturgeon.

Dietary chitosan modulates the growth performance, body composition and nonspecific immunity of juvenile yellow catfish (Pelteobagrus fulvidraco)

This study investigated the effects of feeding different concentrations of chitosan on the growth performance, body composition and non-specific immune function of juvenile yellow catfish (Pelteobagrus fulvidraco). Four kinds of experimental diets were respectively prepared by adding 0 (control group), 5, 10 and 15 g/kg of chitosan to the basal feed and fed to juvenile yellow catfish for 8 weeks. Results show that the body weight gain rate, specific growth rate, survival rate, body protein content, serum superoxide dismutase activity, catalase activity, glutathione peroxidise activity, lysozyme activity and disease resistance ability against Aeromonas hydrophila of the experimental group with chitosan added to its diet were significantly higher than those of the control group optimally by 36.22 %, 14.37 %, 9.46 %, 8.97 %, 50.89 %, 33.15 %, 21.52 %, 40.80 %, 41.09 %, and 79.71 %, respectively (P < 0.05). No significant differences in feed efficiency among all groups (P > 0.05) were observed. The optimum dose of dietary chitosan required for the maximum growth of juvenile yellow catfish was 8.95 g/kg. Therefore, adding an appropriate amount of chitosan (8.95 g/kg) to the feed of yellow catfish can significantly improve its growth performance, ameliorate body composition and enhance its non-specific immunity.

Dietary chitosan promotes the growth, biochemical composition, gut microbiota, hematological parameters and internal organ morphology of juvenile Barbonymus gonionotus

In this study, we determined the effects of dietary chitosan on the growth, biochemical composition, gut microbiota, and hematological and histological parameters of juvenile Barbonymus gonionotus. Three test diets containing three different concentrations (1, 2, and 3 g kg-1 feed) of dietary chitosan were formulated. A basal diet without dietary chitosan was considered a control, and the fish were reared for 60 days. Comparing the effects of the dietary chitosan-containing diets with those of the control diet, we found that dietary chitosan significantly improved the muscle growth, nutrient and mineral contents, hematological parameters, lactic acid bacterium abundance, and digestive enzyme activities of B. gonionotus. Moreover, dietary chitosan significantly inhibited the growth of pathogenic bacteria in fish. Interestingly, an increase in the dietary chitosan level significantly enhanced the protein contents of the muscles and inversely significantly decreased the lipid contents compared to those with the basal diet. Quantitative study revealed that dietary chitosan significantly enhanced the length of intestinal villi, and qualitative study showed that dietary chitosan considerably reduced the fat content in the liver and improved the morphology of the kidney compared to those with the basal diet. Taken together, our results suggest that the application of dietary chitosan at a dose of 1 g kg-1 feed produced the highest benefit to treated B. gonionotus, indicating its potential for safe use in aquaculture.

Chitin derivatives of NAG and chitosan nanoparticles from marine disposal yards and their use for economically feasible fish feed development

Globally, the disposal of shellfishery waste is a major challenge and causes a risk to the coastal region. For potential development in aquaculture, the use of safe supplements to improve fish production and health is important. Chitosan (CS) used as feed additives for several fish species that enhanced production and immunity. The present study was intended to assess the effect of feed additives N-acetyl-d-glucosamine (NAG) loaded chitosan nanoparticles (CSNPs) on productivity, survival rate, and protein conversion efficiency of Oreochromis niloticus (L.). This is the first report on the effect of CSNPs and NAG loaded CSNPs as feed additives enhanced growth performance and non-specific immunity of O. niloticus. CSNPs and NAG loaded CSNPs were synthesized and characterized by scanning and transmission electron microscope, FT-IR, X-ray diffraction, particle size distribution, and zeta sizer. Fish (15.30 ± 0.23 g) administered diets fortified with 0.0, 0.25, 0.5, 1.0, and 2.0 g CSNPs/kg feed loaded with NAG for 45 d. The diets containing 1.0 g/kg NAG loaded CSNPs enhanced specific growth rate, weight gain, survival rate, respiratory burst, and lysozyme activities of tilapia compared control group. The data shows biologically active CSNPs and NAG loaded CSNPs are potent antimicrobial agents against selected bacterial pathogens. In conclusion, the findings suggested that the dietary supplement containing NAG loaded CSNPs significantly increased immune-modulatory properties, growth performance, and enhanced their disease resistance of Nile tilapia.

The influence of probiotics of different microbiological composition on histology of the gastrointestinal tract of juvenile Oncorhynchus mykiss

This article presents results of the influence of three probiotic feed additive of various microbiological composition: Bacillus subtilis (VKPM B-2335); B. subtilis (OZ-2 VKPM-11966) + Bacillus amyloliquefaciens (OZ-3 VKPM-11967); Lactobacillus acidophilus (VKPM B-3235) on the growth and histology of the organs of the gastrointestinal tract of juvenile Oncorhynchus mykiss by morphometric parameters. These probiotic bacteria are the most commonly used in aquaculture. The effect of the probiotic feed additive led to the increase in fish growth and influenced different sections of the gastrointestinal tract. The biggest change was found in the mid intestine and the reliable difference compared with the control diet was obtained at the following parameters: lamina propria width, intraepithelial lymphocytes number of prismatic epithelium and goblet cells area. The changes in the pyloric appendages were less obvious but reported as playing an important functional role in digestion. The liver preserved normal functional structure in all series of the experiment except for the group with L. acidophilus, where hepatocyte small-drop vacuolization was observed. That might be connected with the change of the digest activity resulting from a decrease in secretory activity of the intestinal exocrinocytes. The use of all probiotic feed additives led to a similar change in morphometric parameters in all groups, which suggests a decrease in the immune response.

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.

Dietary Chitosan Nanoparticles: Potential Role in Modulation of Rainbow Trout (Oncorhynchus mykiss) Antibacterial Defense and Intestinal Immunity against Enteric Redmouth Disease

Bio-nanotechnology employing bio-sourced nanomaterial is an emerging avenue serving the field of fish medicine. Marine-sourced chitosan nanoparticles (CSNPs) is a well-known antimicrobial and immunomodulatory reagent with low or no harm side effects on fish or their human consumers. In this study, in vitro skin mucus and serum antibacterial activity assays along with intestinal histology, histochemical, and gene expression analyses were performed to evaluate the impact of dietary CSNPs (5 g kg⁻¹ dry feed) on rainbow trout resistance against ‘enteric redmouth’ disease. Two treatment conditions were included; short-term prophylactic-regimen for 21 days before the bacterial challenge, and long-term therapeutic-regimen for 21 days before the challenge and extended for 28 days after the challenge. Our results revealed higher antibacterial defense ability and positive intestinal histochemical and molecular traits of rainbow trout after dietary CSNPs. The prophylactic-regimen improved trout health while the therapeutic regimen improved their disease resistance and lowered their morbidity. Therefore, it is anticipated that CSNPs is an effective antibacterial and immunomodulatory fish feed supplement against the infectious threats. However, the CSNPs seem to be more effective in the therapeutic application rather than being used for short-term prophylactic applications.

Withania somnifera dietary supplementation improves lipid profile, intestinal histomorphology in healthy Nile tilapia (Oreochromis niloticus), and modulates cytokines response to Streptococcus infection

Despite Withania somnifera (WS), stimulating effects have been investigated on many animal species, its role on lipid profile and intestinal histomorphology in healthy animals, and its modulating role on pro-inflammatory cytokines following infection in fish are yet scarce. In this context, lipid profile, liver, and intestinal histomorphology were measured in Nile tilapia fed with a basal diet or diets containing 2.5 and 5% of supplementary WS for 60 days. Besides, cytokines response was measured at 1, 3,7, and 14 days following Streptococcus iniae (S. iniae) infection after the feeding trial. All lipid profile parameters were nominally lowered, excluding high-density lipoprotein (HDL) that exhibited a significant increase in WS 5% group compared to other groups. Improved gut health integrity was observed, especially in WS 5% group in terms of increased goblet cell numbers, villous height, the width of lamina propria in all parts of the intestine, and a decrease in the diameter of the intestinal lumen of the distal intestine only. A significant down-regulation in the mRNA transcript level of cytokine genes (interleukin 1β/IL-1β, tumor necrosis factor α/TNFα, and interleukin 6/IL-6) was demonstrated in the kidney and spleen of WS-supplemented groups following S. iniae infection compared with the control infected (positive control/PC) group. Our findings give new insights for the potential roles of WS dietary inclusion not only on lipid profile and intestinal health integrity improvement in healthy fish under normal rearing but also as a prophylactic against the infection. Thus, WS can be incorporated as a promising nutraceutical in aquaculture.

Effects of Chitosan-Gentamicin Conjugate Supplement on Non-Specific Immunity, Aquaculture Water, Intestinal Histology and Microbiota of Pacific White Shrimp (Litopenaeus vannamei)

When the aquaculture water environment deteriorates or the temperature rises, shrimp are susceptible to viral or bacterial infections, causing a large number of deaths. This study comprehensively evaluated the effects of the oral administration of a chitosan-gentamicin conjugate (CS-GT) after Litopenaeus vannamei were infected with Vibrio parahaemolyticus, through nonspecific immunity parameter detection, intestinal morphology observation, and the assessment of microbial flora diversification by 16S rRNA gene sequencing. The results showed that the oral administration of CS-GT significantly increased total hemocyte counts and reduced hemocyte apoptosis in shrimp (p < 0.05). The parameters (including superoxide dismutase, glutathione peroxidase, glutathione, lysozyme, acid phosphatase, alkaline phosphatase, and phenoloxidase) were significantly increased (p < 0.05). The integrity of the intestinal epithelial cells and basement membrane were enhanced, which correspondingly alleviated intestinal injury. In terms of the microbiome, the abundances of Vibrio (Gram-negative bacteria and food-borne pathogens) in the water and gut were significantly reduced. The canonical correspondence analysis (CCA) showed that the abundances of Vibrio both in the water and gut were negatively correlated with CS-GT dosage. In conclusion, the oral administration of CS-GT can improve the immunity of shrimp against pathogenic bacteria and significantly reduce the relative abundances of Vibrio in aquaculture water and the gut of Litopenaeus vannamei.

Effects of dietary chitosan on growth rate, small intestinal morphology, nutrients apparent utilization and digestive enzyme activities of growing Huoyan geese

Dietary chitosan (CS) supplementation could improve the growth rate, small intestinal morphology, nutrients apparent digestibility and digestive enzyme activities in pigs, broiler chickens, rats and fish, whereas no data has been reported about the effect of CS on the growing Huoyan geese. Therefore, this study was designed to investigate the effects of CS on growth rate, small intestinal morphology, nutrients apparent utilization and digestive enzyme activities of growing Huoyan geese. Three hundred and twenty (28 days of age, gender balance) Huoyan geese were randomly divided into control, CS100, CS200 and CS400 groups (based on BW) with 20 geese per pen and 4 replicates pen per group, and the feeding experiment lasted for 4 weeks. The 4 diets contained 0, 100, 200 and 400 mg CS per kg feed, respectively. The results showed that CS200 groups had higher average daily gain, final BW, apparent utilization of DM and CP, and lower feed/gain ratio compared with the control group (P < 0.05). Meanwhile, CS100 and CS200 groups had higher villus height, villus height/crypt depth ratio and lower crypt depth in duodenum and jejunum than those in the control group (P < 0.05). The geese in CS100 and CS200 groups had higher villus height, villus height/crypt depth ratio and lower crypt depth of ileum compared with those in control and CS400 groups (P < 0.05). In addition, compared with the control group, CS200 group has higher trypsin activities and lower lipase activities in duodenal, jejunal and ileal contents (P < 0.05). The results suggested that addition of 200 mg/kg CS had positive effects on growth rate, small intestinal morphology, nutrients apparent utilization and digestive enzyme activities of growing Huoyan geese.

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.

The growth performance, body composition and nonspecific immunity of Tilapia (Oreochromis niloticus) affected by chitosan

The aim of this study was to investigate the effects of dietary chitosan on the growth performance, body composition and non-specific immunity of tilapia (Oreochromis niloticus). Chitosan were added to the basic diet to formulate five kinds of test feeds (0, 2, 4, 6 and 8 g kg^-1). The diets containing 4 g kg^-1 chitosan increased body weight gain, feed conversion rate, specific growth rate, body protein, superoxide dismutase activity, catalase activity, lysozyme, disease resistance ability against Aeromonas hydrophila and decreased hepatopancrease lipid levels, plasma total cholesterol, plasma triacylglycerol, aspartate aminotransferase and alanine aminotransferase of tilapias compared with those of the control group. However, a high level of chitosan (8 g kg^-1) decreased its efficiency compared to moderate level of chitosan (4 g kg^-1). The results demonstrated that chitosan could promote the growth of tilapias and improve their disease resistance against A. hydrophila.

Effects of different molar mass chitooligosaccharides on growth, antioxidant capacity, non-specific immune response, and resistance to Aeromonas hydrophila in GIFT tilapia Oreochromis niloticus

A feeding trial was conducted to evaluate the effects of different molar mass chitooligosaccharides (1000 Da, 3000 Da and 8000 Da) on growth, antioxidant capacity, non-specific immune response, and resistance to Aeromonas hydrophila in GIFT tilapia (Oreochromis niloticus). A total of 600 fish were divided into four treatments with five replicates of thirty fish per tank. The results showed that the supplementation of 1000 Da and 3000 Da COS significantly improved the growth performance and feed utilization in GIFT tilapia. The trend of decreasing total cholesterol, triglyceride, ALT, and ACP activity was observed in fish fed diet supplemented COS. The supplementation of 1000 Da and 3000 Da COS significantly improved the serum TAC activity, and decreased the serum MDA and catalase activities (P < 0.05). The lysozyme activity of blood, liver, and gills in fish fed diets supplemented with 1000 Da and 3000 Da COS was significantly higher than that of fish fed control diet after 56 days of feeding (P < 0.05). The phagocytic activity and phagocytic index of fish fed diets supplemented with 1000 Da and 3000 Da COS were significantly higher than those of fish fed control diet. Post-challenge test showed that fish mortality in 1000 Da, 3000 Da, and 8000 Da COS groups were significantly lower than that of fish in control group (P < 0.05). In conclusion, the present study indicated that dietary 1000 Da and 3000 Da COS supplementation could enhance more performance and immune response of GIFT tilapia than 8000 Da COS.

Effects of probiotic supplementation of a plant-based protein diet on intestinal microbial diversity, digestive enzyme activity, intestinal structure, and immunity in olive flounder (Paralichthys olivaceus)

The aim of this study was to investigate the effects of intestinal microbial manipulation by dietary probiotic supplementation on digestive enzyme activity, immune-related gene transcription, intestinal structure alteration, and viability against pathogenic challenge in olive flounder. Similar-sized flounders (14.92 ± 0.21 g) were divided into three groups and supplemented with a control (without probiotic) or 1 × 10⁸ CFU/g diet of each of Bacillus sp. SJ-10 (ProB) and Lactobacillus plantarum (ProL) for eight weeks. At the end of the feeding trial, the estimated intestinal microbial richness (Chao1) and diversity (Shannon) demonstrated a significant (P < 0.05) abundance in the ProB group (484.80 ± 88.75, 5.08 ± 0.17) compared to the ProL (285.32 ± 17.78, 4.54 ± 0.09) and control groups (263.23 ± 20.20, 4.30 ± 0.20). A similar alteration phenomenon was also found at the phylum level, with a higher abundance of Proteobacteria, Actinobacteria, and Acidobacteria. Trypsin and lipase activities were elevated in both the ProB and ProL groups compared to the control, but amylase was only higher in the ProB group. The expression levels of pro-inflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 were significantly higher in the ProB group than in the other two groups. There was a significant increase in transcription of IL-10 in both the ProB and ProL groups compared to the control. The length of villi and microvilli of probiotic-fed olive flounder was increased but was not significantly different from the control group. In an in vivo challenge experiment with Streptococcus iniae (1 × 10⁸ CFU/mL), the survival rates of the ProB and ProL groups were 29.17% and 12.50%, respectively, when control mortality reached 100%. Therefore, intestinal microbiota manipulation by probiotic supplementation increased the richness of the bacterial population, digestive enzyme activity, intestinal immune gene transcription, and infectious disease protection in olive flounder.

Effects of chitosan-supplemented diets on the growth performance, nonspecific immunity and health of loach fish (Misgurnus anguillicadatus)

This study investigated the effects of dietary chitosan on the growth performance and nonspecific immunity of loaches (Misgurnus anguillicadatus). Four practical diets at three levels of chitosan (1, 5 and 10 g/kg) were fed to loach (3.13 ± 0.02 g) in triplicate groups (20 fish per replicate) for 10 weeks. Contrary to high-chitosan treatment, the administration of low or moderate levels of oral chitosan (1 or 5 g/kg) significantly increased the body weight gain, specific growth rate and condition factor. The oral administration of chitosan significantly increased the survival rate, phenoloxidase, superoxide dismutase, glutathione peroxidase, lysozyme, acid phosphatase and alkaline phosphatase activities, as well as the immunoglobulin M and complement 3 contents and the disease resistance against Aeromonas hydrophila. The optimum dose of dietary chitosan required for the maximum growth of loach was 5 g/kg. These results indicated that chitosan exerted immunostimulatory effects on loaches (M. anguillicadatus) and can thus be used as a dietary supplement.

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.

Chitooligosaccharide supplementation in low-fish meal diets for Pacific white shrimp (Litopenaeus vannamei): Effects on growth, innate immunity, gut histology, and immune-related genes expression

This study evaluated the effects of supplementing chitooligosaccharide (COS) in low fish meal (FM) diets on growth, immune response, intestine and hepatopancrease histology, and expression of inflammatory and immune-related genes in Pacific white shrimp (Litopenaeus vannamei). A basal diet was formulated using FM and soybean meal (SM) as primary protein sources and considered as a high FM (HFM) diet, then a low FM (LFM) diet was prepared by substituting 50% of FM with SM and supplemented with 0, 0.3, 0.6, 0.9, 1.2 or 1.5 g COS kg-1 diet (LFM, COS3, COS6, COS9, COS12 and COS15 diets). Each diet was fed to quadruplicate groups of shrimp (0.9 g) to apparent satiation three times daily for eight weeks. At the end of the experiment no significant changes in growth and survival rate were observed among treatments (P > 0.05). FM replacement led to significant (P < 0.05) reduction of serum lysozyme activity and significant improvements were obtained by adding 0.3 or 0.6 g kg-1 COS to the LFM diet. A significant decrease in nitric oxide synthase activity was found in LFM group and no beneficial effects could be achieved by COS application. LFM group showed higher hepatopancrease superoxide dismutase and glutathione peroxidase activities than HFM group and further enhancements were obtained by COS application. Hepatopancrease total antioxidant capacity and alkaline phosphatase activity decreased in LFM group and COS supplementation improved their values. Expression of lysozyme, crustin, Pen3 and proPo genes were significantly up-regulated in hepatopancrease of groups received 0.3-0.9 g COS kg-1 diet. FM substitution enhanced the expression of HSP70 and inflammatory genes such as AIF and TNF in hepatopancrease and intestine, and COS administration at a moderate level down-regulated their expression level. Remarkable enhancement in intestinal fold height was obtained by inclusion of 0.3 or 0.6 g COS kg-1 diet compared to the group received LFM diet. Shrimps fed HFM and COS containing diets exhibited higher number of E-cells within their hepatopancrease tubules than the LFM group. The findings in this study clearly demonstrated that COS could enhance non-specific immune response and antioxidant activity, and ameliorate the negative impacts of high SM diets on gut and hepatopancrease health in pacific white shrimp. The optimum inclusion level of COS seems to be 0.3-0.6 g kg-1 of diet.

Effects of dietary raffinose on growth, non-specific immunity, intestinal morphology and microbiome of juvenile hybrid sturgeon (Acipenser baeri Brandt ♀ × A. schrenckii Brandt ♂)

This study was performed to determine the efficacy of raffinose on the growth, non-specific immunity, intestinal morphology and microbiota of juvenile hybrid sturgeon, (Acipenser baeri Brandt ♀ × A. schrenckii Brandt ♂). Hybrid sturgeons were divided into 2 groups and each group was fed with diets supplemented with or without raffinose for 56 days. Hybrid sturgeon fed diet supplemented with raffinose had significantly higher final body weight (FBW), specific growth rate (SGR), and weight gain ratio (WGR) than fish fed the control diet (P < 0.05). Raffinose in diet had no negative effect on feed intake (FI) and feed conversion ratio (FCR) (P > 0.05). Compared with the control diet, the myeloperoxidase (MPO) and respiratory burst (NBT) activitives were significantly higher in sturgeon fed the raffinose supplemented diet (P < 0.05). The increasing of intestinal villi area and mucosal folds were observed in intestinal tract of sturgeon when they fed the raffinose supplemented diet. Meanwhile, the residual bait of intestinal tract was relatively lower in sturgeon with raffinose treatment. High-throughput sequencing revealed that majority of reads derived from the sturgeon digesta were constituted by members of Proteobacteria, Firmicutes, Fusobacteria and Actinobacteria. Shannon's diversity index existed significant difference among dietary treatments indicating that the overall microbial community was modified to a large extent by dietary raffinose. In conclusion, supplementation of the diet with raffinose is capable of improving hybrid sturgeon growth performances and intestinal morphology, modifying the intestinal microbial composition.