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The possibility of replacing fish meal with plant protein sources (soybean meal and corn gluten) for beluga (initial body mass 159.55±2.14g) was studied in autumn 2009. Experimental feeds with 46.5% of crude protein, GE: 5.4 Cal g-1 in four replacement levels: 0, 270, 450 and 660 gr kg1 were prepared and fish were fed on the diets for 60 days. Significant differences were found in growth performance (P<0.05) of different diets. Biomass gain, specific growth rate, feed conversion rate and protein efficiency ratio in fish feed with diet 1 was higher (P<0.05) that the other ones. However, growth performance in diets 2 and 3 were not significantly different (P>0.05). Moisture of beluga carcass fed with diet 4 was significantly higher (P<0.05) that the other diets. However, protein, fat and ash were not significantly different (P>0.05) among diets. The hematocrit percentage was significantly higher in experimental treatments 1 and 2 than 3 and 4 and the plasma glucose was significantly different between diets 1 and 4 (P<0.05). With decreased fish meal, significantly (P<0.05) decreased plasma cholesterol was found in diet 1 compared to the diets 3 and 4. Results showed that combination of soybean meal and corn gluten is not a good substitute for fish meal and deceased growth performance of the fish. *Corresponding author

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The probiotic effects of inactive yeast, Saccharomyces cerevisiae var. ellipsoideus was studied on growth performance, survival and intestinal microbiota of beluga juveniles (Huso huso). The study was done in complete randomize design that included feeding of beluga juveniles with diets supplemented with 0 (control), 1, 2 and 5% yeast (4 treatments with 3 replicates). Beluga juveniles (11.40±0.56g) were randomly allocated in 12 oval tanks at a density of 35 fish per tank and triplicate group were fed with experimental diets. At the end of the trial, growth factors (final weight, weight gain, SGR, CF) as well as feed conversion ratio (FCR), body composition (protein, lipid, ash, moisture) and intestinal microbiota (total viable bacteria and Lactobacillus spp. levels) were determined. Our results confirmed that juveniles fed on diet supplemented with 5% S. cerevisiae var. ellipsoideus had significantly higher final weight, weight gain, specific growth rate (SGR) and lower food conversion ratio compared to control and 1% treatment (P<0.05). However, there were no significant differences between SGR of 5 and 2% yeast treatments (P>0.05). The study of body composition showed no significant difference between treatments (P>0.05). Total viable bacteria and Lactobacillus spp. count were significantly higher in 5% treatment compared to control (P<0.05). However, there was no significant difference between Lactobacillus spp. levels in 5 and 2% treatments (P>0.05).

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The aim of the present study was to investigate the effects of dietary oligofructose (1, 2 and 3%) on blood profiles of beluga Huso huso juveniles (18.77±0.76g). After 7 weeks feeding on experimental diets hematological parameters, metabolic products (cholesterol, glucose and total protein) and serum enzymes (lactate dehydrogenase, alkaline phosphatase, alanine aminotransferase and aspartate aminotransferase) were measured. Compared to the control group (0% oligfructose), oligofructose had no effects on red blood cell counts (RBC), mean corposcular volume (MCV), mean cellular hemoglobin concentration (MCH) or mean cell hemoglobin concentration (MCHC) (P>0.05). However, hematocrit (Hct), hemoglobin concentration (Hb) and leucocyte counts (WBC) were significantly higher in fish fed 2% oligofructose (P<0.05). Although serum glucose and total protein remained unaffected, cholesterol was significantly lower in the 2% oligofructose group (P<0.05). Our results showed oligofructose had no significant effects on serum lactate dehydrogenase, alkaline phosphatase, alanine aminotransferase and aspartate aminotransferase (P>0.05). These results indicate an immunomodulatory effect and the potential to reduce serum cholesterol levels in beluga sturgeon. *Corresponding author

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High mortality of beluga prelarvae (Huso huso) occurs in hatcheries and this appears to be linked to various abnormalities. Hence, this study was conducted to compare the body shape of alive and dead beluga prelarvae (5DPH) and to find the patterns of deformities among losses using geometric morphometric method. This method was applied to extract shape data as landmark’s Cartesian coordinates. Specimens were photographed using digital camera and the landmarks put on two-dimensional images using tpsDig2. Landmark data after GPA (Generalized Procrustes Analysis) analyzed using PCA and DFA. Results showed significant differences between alive and dead prelarvae shapes. In addition, various pattern of deformities found in the operculum, yolk sac and caudal peduncle parts. Future studies are suggested on larvae and juvenile stage.

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The effects of dietary selenium (Se) were investigated on the oxidative stress of beluga, Huso huso, fed high dietary copper (Cu). The basal diet with high Cu (50mg Cu/kg) was supplemented with low (0mg Se/kg, HCuLSe), adequate (11mg Se/kg, HCuNSe) and 5× adequate (55mg Se/kg, HCuHSe) of Seandfed to fish with initial body mean (±SD) weight 14.96 ± 1.39g for 12 weeks. Basal diets containing adequate Se (11mg Se/kg) and adequate Cu (10mg Cu/kg) were used as controls (NCuNSe). Weight gain, specific growth rate and condition factor for fish fed the HCuHSe diet was significantly lower than fish that fed the other diets. Se and Cu content was positively correlated with dietary Se and Cu concentrations. Hepatic Se concentration was higher in fish fed the HCuHSe diet than fish that fed other diets. Thiobarbituric acid-reactive substances (TBARS) were significantly lower. Whereas, Glutathione peroxidase activity activities were significantly higher in liver tissue of fish fed HCuHSediet than those fish fed other diets. Plasma total immunoglobulin concentration and lysozyme activity were higherin fish fed the NCuNSe diet, followed by fish fed the HCuNSe diet, and were lower in fish fed the HCuHSe diet. The results indicated that optimum levels of Cu and Se ingestion induced an oxidative stress in beluga and improved their immune response. High dietary Se (5×adequate) supplementation reduced the oxidative stress and depressed the immune response of the fish. *Corresponding author

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A 2 × 4 factorial design was conducted to study the effects of dietary protein and energy levels on growth performance of juvenile beluga (Huso huso) with average weight of 49.85 ± 1.64 g. Experiments were conducted with two dietary protein levels (40 and 45%) and four dietary energy level (18.5, 19.8, 21.1 and 22.4 MJ/kg diet) by ratio P/E (18.03 to 24.14 mg/kj). Fish were fed the experimental diets for 110 days. In each of the protein levels (40 and 45%), the feed efficiency, body weight increase, Protein efficiency ratio, specific growth rate, final body weight and total feed intake of fish improved significantly as dietary energy levels increased (P≤ 0.05). Growth of fish fed high- energy diets was significantly higher than those of fish fed low- energy diets at 40 and 45% dietary protein levels (P≤ 0.05). Protein content of carcass increased when dietary protein increased, but there was no significant different (P≥ 0.05) between 40 and 45 % protein. Lipid content of fish fed diet high- energy level was significantly higher than those of fish fed low dietary energy (P≤ 0.05). So the maximum growth and weight( 22.4 ± 5.3 gr) was observed in treatment, that were fed diets containing 45% protein & 22.4 mega joule crude energy. Considering that no significant difference were affected for among the diet for the parameters studied, the diet containing 40 % protein, 21 % fat and 21.1 mega Joule crude energy per kilogram diet with a P/E ratio of 20 mg protein per kilo joule from a good quality source is a suitable diet in terms of physiology and economy can be considered a suitable diet to produce maximum growth in juvenile beluga in the weight class 49 to 200g.

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A feeding trial was conducted to examine the effects of dietary supplementation of lysine and methionine on growth, nutrient utilization and carcass compositions in beluga, Huso huso.  Four experimental soy protein based diets D₀ (without lysine or methionine supplementation), D₁ (lysine supplementation alone), D₂ (methionine supplementation alone) and D₃ (both lysine and methionine supplementation) were fed to triplicate groups. 240 fish with average weight of 144.6 ± 4.64 g were fed the experimental diets for 12wk. L-Lysine and DL-methionine were added to the diets containing 344 g kg^-1 soybean meals at 22.02 and 12.94 g kg^-1 of dry diet respectively. Significant higher weight gain, specific growth rate, protein efficiency ratio, condition factor, feed efficiency ratio, whole muscle protein and protein apparent digestibility were observed in fish fed soya protein-based diet supplemented with both lysine and methionine than that of fish of other dietary groups. There were no significant differences among fish fed diet supplemented with either methionine or lysine. Growth performances, feed utilization, carcass composition and apparent digestibility coefficients of protein, lipid and dry matter of fish fed control diet was significantly lower than those of fish fed diet supplemented both lysine and methionine and supplemented with either methionine or lysine. It can be concluded that beluga, fingerlings effectively utilize the supplemental amino acids (L-Lysine at 22.02 g kg^-1 dry diet and DL-methionine at 12.94 g kg^-1 dry diet) in the diets containing 344 g kg^-1 soybean meals for better carcass proximate compositions, growth performance and feed efficiency and utilization.

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Allometric growth pattern is a phenomena during early development of fishes. This research was conducted to study the allometric growth patterns of a hybrid triploid sturgeon (Acipenser baeri♂ x Huso huso♀) during early developmental stage up to 50 day post hatching (dph). Morphometric parameters of this study obtained from 2D pictures of specimens using the software ImageJ and allometric growth pattern was calculated as a power function of total length using non-transformed data: Y=ax^b. The results revealed that during early development of the triploid sturgeon after hatching, head and tail regions have positive allometric growth pattern that can be as result of importance vital functions, including swimming, respiration and sensory systems during this period. The inflexion points of the most body parts have been occurred prior 25dph and afterward their growth patterns were isometric. Despite the genetic difference between the hybrid triploid sturgeon with its parents, the results showed that its allometric growth patterns have many similarities with them. This results, also, provide evidence that the phenotypic plasticity plays important role in regulation of the body shape during early development.
 

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This study was performed in order to evaluate the effects of chronic stress (density) and acute stress (handling) existed in culture environments on stress and hematological parameters of beluga sturgeon (Huso huso) under winter condition (below 10°C) after application of anesthesia. Fish with mean (± SE) weight of 399 ± 1.4 g were kept in the low (1 kg/m²) and high densities (8 kg/m²) in three replicates for a week. Then, fish were held under stress condition so that they were quickly removed from the rearing tank and then anesthetized for 2 minutes in container (50 l) includes 400 mg/l clove powder extract. They were then returned to the original tanks. Blood samples were taken before the stress (0 time), 1, 3, 6, 12, 24 and 48 hours after application of the stress;and the  stress indicators (cortisol, glucose and lactate) and hematological parameters (hematocrit, hemoglobin, number of red blood cells, MCV, MCH, MCHC, number of white blood cells, lymphocytes, neutrophils, eosinophils and monocytes) were measured. No differences in measured parameters were observed after one week of holding fish at low and high densities. The results of stress indicators, one hour after acute stress and anesthesia showed a significant difference with resting time (p<0.001). Also significant difference was observed on lactate levels between the low density and high density densities at 3 h after acute stress and anesthesia (p=0.032). Number of white blood cells at 1 and 6 h after acute stress and anesthesia in high density showed significant difference with resting time (p<0.001). MCV showed significant difference between two treatments at 48 h after the stress and anesthesia (p=0.016). The other parameters did not show any significant difference between treatments (p>0.05). The results revealed that beluga sturgeon has high resistance against chronic and acute stressors and anesthesia. However, it seems that anesthesia could not control the low negative effects of stress even in this condition of low temperature.
 
 
 
 

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Proximate, fatty acid compositions and nutritional quality indices of lipids between the caviar of wild and farmed Caspian Sea Beluga (Huso huso) sturgeon and their cardiovascular effects have been compared. Protein, lipid, moisture and ash were analyzed by using standard methods of proximate composition analysis and fatty acids profile determined by gas chromatography method. The fatty acid composition varied in both wild and farmed Beluga caviars, but they did no differ in proximate compositions. The most notable difference (p<0.05) was the higher concentration of linoleic acid (C18:2n6) in farmed Beluga caviar (8.32%) than wild ones (0.37%). The total ω-3 in wild caviar (38.42%) had no significant difference from farmed ones (30.42%) (p>0.05), but the content of total ω-6 was significantly higher in farmed (17.39%) samples than wild ones (13.27%). The ratio of ω-3 /ω-6 was higher in wild sample (2.9) from farmed ones (1.75) (p<0.05). Between wild and farmed caviars respectively, the atherogenic, (0.29, 0.28), thrombogenic (0.18, 0.21), Hypocholesterolaemic/Hypercholesterolaemic (2.45, 2.52) Polyene (1.73, 1.46) and Peroxidisability (326.86, 269.03) indexes contents had no significant differences (p>0.05). The present study indicated that the caviar from farmed Beluga like wild ones could be considered as a good food sources, besides, it has good balanced with lipid nutritional quality indices to cardiovascular prevents and finally it has important impact on protecting wild population from elimination.

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The aim of this study was to identify and compare the mineral micronutrients compositions, color and genetic structure differences between the wild and farmed Caspian Sea Beluga (Huso huso) sturgeon caviar, which plays an important role to caviar market transparency to prove farmed caviar quality and nutritional values and wild and farmed Beluga caviar genetic identification. Mineral micronutrients were measured by atomic absorption, spectrophotometric and flame atomic emission spectroscopy methods, color by colorimeter and genetic differences by PCR sequencing method. Results showed that, wild samples contained higher amounts of calcium, magnesium, phosphorus and potassium than farmed ones (P<0.05), while, iron, copper and zinc were higher in farmed samples (P<0.05). Sodium content had no significant differences between wild and farmed samples, 4239.43±2.72 and 4237.21±2.18 (µg/g wet weight) respectively (P>0.05). L value in wild sample was 28.29 and in farmed one was 46%, a value was 1.34 and 2.66% and b value was 10.72 and 16.27% respectively (P<0.05), ΔE (color differences) was 15.21 between two samples. Genetic structure had no significant differences between two samples. In conclusion, it can be said that, there was significant differences in mineral micronutrients contents and color but genetic structure did not show any significant differences between two samples.
 

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In the present study, the effect of Pullulan coating with watercress extract on the quality and shelf life of fresh beluga sturgeon fillet stored in a refrigerator over a period of 16 days was investigated. First, the watercress extract was extracted by ultrasound and soxhlet (solvent) method and the amount of phenolic compounds and antioxidant activity of the extract (DPPH free radical activity test) were determined. The values of phenolic compounds for soxhlet extract were equal to 586.53 mg gallic acid per gram of dry weight and for ultrasonic extract was 879.57 mg/g dry weight and the antioxidant properties of watercress extracted by ultrasound were significantly higher than soxhlet method (p<0.05), so ultrasound extracts were added to the pullulan coating. Then, 4 treatments were included: control, pullulan coating, pullulan coating + watercress extract 500 ppm, pullulan coating + watercress extract 1000 ppm were analyzed by biochemical parameters such as peroxide value (PV), thiobarbithic acid (TBA), free fatty acid (FFA), total volatile base nitrogen (TVB-N) and pH). The results showed, natural preservation delayed chemical spoilage in compared with control treatment (p<0.05). According to the results pullulan coating + watercress extract 1000 ppm significantly retarded lipid oxidation by decreasing peroxide value and thiobarbituric acid production in the samples and it had the lowest total volatile basic nitrogen and pH (p<0.05). The control treatment had only the allowed chemical range for up to 6 days, but the treatment containing pullulan coating + 1000 ppm extract had the allowed values until the end of the storage period. The final conclusion showed that the coating of pullulan with watercress extract could act as a natural antioxidant, delaying chemical degradation and prolonging the shelf-life of fish fillets.

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Introduction
Fishmeal price were increasing every year and predicted that fish diet will have a wider range of ingredients replaced by fishmeal, such as vegetable sources, microbial protein sources, waste from fishing and animal protein waste (Glencross et al., 2007). Vegetable proteins can replace fish meal to some extent and have a negative effect on the growth of aquatic animals at high levels. But many studies have shown that a mixture of vegetable proteins can improve the amino acid profile compared to single protein source replaced by fish meal (Amaya et al., 2007).  By this method, high replacement with a blend of protein Vegetables have been reported in aquatic animal (Hansen et al., 2007), but increasing fiber, increasing carbohydrates and inappropriate amino acids in diets based on animal and vegetable proteins can led to a negative effect on fish digestive system that showed by growth reduction, immune system depress , low quality meat and even fish fatality in a long-term feeding period (Raskovic et al., 2011). therefore, in this experiment, the effect of a mixture of animal and vegetable proteins replaced by fish meal (levels of 20, 40, 60 and 80%) on the growth indices and digestive system tissue Huso huso were studied.
Methodology
In order to reduce the share of fishmeal in the diet of beluga, a basal diet based on 54% of fishmeal was made. A mixture of animal and vegetable proteins (corn gluten: 35%, wheat gluten: 19.34%, processed soybean flour: 3%, chicken by-products: 20%, meat and bone meal: 8%, blood meal: 3.4%) at 20, 40, 60 and 80% levels replaced with fishmeal (FM) (CGM₂₀, CGM₄₀, CGM₆₀, and CGM₈₀, respectively) and finally 5 isonitrogenous (44% crude protein) and isoenergetic (18 MJ/kg) diets were produced. The fish (Average weight: 167±6.5 gr) were fed to saturation for 12 weeks.  Biometry were carried out on month interval and by carrying out information obtained from fish length, weight and food consumption, growth indices and feed efficiency ratio were calculated. At the end of the feeding period, 30% of the fish population was collected from each tank for histological studies. Three parts of the intestine (hindgut, midgut, and foregut) were removed. It was fixed and stained. Histological studies were carried out by an optical microscope equipped with a monitor.
Results
There was no significant difference in the final weight and length of fish of different treatments (P>0.05). condition factor and percentage of weight gain of fish fed with FM, CGM₂₀, CGM₄₀, CGM₆₀ and CGM₈₀ had no no significant difference and percentage of weight gain was close to each other (243 to 298%) (P>0.05). No significant difference was observed in specific growth rate and daily growth rate and food conversion ratio in fish fed with all diets (P>0.05). Fish fed FM had the highest protein efficiency ratio (1.75±0.23), but protein efficiency ratio in fish fed with CGM₂₀, CGM₄₀, CGM₆₀ and CGM₈₀ was in the range of 1.53 to 1.73%. But no significant difference was observed (P>0.05). Histological studies were carried out by an optical microscope equipped with a monitor. The intestinal tissue of fish fed with CGM80 diet had necrosis and biliary stagnation. However, histological studies in fish fed with FM, CGM₂₀, CGM₄₀, and CGM₆₀ diets showed that the lamina propria space is adequate, the necrosis of enterocytes is negligible, and the number of goblet cells in the anterior, middle, and distal intestine is balanced. The final results confirmed that the CGM₈₀ did not a negative effect on the growth fish, but it caused damage to the digestive system.  In the present study, there is no significant difference in growth indices and food conversion ratio of fish fed with diets based on fish meal and diets based on corn gluten flour (a mixture of corn gluten: 35%, wheat gluten: 19.34%, soybean meal processed: 3%, poultry by product: 20%, meat and bone meal: 8%, blood powder: 4.3%). In this order, it seems be that alternative diets formulation based on a mixture of Animal and vegetable protein sources  were led to enriching of profile and biochemical composition of diet, In addition beluga Compared to white and Siberian sturheon is a species that can be fed with high carbohydrates percentages without growth reduction (Mohseni et al., 2011). In the present experiment, by increasing mixtures based on corn gluten-based in fish diet,  goblet cells were increased and reached to highest value in CGM₈₀. goblet cells are related to immune system and mucus secretion in order to fluidity of digestive tract and create a protective barrier against mechanical and chemical damage (Marchetti et al., 2006). it seems that the increase of goblet cells in beluga fed with a mixture of vegetable proteins (CGM₆₀ and CGM₈₀) is a reaction against to mucous layer necrosis and reduction of intestinal villi in order to further damage of folds by secreting more mucins (Li et al., 2007), but in general, digestive tract epithelium damage in fish fed CGM₂₀, CGM₄₀ diets and CGM₆₀ was negligible compared to fish fed with FM diets and did not lead to enteritis (intestinal inflammation). Therefore, it is suggested to replace fishmeal with a mixture of animal and vegetable proteins at 20 and 40% in Huso huso diet during the fattening stage.
Conflict of Interest
There is no conflict of interest between authors
Acknowledgment
This article is taken from the project " fish meal replacement by vegetable and animal proteins in Huso huso diet " ordered by the governorate of Gilan province. The authors sincerely thank to Mr. Hamid Nasahi, Vice President of Planning, Program and Budget Organization of Gilan Province and Dr. Mohammad Ali Yazdani Sadati for providing financial and hardware for project. They also express their special gratitude to Mr. Hoshang Yeganeh, Mr. Arash Shahbazi and Mr. Mohsen Hoshiar, who were distribution in feeding and rearing of fish.

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Introduction
Aquaculture is increasingly vital for meeting the protein needs of a growing global population. Successful production relies on efficient feed, which accounts for 60% of costs, and the development of high-quality products. Disease management in aquaculture is challenging due to factors like poor nutrition and environmental conditions, making prevention more critical than treatment (Ndashe et al., 2023). Current strategies focus on using immune stimulants and additives, such as organic acids, probiotics, and prebiotics, to enhance fish health and resilience against diseases (Dawood et al., 2018). The use of natural growth stimulants like chitin, chitosan, and lactoferrin has surged due to their economic benefits and minimal environmental impact. These substances not only improve immune responses but also enhance the antibacterial activity of phagocytic cells, contributing to sustainable aquaculture practices. Overall, the shift towards these natural alternatives reflects a growing recognition of their value in promoting fish health and reducing reliance on chemical treatments. Chitosan is a biodegradable and biocompatible polysaccharide derived from glucosamine through the deacetylation of chitin, predominantly found in the exoskeletons of crustaceans, particularly shrimp shells. It offers numerous benefits in aquaculture, notably enhancing fish health and growth. Chitosan stimulates the immune system by increasing levels of immunoglobulin M (IgM) and lysozyme activity, which improves disease resistance. It also boosts antioxidant capacity by enhancing the activity of enzymes like superoxide dismutase (SOD) and catalase (CAT), thereby reducing oxidative stress. Additionally, chitosan promotes gut health by increasing intestinal villi length and digestive enzyme activity, facilitating better nutrient absorption (Mukarram et al., 2023; Zhang et al., 2024). Moreover, chitosan can chelate heavy metals such as cadmium, mitigating their toxic effects on fish, and its antibacterial properties help maintain gut microbiota balance by preventing pathogenic bacteria while promoting beneficial ones. Overall, dietary chitosan supplementation has been shown to enhance growth, health, and stress resistance in various fish species, making it a valuable additive in aquaculture. In the context of sturgeon (Huso huso) farming in Iran, reducing juvenile fish mortality and increasing growth rates are critical for economic efficiency, highlighting the importance of suitable diets and micronutrient balance to enhance immune function and production efficiency.
Methodology
The extraction of chitosan from shrimp shells was carried out through four stages: demineralization, deproteinization, decolorization, and deacetylation. 1260 fish (2.87 ± 0.07 g) after passing the acclimatization period, were fed in 18 tanks with six experimental diets, including control diet (without chitosan, T1), 0.15% (T2), 0.3% (T3), 0.45% (T4), 0.6% (T5) and 0.75% (T6) of chitosan (n=3) for 12 weeks. Then all growth indices such as final weight, growth rate, Protein Efficiency Ratio, and FCR, immunological parameters like lysozyme, ACH50, total immunoglobulin, and IgM were measured. The body composition also was measured after 12 weeks.
Results
The final body weight and body weight gain in treatments containing 0.45%, 0.6%, and 0.75% chitosan were significantly higher compared to the control, 0.15% and 0.3% chitosan treatments. The specific growth rate significantly increased with the higher levels of chitosan, and no significant difference was observed in the group fed with 0.15% chitosan compared to the control group. The hepatosomatic index significantly improved in all chitosan-fed treatments compared to the control group (P≤0.05). The feed conversion ratio significantly improved with increasing levels of chitosan compared to the control group. The protein efficiency ratio also increased in the treatments fed with 0.45%, 0.6%, and 0.75% chitosan compared to the control group, but no significant differences were found in the treatments fed with concentrations of 0.15% and 0.3% chitosan (P≥0.05). The lowest carcass protein level was observed in the control treatment, which showed a statistically significant difference compared to the carcass protein levels of other treatments, except for the 0.15% chitosan treatment (P ≤ 0.05). The carcass protein levels in the 0.45%, 0.6%, and 0.75% chitosan treatments were the highest, but no significant differences were observed among them. The carcass fat level in the 0.45%, 0.6%, and 0.75% chitosan treatments was significantly lower compared to the control group (P≤0.05). With the increase in chitosan concentration in the diets, the serum lysozyme levels significantly increased except for the group consuming 0.15% chitosan (P≤0.05). The results obtained from the complement activity (ACH50) measurements showed that with the increase in chitosan levels in the diet, this indicator significantly increased in the serum (P≤0.05). The total serum immunoglobulin and IgM levels, also increased significantly compared to the control group (P≤0.05).
Discussion and conclusion
Chitosan, has gained attention in aquaculture for its potential as a growth promoter and immunostimulant. Research indicates that dietary chitosan enhances growth performance, feed efficiency, and immune responses in various fish species, including Nile tilapia, common carp, and golden pompano. Optimal chitosan levels, typically ranging from 0.5% to 2%, have been shown to improve weight gain, feed conversion ratios, and overall health status by promoting gut health and enhancing digestive enzyme activities. Studies also highlight chitosan's role in modulating serum biochemical parameters, reducing fat accumulation in the liver, and improving intestinal morphology. The balance of chitosan dosage is crucial, as it can enhance beneficial bacteria while inhibiting harmful ones, thereby supporting the fish's immune system. Overall, chitosan represents a promising, eco-friendly alternative to antibiotics in aquaculture, contributing to sustainable fish farming practices while improving the health and productivity of cultured species. Chitosan also enhances nonspecific immunity and reduces mortality in fish, as evidenced by studies on common carp (Maqsood et al., 2010). However, its effects on feed consumption and conversion ratios can vary, with some studies showing no significant impact on these parameters despite improvements in liver health (Stanek et al., 2023). Overall, chitosan's role in aquaculture highlights its potential as a dietary supplement to improve fish health, growth, and resistance to environmental stressors. Serum parameter measurements are crucial for assessing the metabolic and physiological health of fish, particularly in aquaculture where they are susceptible to opportunistic bacterial infections. Lysozyme activity, an indicator of immune health, was found to increase with dietary chitosan levels. Research indicates that chitosan enhances lysozyme activity across various fish species, including loach, cobia, silver carp, vannamei shrimp, and rainbow trout. Additionally, chitosan supplementation in diets for beluga sturgeon and hybrid sturgeon also boosted lysozyme levels. Chitosan's immune-boosting effects are attributed to its ability to scavenge free radicals, enhancing innate immunity. Complement activity, vital for non-specific immune responses, also increased in fish like Nile tilapia and mrigal when fed chitosan. However, responses to chitosan vary by species and concentration, with some studies indicating potential negative effects at higher doses. Furthermore, IgM levels, a key immunoglobulin in fish, significantly increased with chitosan supplementation, reinforcing its role in adaptive immunity. Overall, optimal chitosan levels in fish diets can significantly enhance immune responses and health. The increase in IgM levels with dietary chitosan is not fully understood, necessitating further research to clarify the mechanisms involved (Salam et al., 2024). Studies indicate that chitosan enhances IgM and total protein levels in fish, such as rainbow trout and golden pompano, although excessive chitosan (10 g/kg) can reduce these benefits (Yu et al., 2023). In tilapia, IgM levels increased significantly up to 1.5% chitosan but decreased at 2% (Zhang et al., 2024). Additionally, recombinant chitosan nanoparticles show promise as alternatives to antibiotics in aquaculture, potentially enhancing disease resistance. This research supports using chitosan in beluga fry diets to improve growth and immune performance while reducing antibiotic reliance, particularly at levels of 0.45% to 0.6%, which positively affected growth, body composition, and immune parameters.
Conflict of Interest
The authors declare that they have no conflict of interest.
Acknowledgment
The authors wish to convey their heartfelt appreciation to all colleagues who supported and facilitated the experiment's necessary infrastructure.