Juvenile Siberian Sturgeon Research Articles

Exploring a novel toxicological mechanism: Ammonia-N induces neurotoxicity, oxidative damage in brain tissue, and modulates the expression of central appetite factors to suppress feeding in juvenile Siberian sturgeon (Acipenser baerii Brandt)

Ammonia-N is a common toxic factor in aquatic environment, known to inhibit fish feeding, yet its mechanism remains unclear. To investigate the toxicological mechanism of ammonia-N in inhibiting fish feeding, this study conducted experiments exposing juvenile Siberian sturgeon (Acipenser baerii) to ammonia-N at concentrations of 0, 5, 10, and 15 mg/L for 14 days. The results revealed a significant reduction in both daily and cumulative food intake. Obviously decreased condition factor (CF), hepatosomatic index (HSI), and viscerosomatic index (VSI) at 15 mg/L (P < 0.05). Besides, the serum ammonia concentration significantly increased on the 14th day, while the neurotoxic marker acetylcholinesterase (AchE) showed a consistent increase over the 14-day period (P < 0.05). Pathological examination of brain tissue demonstrated that ammonia-N induced damage, particularly evident in 15 mg/L ammonia-N group, where severe nerve fiber dissolution was observed. Moreover, the activity of superoxide dismutase (SOD) was significantly increased in the brain on the 1st, 3rd, and 7th day (P < 0.05). RNA-seq analysis o revealed 1566, 2188, and 2026 differentially expressed genes (DEGs) were obtained in the 5, 10, and 15 mg/L ammonia-N groups, respectively, compared to the control group, and 30 DEGs related to appetite regulation were identified. Further quantitative real-time PCR (qPCR) analysis indicated that ammonia-N exposure changed the expressions of appetite factors, including downregulation of agouti-related protein (agrp) and neuropeptide Y (npy), and upregulation of pro-opiomelanocortin (pomc), cocaine-and amphetamine-regulated transcript peptide (cart), and corticotropin releasing factor (crf) (P < 0.05). Therefore, these results suggest that ammonia-N inhibits feeding via neurotoxicity induced oxidative damage which primarily by downregulating appetite promoting factors and upregulating appetite-inhibiting factors. This study lays the groundwork for deeper understanding of the toxicological mechanism of ammonia-N on aquatic animals, particularly its detrimental effects on fish brain function and feeding behavior.

Application of feed enriched with humic additive from peat and dry garlic powder when growing juvenile Siberian sturgeon on an industrial line of cage aquaculture

Cage aquaculture, used in modern industrial sturgeon farming, differ from recirculating water supply systems (RAS) by more natural habitat conditions of fish growing, which are optimal for broodstocks development and maintaining and producing fish seeding material and is more economical. The dominant species for sturgeon aquaculture in Russia and throughout the world is Siberian sturgeon, Acipenser baerii Brandt, 1869, adapted to extreme temperature conditions. When this fish was grown at industrial cage aquaculture enterprises in the European North of Russia under natural conditions, the survival rate of the objects was 99%; growth rates exceeded those of sterlet, Russian sturgeon and F1 hybrids of Russian and Siberian sturgeon; the feed ratio was better compared to fish kept in cages in the Southern Federal District. Seven-year-old sturgeons reared in cages under such conditions had a maximum live weight of more than 8 kg, their physiological parameters were better than those of objects kept in a RAS; indices of reproductive system corresponded to the normal values. To increase the efficiency of keeping Siberian sturgeon in cage aquaculture in the extreme conditions of the Northern regions, feed enriched with multifunctional biologically active compounds of natural origin is used. In this production experiment, the basic forage included the feed additive Humiton of peat humic compounds origin at a dose of 25 ml/kg and/or dried garlic powder at a dose of 30 g/kg; both components previously have shown effectiveness in growing juvenile Siberian sturgeon under RAS conditions. In the experiment, all additives showed activity in all assessed indicators, but the greatest effect was observed when using garlic powder or its combination with Humiton additive. The effectiveness of additives is due to adaptogenic and immunomodulatory effects, the ability to favorably influence the function of the digestive system and improve the absorption of feed nutrients.

The feasibility of using white lupin meal in the feed of juvenile Siberian sturgeon (Acipenser baerii)

Abstract As with other fishes farming, sturgeon farming depends on the use of well-balanced feed to maintain production. Commercial feeds available on the market are often based on soy protein, which, unfortunately, has many adverse effects on these fish. Therefore, alternative constituents are being sought that could be used in sturgeon fish farming. This study was designed to assess the feasibility of using diets containing white lupin meal at levels of 5% and 10% for juvenile Siberian sturgeon, compared to a formulated control group without lupin inclusion and a reference group fed commercial feed. Histological and immunohistochemical analyses were performed, combined with digestive enzyme activity assays. This study showed that feeding with white lupin meal did not adversely affect the rearing parameters, histology, or enzyme metabolism of sturgeons. An increase in the length of intestinal folds in the anterior intestine was observed in the group with 10% lupin meal inclusion, while this trend was not present in the spiral intestine, which may be indicative of a compensatory physiological mechanism when fish are fed less digestible feed. Antioxidative mechanism impairment was also noted in the two experimental groups. However, further research is still required to determine the possibility of using white lupin meal in the feeding of sturgeon fish, especially for more mature specimens.

Supplementation of juvenile Siberian sturgeon (Acipenser baerii) diet with different levels of selenium: Growth performance, digestive enzyme activities, and intestinal histomorphology

This study aimed to investigate the impact of dietary Selenium (Se) on the growth performance, body composition, digestive enzymes, and intestinal histomorphology of Siberian sturgeon, Acipenser baerii. Fish (10.0±0.5 g) were randomly assigned to fifteen 1000-L tanks (30 fish per replicate) in a flow-through system and fed three times a day (08.00, 13.00, 18.00) with isonitrogenous (54.21 % crude protein) and isolipidic (15.63 % crude lipid) diets supplemented with selenomethionine at levels of 0, 0.2, 0.4, 0.8, and 1.6 mg kg−1 providing the analyzed Se of 0.10, 0.29, 0.49, 0.88, and 1.70 mg kg−1, respectively. Each three tanks were allocated to each treatment. After the eight-week feeding trial, weight gain ratio, specific growth rate, and survival rate of fish significantly increased with increasing dietary Se supplementation (p<0.05) and reached to the highest values of 156.00±0.68 %, 1.68±0.07 % d−1, and 98.33±1.66 %, respectively, while the feed conversion ratio declined to the lowest value of 1.79±0.10. Protein and lipid content increased with Se levels to the highest values of 20.15±0.11 % and 8.23±0.05%, respectively (p<0.05). Activity of all digestive enzymes including trypsin, chymotrypsin, α-amylase, lipase, and alkaline phosphatase significantly enhanced with increasing dietary Se levels (p<0.05). Increasing trends in villus height, villus width, muscle thickness, and crypt depth were found by increasing dietary Se supplementation with the highest values of 502.33±31.25, 134.39±13.12, 194.18±11.37, and 67.29±0.12 µm, respectively, in fish fed diet supplemented with 1.70 mg kg−1 Se (p<0.05). Findings of the present study illustrated the beneficial effects of dietary Se on performance, digestive enzymes, and intestinal histomorphology of Siberian sturgeon. According to the polynomial regression analysis, the optimum dietary requirement of Siberian sturgeon was in the range of 1.47–1.69 g kg−1.

Preliminary rearing outcomes of Siberian sturgeon, Acipenser baerii Brandt, juveniles in autonomous hatching and rearing modules

Abstract This study analyzed the rearing indicators of Siberian sturgeon (Acipenser baerii) juveniles reared in tanks of different shapes and at various stocking densities. Rearing was conducted in autonomous hatching and rearing modules. Fish of an average body weight of 47.3±1.0 g were divided into four experimental groups: CL, RL, CH, and RH, which differed in stocking density (20 specimens and 50 specimens) and tank shape (C – circular, R – rectangular). The experiment ran for 28 days. Two-factor analysis indicated that lower stocking density significantly affected the final body weight of juvenile Siberian sturgeon, while tank shape had no effect on growth. The results of the current study on rearing Siberian sturgeon juveniles indicated that tanks of different shapes can be applied, but faster growth was obtained at a lower stocking density.

The effects of diets containing rapeseed meal on Siberian sturgeon (Acipenser baerii) growth, muscle composition, and physiological performance

Sturgeon farming is a rapidly developing aquaculture sector which requires high-quality feeds. As an ingredient of animal feeds, fishmeal is often replaced with cheaper plant-based protein sources, such as rapeseed cake meal, a by-product of canola oil pressing. The aim of the present study is to evaluate the effects of diets containing various levels of rapeseed cake meal on the juvenile Siberian sturgeon (Acipenser baerii) growth, hematological and biochemical parameters, as well as muscle composition. An 8-week feeding trial was conducted on fish with average body weight of 216.2 ± 45.7 g. Fish were fed diets were 0%, 10%, 20%, and 30% of fish meal and soybean meal were replaced with rapeseed meal (groups A, B, C, and D, respectively). Additionally in E diet (30% rapeseed meal) effects of phytase addition RENOZYME® HiPhos 20000 in concentration 2000 IU was tested. During the experiment, no mortalities were observed in each of the studied groups. Similar values of morphometric and breeding parameters were observed in groups A, B, C, D and E. No hematological effects of rapeseed diets occurred, except for significantly lower erythroblast levels in groups B, C, D, and E compared to A. Group B showed a higher plasma glucose concentration compared to the other groups. ALT activity in groups D and E were lower than in groups A, B, and C. The muscles of individuals from group B showed the highest dry matter and fat content, while the highest protein content occurred in group C. Despite significant differences in the values of some parameters, the obtained results indicate that the replacement of 10–30% of fishmeal with rapeseed meal in the feed for the juvenile Siberian sturgeon did not compromise fish survivability, growth performance, health, or body composition, although phytase addition did not improve the effects of administering rapeseed-containing feed.

Repeated intraperitoneal injection of ovine growth hormone accelerates growth in sub-yearling Siberian sturgeon Acipenser baerii

The role of growth hormone (GH) in chondrosteans is poorly understood, particularly with regard to its effects on growth. In this study, we examined the influence of exogenous GH on growth performance and body composition in juvenile Siberian sturgeon (Acipenser baerii). Fish with initial weight of 80.2 ± 0.1 g (mean ± S.E) were injected once every 10 days with either purified ovine GH (oGH) at 1, 2, 4, and 8 μg oGH/g body weight (BW) or with saline over a 50-day period. Treatment with the highest dose of oGH significantly enhanced growth performance (final body weight and length, body weight increase and specific growth rate, SGR). Notably, 8 μg oGH/g BW increased body weight by 33% and SGRw by 141% compared to control fish. GH-stimulated (8 μg oGH/g BW) growth was accompanied by increased crude protein content; however, oGH treatment did not affect levels of total protein, total lipid, cholesterol, triglyceride, or glucose in plasma. oGH decreased plasma levels of thyroxine (at 4 μg oGH/g BW), but had no significant effect on plasma levels of triiodothyronine or cortisol compared to controls. These findings indicate that 8 μg oGH/g BW enhances somatic growth and synthesis of body protein in juvenile Siberian sturgeon and demonstrate the feasibility of exogenous oGH treatment in conservation and aquaculture programs for this ancient species.

Physiological responses to air exposure stress in Siberian sturgeon ( Acipenser baerii Brandt 1869) injected with dexamethasone

Stress can unfavorably affect fish health in hatcheries and it is important to understand how different stressors can change stress response. Dexamethasone (DEX), a synthetic glucocorticoid hormone, shows biological effects in response to stressor conditions. This study was performed to examine the effect of intraperitoneal injection of DEX on the stress response of Siberian sturgeon (Acipenser baerii), an important chondrostean species for aquaculture. For this purpose, one hundred juvenile Siberian sturgeon (average weight 279.0 ± 46.1 g [mean ±SD]) were distributed in two treatments: (1) DEX (1 mg DEX kg−1 body weight) and (2) physiological saline solution as control. 2-min air exposure was applied as an acute stressor. Blood samples were taken before injection and 0.5, 1, 2, 3, 6, 12 and 24 h post-stress. Cortisol levels showed an increasing trend in control treatment and a significant difference was found between control and DEX-treated fish. The highest levels of cortisol in DEX treatment (40.6 ± 0.4 ng mL−1) was recorded at 0.5 h after stress, then showed a decline and finally reached to basal level (24.2 ± 0.7 ng mL−1) at 24 h. The highest glucose (118.0 ± 2.9 mg dL−1) and lactate (125.0 ± 20.8 mg dL−1) values was found at 3 h post-stress in DEX-treated sturgeon and showed significant difference compared with control treatment (glucose: 84.5 ± 2.6 mg dL−1 and lactate: 56.8 ± 17.9 mg dL−1). After 24 h, glucose and lactate concentrations were returned to the basal level in both treatments. Our results showed that the injection of 1 mg DEX kg−1 BW to Siberian sturgeon has a potent role on stress response and describe an inhibitory effect on plasma cortisol following acute stress under laboratory condition.

Dietary lipid levels affect growth, feed utilization, lipid deposition, health status and digestive enzyme activities of juvenile Siberian sturgeon, Acipenser baerii

A 10-week experiment was conducted to evaluate the effects of dietary lipid levels on growth, feed utilization, lipid deposition, health status and digestive enzyme activities of juvenile Siberian sturgeon (Acipenser baerii). Six isonitrogenous diets were formulated with lipid levels at 51.1 (L5), 88.7 (L9), 129.6 (L13), 169.3 (L17), 208.4 (L21) and 248.8 g/kg (L25). The sturgeons fed with L17 had the highest growth and feed utilization. Higher dietary lipid obtained significantly lower PPV than that of L17 (p < .05). Based on WGR, PPV, the optimal dietary lipid was estimated at 169.9, 176.0 g/kg. The lipid deposition in the whole body, muscle and liver enhanced significantly as the dietary lipid increased (p < .05). Dietary lipid levels affected serum biochemical parameters, with the highest AST, TC, LDL-C and LDL-C/TC in L21 or L25 group and highest HDL-C in the L17 group. Serum antioxidants, oxidants and liver MDA content maintained upward trends with increasing dietary lipid from 51.1 to 248.8 g/kg (p < .05). Lipase activity in the spiral valve intestine increased when dietary lipid rose from 51.1 to 169.3 g/kg, but declined when lipid level up to 208.4 and 248.8 g/kg (p > .05). To sum up, the optimal dietary lipid was 169.9–176.0 g/kg for juvenile Acipenser baerii.

Combined effects of enzymes and probiotics on hemato-biochemical parameters and immunological responses of juvenile Siberian sturgeon (Acipenser baerii)

A 10-week feeding trial was run to investigate the separate and simultaneous effects of exogenous enzymes (Enz), probiotics (Pro), and Pro-Enz mixtures on the hematology indices, serum biochemical parameters, and innate-immunity status of juvenile Siberian sturgeon. The fish (138.06 ± 3.64 g) were randomly dispersed into 12 tanks (20 individuals per tank) and fed with Enz (Phytase, protease, and xylanase), Pro (Pediococcus pentosaceus and Lactococcus lactis), and Pro-Enz cocktail. At the end of the feeding bioassay, the highest values of red blood cell count, hemoglobin concentration, hematocrit level, and lymphocyte percentage followed by the lowest neutrophil percentage were obtained in Pro-Enz treatment (P < 0.05). Despite a significantly lower level of alkaline phosphatase in the fish fed with Pro supplemented diet (P < 0.05), no significant difference was found in the serum level of alanine aminotransferase and aspartate aminotransferase among the experimental groups (P > 0.05). Total protein content was significantly upregulated in serum and skin mucus samples from those fed with supplemented diets compared to the control group (P < 0.05). In both serum and skin mucus samples, higher immune responses in terms of lysozyme activity, immunoglobulin M, total protein was seen in Pro-Enz treatment compared to the control group followed by the serum complement components (P < 0.05). The results indicate that the combinational supplementation of Siberian sturgeon diet with the exogenous enzymes and probiotics modulates the physiometabolic responses and innate immune system to a higher grade than their individual supplementation.

Relationship between cortisol and glucose as physiological stress indicators during growth season in juvenile Siberian sturgeon Acipenser baerii

The relationship between cortisol and glucose was studied in two-year old farmed Siberian sturgeon Acipenser baerii with a body weight of 340±30 g (mean ± SD) and total length of 45±1 cm from August to November 2017. Thirty-six individuals were randomly selected and stocked in some 3×300 L fiberglass tanks. Blood samples were collected monthly from the tagged fish. The mean cortisol in August, September, October and November were 4.7±0.9, 23.5±3.0, 6.3±0.9 and 7.4±0.9 ng mL–1 respectively whereas glucose concentrations were 44.6±0.4, 27.3±0.6, 49.2±0.7 and 48.5±0.7 mg dL–1 respectively indicating a significant increase in cortisol and decrease in glucose in September, may be due to the exposure to prolonged high temperature (26–28.5°C). Although it was expected to happen naturally due to hyperglycemia of cortisol but no such phenomena was detected. Our results suggest that the consumption of glucose for maintenance of homeostasis and physiological status is a mechanism against the non-optimal thermal regime. This mechanism consumes glucose at a rate higher than that produced by cortisol, causing significant decrease of plasma glucose. In general, there was a reverse relationship between cortisol and glucose concentration during the experiment in Siberian sturgeons.

Stimulatory effects of short-term calcitonin administration on plasma calcium, magnesium, phosphate, and glucose in juvenile Siberian sturgeon Acipenser baerii.

Calcitonin (CT) has a potential function in calcium (Ca) regulation, but there are conflicting observations in fishes. Because of the lack of calcified endoskeleton, sturgeons have low Ca circulating compared with teleost fish and the function of CT on Ca in sturgeon is very less understood. The purpose of this study was to investigate the impact of injection of salmon CT on plasma Ca, magnesium (Mg), phosphate (PHO), and glucose levels of juvenile Siberian sturgeon Acipenser baerii. Sixteen-month-old fish (429.6 ± 12.1g) were intraperitoneally injected with a single dose of CT (5μgkg-1 BW) and saline solution as a control group. Thereafter, blood sampling was performed at 0, 1, 2, 4, 6, 12, 24, and 48h after injection. CT produced marked increases in all variables measured. The highest levels of Ca (6.77 ± 0.53mgdL-1), Mg (9.79 ± 0.16mgdL-1) and PHO (1.74 ± 0.05mgdL-1) were recorded at 2h after CT injection and showed significant difference compared with control treatment (Ca 4.75 ± 0.12mgdL-1; Mg 5.47 ± 0.16mgdL-1 and PHO 1.23 ± 0.06mgdL-1). It also likely produced hyperglycemia. However, the differences with the controls were not statistically significant, possibly due to interference with the hyperglycemia induced by the stress of injection. Our results showed that the injection of 5μgkg-1 BW CT to Siberian sturgeon has an incremental effect on plasma Ca, Mg, and PHO. The increase in plasma Ca level indicated that CT has a potent hypercalcemic effect in sturgeon under laboratory condition, in contrast to the hypocalcemic effects reported for teleosts.

Quantitative dietary copper requirement of juvenile Siberian sturgeon, Acipenser baerii , and effects on muscle composition and some enzymatic activities

Quantitative dietary copper requirement of juvenile Siberian sturgeon, <i>Acipenser baerii</i> , and effects on muscle composition and some enzymatic activities

Effect of Dietary Inorganic Copper on Growth Performance and Some Hematological Indices of Siberian Sturgeon Acipenser baerii Juveniles

AbstractThis research work was conducted to evaluate the effect of dietary copper (Cu) levels on growth performance, feed utilization, and some hematological parameters of juvenile Siberian Sturgeon Acipenser baerii. Five semipurified diets containing 0, 3, 6, 12, and 24 mg Cu/kg in the form of copper sulfate pentahydrate (CuSO4·5H2O) were formulated to provide the actual dietary copper values of 1.8, 5.7, 10.1, 15.9, and 28.3 mg Cu/kg diet, respectively. The obtained results exhibited a significant improvement in the final weight, protein efficiency ratio, daily growth coefficient, and hepatosomatic index with increasing dietary copper levels up to 10.1 mg/kg diet, while the feed conversion ratio significantly decreased. Also, erythrocyte count, hemoglobin, and hematocrit values increased with increasing levels of dietary copper, but no steady trend was observed in mean corpuscular hemoglobin changes. Furthermore, the neutrophils were significantly increased with enhancing the copper level in the fish diet, while the lymphocytes declined. Findings of the current research illustrate that an appropriate dietary copper level is required for improvement of growth performance, oxygen transfer capability, and white blood cell proliferation. Based on the broken‐line regression analysis of leukocyte count and monocyte percentage, the optimum dietary copper supplementation was estimated to be 10.63 and 10.36 mg Cu/kg diet, respectively.

Physiological responses to feed restriction and starvation in juvenile Siberian sturgeon Acipenser baerii (Brandt, 1869): Effects on growth, body composition and blood plasma metabolites

An 8-week study was applied to evaluate the effects of feed restriction and starvation on growth, proximate composition, haematological and biochemical factors in juvenile Siberian sturgeon Acipenser baerii with an average weight of 54 ± 0.6 g. Fish were randomly divided into nine indoor tanks (1,050 L volume) with 30 fish per tank in a flow-through system at 18 ± 0.4°C. Three feeding strategies were considered: I) fed at satiation (F), II) restricted feeding at the rate of 1% body weight per day (R) and III) starvation (S) each with 3 replicates. Fish were fed with commercial pellets 4 times daily, but no feed was considered for S group throughout the trial. Basal level at the start, 4 and 8 weeks after initiation of the experiment, blood samples were taken from 5 fish/tank to measure the haematological and biochemical parameters. Moreover, growth performance was recorded every 2-week interval. At the end of the experiment, the growth parameters and proximate composition were significantly different among the treatments. As expected, the highest weight (164.7 ± 2.1 g) was observed in F group compared to R (101 ± 1.7 g), or S (42.4 ± 0.8 g) groups. The highest (12.07 ± 0.14%) and lowest (5.37 ± 0.42%) fat contents were observed in F and S groups, respectively, while the protein was not affected in R group compared with F group. In addition, most haematological and biochemical indices of Siberian sturgeon were affected by starvation at week 4 and 8, while few changes were observed in restricted feeding. The highest mean corpuscular volume, mean corpuscular haemoglobin, plasma total protein, cholesterol and triglyceride was found in S group, while the lowest value of plasma glucose was observed in this group. It can be concluded that Siberian sturgeon adjusts the physiological condition in short-term (4 weeks) feed restriction using stored metabolites to have basal metabolism and due to this, a short period of feed restriction strategy recommends to the optimum nutritional management of Siberian sturgeon to cost-saving during unsuitable conditions.

Compensatory growth, plasma hormones and metabolites in juvenile Siberian sturgeon ( Acipenser baerii , Brandt 1869) subjected to fasting and re‐feeding

A 7‐week study was conducted to investigate the effect of different fasting and re‐feeding regimes on compensatory growth and some physiological parameters of juvenile Siberian sturgeon (Acipenser baerii). Fish (46.5 ± 0.5 g) were fed on a diet (containing 450 g/kg crude protein and 20 MJ/kg digestible energy) according to four feeding regimes in triplicate including: control group (C, fed everyday), W1 (2 weeks of feeding followed by 1 week of fasting and 4 weeks of re‐feeding), W2 (1 week of feeding followed by 2 weeks of fasting and 4 weeks of re‐feeding) and W3 (3 weeks of fasting followed by 4 weeks of re‐feeding). The fasted groups including W1 (119.6 ± 2.1 g), W2 (118.0 ± 1.7 g) and W3 (108.5 ± 4.8) significantly lost their weights during fasting phase and did not attain the final weight of the C (137.3 ± 1.7 g) after re‐feeding phase. The re‐feeding phase increased the specific growth rate in the fasted groups compared to the C (p < .05). After the fasting phase, concentrations of T₃, T₄, glucose, total protein and triglyceride in plasma of fasted groups were decreased, but levels of total cholesterol, aspartate aminotransferase, alkaline phosphatase and lactate dehydrogenase increased compared to the C. After re‐feeding phase, except for glucose level, all mentioned metabolites were restored in the plasma of W1 group, but total protein level and aspartate aminotransferase concentrations in plasma were not restored in W2 and W3 groups. Overall, our finding demonstrated 4 weeks of re‐feeding was too short to induce full compensatory growth in A. baerii juveniles.

Effects of insect diets on the gastrointestinal tract health and growth performance of Siberian sturgeon (Acipenser baerii Brandt, 1869)

BackgroundInsects in the fish diet are a natural source of protein, fat, and other nutrients. These meals are considered an ecological replacement for fishmeal to improve growth parameters. The application of insect meals to fish diets has been studied, especially in continental fish. Data regarding the effects of insect meals on the gut health of Siberian sturgeon are not available. This study investigated the effects of full-fat Hermetia illucens (HI) and Tenebrio molitor (TM) meals on the gut health of juvenile Siberian sturgeon. Growth performance, gastrointestinal tract (GIT) histomorphology and the microbiome composition of juvenile Siberian sturgeon were analyzed.ResultsThe inclusion of insect meals did not affect the growth performance or the survival rate. In the gastrointestinal tract histomorphology, a reduction in the mucosa thickness with the HI treatment was observed. In contrast, fish fed the TM diet had an increase in the thickness of the muscular layer. There were no observed significant differences in villus height among treatments. The analysis of the selected microbiota populations in the Siberian sturgeon gastrointestinal tract showed that insect addition affected the composition of the microbiome. The greatest effect on bacterial populations (Clostridium leptum subgroup, Enterobacteriaceae, Clostridium coccoides – Eubacterium rectale cluster, Aeromonas spp., Bacillus spp., Carnobacterium spp., Enterococcus spp. and Lactobacillus group) was observed with the HI diet (P < 0.05). The TM-based diet increased counts in the following bacterial groups: Clostridium coccoides – Eubacterium rectale cluster, Bacillus spp., Carnobacterium spp., and Enterococcus spp. In contrast, the TM diet decreased the total number of bacteria. The TM diet did not significantly affect the Clostridium leptum subgroup, Enterobacteriaceae, Aeromonas spp. or the Lactobacillus group.ConclusionsFish meal replacement by the inclusion of 15% of full-fat Hermetia illucens and Tenebrio molitor (15%) meals did not affect the growth performance, survival rate or villus height of juvenile Siberian sturgeon. The present study suggests that an H. illucens-based diet positively affects the gut microbiota composition and intestinal morphology of juvenile Siberian sturgeon without negative changes in the villus height.

Growth performance and physiological changes of holding juvenile Siberian sturgeon at different sizes in rearing units

An investigation was accomplished to find the effects of different sizes as a social stress on physiological responses and growth performance of Siberian sturgeon. Juvenile Siberian sturgeon were separated into two sizes (860.88 ± 22.32 g as larger fish and 427.28 ± 2.97 g as smaller fish). Three treatments including large size (L), small size (S), and mixed size (M) were considered. There were equal numbers of large and small fish in the M treatment. Sampling was carried out at 1st week (as a short-term sampling) and 8th week (as a long-term sampling) of the experiment. At the end of each sampling, haematocrit, glucose, cholesterol, triglyceride, total protein, lactate, and cortisol were measured. All growth parameters and feed utilization in large fish were not affected in the M treatment compared with the L treatment and also small fish in the M treatment compared with the S treatment. The final biomass in the S treatment was significantly higher than those in the L and M treatments. Haematocrit, glucose, cholesterol, triglyceride, total protein, lactate, and cortisol in the 1st week showed no significant difference with different sizes. However, in the 8th week, only haematocrit increased (by time not size) in the S treatment. Fish in the M treatment in both sizes did not experience the stress condition. Larger and smaller sizes had a positive social interaction; therefore, different sizes of Siberian sturgeon can maintain together without decreasing growth rate and also adverse physiological responses.

Prediction of apparent protein digestibility by in vitro pH-stat degree of protein hydrolysis with species-specific enzymes for Siberian sturgeon (Acipenser baeri, Brandt 1869)

In the present study in vivo apparent protein digestibility (APD) and in vitro degree of protein hydrolysis (DPH; pH-stat assay) of numerous feed ingredients (n = 10) were investigated in juvenile Siberian sturgeon (290 ± 22 g). The ingredients included: fish meal (FM; Clopeonella), meat and bone meal (MBM), poultry by-product meal (PBM), spray dried blood meal (BM), feather meal (FeM), solvent extract soybean meal (SBM), canola meal (CM), corn gluten meal (CGM), wheat gluten meal (WGM), and bakers' yeast (BY). APD values of the ingredients varied from 60 to 92.9% (feather meal and fish meal, respectively). APDs lower than 70% were found in blood meal (68.5%), soybean meal (66.2%), bakers' yeast (66%), canola meal (61%) and feather meal (60%). Also, the ingredients indicated APD values higher than 70%; corn gluten meal (74.3%), wheat gluten meal (76.9%), poultry by-product meal (83.1%) and meat and bone meal (85.6%). Higher DPH values (> 5%) were observed for fish meal, poultry by-product meal and wheat gluten meal; mid-range DPH values (3–5%) for corn gluten meal, meat and bone meal, soy bean meal, blood meal, bakers' yeast; and lower DPH values (<2%) for canola meal and feather meal. Linear regressions between in vivo APD and in vitro degree of DPH with enzyme extracts in feed ingredients for Siberian sturgeon resulted in a considerable correlation (R2 = 0.89–0.99). Also, linear regressions between APD and DPH suggested a close relationship between peptide bond breakage by pyloric caeca and intestine digestive enzymes and the ADP. As a result, this may be a useful tool to provide important nutritional information.

The effect of time-dependent protein restriction on growth factors, nonspecific immunity, body composition, fatty acids and amino acids in the Siberian sturgeon (Acipenser baerii)

The effect of time-dependent protein restriction (PR) and refeeding were investigated on growth, body composition, fatty acids (FA), amino acids (AA) and nonspecific immune functions in the juvenile Siberian sturgeon (Acipenser baeri; 75 ± 5 g). Test diets included: T1 (control) and T2 fish fed diets containing 400 and 300 g/kg protein respectively during the whole experimental period, T3 (every other day) and T4 (every other week) fish were fed diets containing 300 g/kg protein (PR) and refeeding with diet containing 400 g/kg protein respectively, and T5 fish fed a diet containing 300 g/kg protein for 3 weeks and a diet containing 400 g/kg protein for 5 weeks, were fed to the fish for 56 days by visual satiation. Unlike ration T2 and T5, feeding treatments of T3 and T4 showed an increase in fish growth and body composition (p < 0.05) and they were very close to the control group (p > 0.05). Regarding the fatty acid profile, although the percentage of highly unsaturated fatty acids (HUFA) and polyunsaturated fatty acids (PUFA) declined significantly in the T2 and T5 groups, the saturated fatty acid (SFA) and monounsaturated fatty acids (MUFA) indicated no change among the treatments. In addition, the T2 and T5 groups demonstrated a reduction in essential amino acids (EAA) with a simultaneous increase in nonessential amino acids (NEAAs), which was significant from that of controls and other groups (p < 0.05). In terms of nonspecific immune parameters (serum lysozyme activity and alternate complement activity [ACH50]), treatment 3 has an appropriate result that did not have a significant difference with the control group (p > 0.05), but there was significant difference with other groups (p < 0.05). As a result, the T3 treatment can be used in sturgeon aquaculture practically without any negative impacts on biological or physiological indices.