Trout Blood Research Articles

Effect of replacing fish meal with soy protein concentrate on hematological and biochemical blood parameters in rainbow trout (Oncorhynchus mykiss)

The results of assessing the effect of replacing fish meal with soy protein concentrate at 10, 17, 24 and 30% of feed weight on hematological and biochemical parameters of rainbow trout blood are presented. According to the results of clinical and gross anatomy examination, it was found that soy concentrate at 24 and 30% of feed weight led to both a decrease in cavity fat accumulation and intestinal hyperemia, which may indicate the onset of intestinal inflammation. At lower concentrations (10 and 17% of feed weight), no such changes were detected in the intestine. Experiments showed that soy concentrate at 24 and 30% of feed weight increased the number of neutrophils and monocytes in the fish blood, while decreasing the leukocyte count. Lower doses of soy concentrate had no effect on hematological parameters. The key change in blood biochemical parameters was an increase in aspartaminotransferase activity and serum protein (albumin and globulin) concentrations, observed in the groups fed higher doses of soy concentrate. Preliminary data suggest that incorporating soy concentrate at 24 and 30% of feed weight may impair rainbow trout physiological parameters due to altered amino acid composition and the presence of anti-nutritional factors. However, soy concentrate had no observable effect on growth; all experimental groups exhibited similar growth dynamics.

Comparative analysis of the biochemical composition of rainbow trout blood serum under different feeding diets

Rational and efficient feeding of aquaculture objects is one of the foundations of production in highly productive fish farming. The aim of the study was to compare the composition of production compound feeds for aquaculture objects and to study the effect of compound feeds on the biochemical parameters of the blood serum of rainbow trout. To achieve the aim of the study, 10 groups of rainbow trout (Parasalmo mykiss (Walbaum, 1792) of the "Rofor" breed) grown in production conditions of cage farms in Karelia were selected. Alanine transferase, aspartate aminotransferase, alkaline phosphatase, total protein, albumins, creatinine, urea, glucose, total bilirubin and total cholesterol were determined in the blood serum of the studied individuals. The obtained result has an important practical significance since with excessive intake of carbohydrates these fish develop liver glycogen overload syndrome due to insufficient insulin production. Therefore, the optimal carbohydrate content for them is 20-30%, including 5-6% fiber. In this case, monosaccharides are used better - glucose, fructose, mannose, somewhat worse - disaccharides and starch, and cellulose is broken down only by 10-20% of the consumed. In addition, it is necessary to take into account that trout, as a cold-loving fish, cannot use carbohydrates in the same volume as heat-loving objects of aquaculture, therefore, in order to save protein, which can be used for energy purposes, it is necessary to additionally introduce fats into their diets. However, in the studied compound feeds this component did not meet the GOST standards. The results of the conducted research can be used to optimize the composition of production feed for rainbow trout and to register background ichthyohematological criteria for the quality of keeping highly productive aquaculture species.

Effect of β-glucans on rainbow trout (Oncorhynchus mykiss) IgM+ B cells

β-glucans are carbohydrates present in the cell wall of many fungi, which are often used as immunostimulants in feeds for farmed species. Their capacity to activate innate immune responses directly acting on innate cell populations has been widely documented in fish. However, whether they can affect the functionality of adaptive immune cells has been scarcely explored. In this context, in the current work, we have determined the effects of β-glucans on rainbow trout blood IgM+ B cells in the presence or absence of 2,4,6-trinitrophenyl hapten conjugated to lipopolysaccharide (TNP-LPS), a model antigen. For this, rainbow trout peripheral blood leukocytes were incubated with different doses of β-glucans or media alone in the presence or absence of TNP-LPS for 48 h. The size, levels of expression of surface MHC II, antigen processing and phagocytic capacities and proliferation of IgM+ B cells were then studied by flow cytometry. The number of IgM-secreting cells in the cultures was also estimated by ELISpot. β-glucans significantly decreased the levels of surface MHC II expression and the antigen processing capacities of these cells, especially in the presence of TNP-LPS, while they increased their phagocytic activity. On their own, β-glucans slightly activated the proliferation of IgM+ B cells but reduced that induced by TNP-LPS. In contrast, β-glucans significantly increased the number of cells secreting IgM in the cultures. This effect of β-glucans on the IgM-secreting capacity of B cells was also confirmed through a feeding experiment, in which the IgM-secreting capacity of blood leukocytes obtained from fish fed a β-glucan-supplemented diet for one month was compared to that of leukocytes obtained from fish fed a control diet. Altogether, these findings contribute to increase our knowledge regarding the effects of β-glucans on fish adaptive responses.

Influence of protein concentrates in compound feeds on hematological parameters of fish

In the field of feeding aquaculture objects, it is important to search for alternative feed sources. The purpose of the research was to evaluate the effect of high-protein feed concentrates on the growth performance and hematological composition of rainbow trout. Research was carried out At the enterprise IP Kalmykova I. O. in order to study the protein concentrate Gorlinka in compound feed for rainbow trout. The trout of the control group were fed compound feed with sunflower meal, and the fi sh of the 1st, 2nd and 3rd experimental groups were fed compound feed in which sunflower meal was replaced with Gorlinka concentrate – 50 %, 75 and 100 %, respectively, for the groups. Research on the introduction of the protein concentrate Agro-Matic into the compound feed of rainbow trout was carried out under the conditions of the Scientifi c Research Center “Breeding of valuable sturgeon breeds” of the Volgograd State Agrarian University. The fish of the control group received the main diet with fish-meal, and in the diet of the trout of the 1st, 2nd and 3rd experimental groups, 25 %, 50 and 75 % of fish-meal were replaced with Agro-Matic concentrate. It was found on the base of results obtained that the introduction of Gorlinka concentrate into the compound feed formulation contributed to the increase in the overall gain in live weight of fi sh by 2,83–6,93 %. The use of Agro-Matic concentrate in compound feed had a positive effect on the live weight of fish; it increased by 1,29–5,26 %. The content of total protein in the blood serum of fish from the experimental groups relative to the control increased by 0,65 %, 1,64 and 3,27 % with the introduction of the Gorlinka concentrate into the diet, and the Agro-Matic protein concentrate by 1,01 %, 2,44 and 3,55 %, respectively, which is due to balance of the recipes. When studying some indicators of fish blood we found that with a balanced diet the biochemical composition of trout blood is quite constant and is within the physiological norm for salmon fish.

Polyphenol-rich extracts enhance growth, immune function, and antioxidant defense in juvenile rainbow trout (Oncorhynchus mykiss).

The present study was conducted to investigate the effects of PMIX, a polyphenol-rich extract mixture from chestnut wood and olive, on growth performance, hematological parameters, immunity in serum and skin mucus, hepatic antioxidant enzymes, and intestinal cytokine expression in rainbow trout (Oncorhynchus mykiss). Four experimental diets containing 0 g PMIX kg-1 diet (control, C), 0.5 g PMIX kg-1 diet (P0.5), 1 g PMIX kg-1 diet (P1), and 2 g PMIX kg-1 diet (P2) were fed to rainbow trout in an eight-week feeding trial. Triplicate groups of fish received each treatment. Growth performance, feed conversion ratio, protein efficiency, hepatosomatic and viscerosomatic indices, hematological parameters, immunity markers, hepatic antioxidant enzyme activities, and intestinal cytokine expression were determined. PMIX supplementation significantly improved feed conversion ratios, while groups P0.5 and P1 evidenced an increase in growth performance along with protein efficiency ratios. It also showed decreased hepatosomatic and viscerosomatic indices in the P1 group. Except for higher percentages of monocytes in P0.5 and P1, most hematological parameters of the fish did not differ from that of the control. Serum lysozyme and respiratory burst activities were heightened in all PMIX-treated groups, and the skin mucus lysozyme activity was enhanced in P1. The blood phagocytic activity and phagocytic index, serum immunoglobulin, total protein, and bactericidal activity against A. hydrophila did not change. Hepatic superoxide dismutase activity significantly increased in P1 and P2, even though catalase activity did not change. Intestinal interleukin-6 expression was upregulated in all PMIX-treated groups, while tumor necrosis factor-alpha and interleukin-1 beta were upregulated in P1, P2, and P0.5 respectively. The present results evidence that dietary polyphenols from chestnut wood and olive extracts enhance growth performance, antioxidant capacity, and several immunological parameters in the blood, skin mucus, and intestine of rainbow trout. A suitable supplementation level was 1 g PMIX kg-1 diet to separate these improvements.

Respiratory acidosis and O2 supply capacity do not affect the acute temperature tolerance of rainbow trout (Oncorhynchus mykiss).

The mechanisms that determine the temperature tolerances of fish are poorly understood, creating barriers to disentangle how additional environmental challenges-such as CO2-induced aquatic acidification and fluctuating oxygen availability-may exacerbate vulnerability to a warming climate and extreme heat events. Here, we explored whether two acute exposures (~0.5hours or ~72hours) to increased CO2 impact acute temperature tolerance limits in a freshwater fish, rainbow trout (Oncorhynchus mykiss). We separated the potential effects of acute high CO2 exposure on critical thermal maximum (CTmax), caused via either respiratory acidosis (reduced internal pH) or O2 supply capacity (aerobic scope), by exposing rainbow trout to ~1kPa CO2 (~1% or 10 000 μatm) in combination with normoxia or hyperoxia (~21 or 42kPa O2, respectively). In normoxia, acute exposure to high CO2 caused a large acidosis in trout (blood pH decreased by 0.43units), while a combination of hyperoxia and ~1kPa CO2 increased the aerobic scope of trout by 28%. Despite large changes in blood pH and aerobic scope between treatments, we observed no impacts on the CTmax of trout. Our results suggest that the mechanisms that determine the maximum temperature tolerance of trout are independent of blood acid-base balance or the capacity to deliver O2 to tissues.

A novel combination of non-thermal plasma process and a heterogenous nanophotocatalyst-sorbent comprising zinc sulfide, graphene oxide and polyaniline as an efficient strategy for treatment of organic-contaminated water

A dielectric barrier discharge (DBD) reactor was designed in the present study to generate non-thermal atmospheric pressure Ar plasma. A heterogeneous p-n-p visible-driven photocatalyst comprising ZnS, Graphene oxide, and Polyaniline (ZGP) was also synthesized via chemical polymerization. A novel combination of photocatalyst and plasma treatment was then developed for the synergetic removal of organic pollutants from aqueous solutions. The addition of the p-n-p photocatalyst (5 mg) to the dye solution (malachite green, 50 mL, 20 mg/L) under plasma radiation resulted in a 97 % removal rate in 12 min. Scavenging studies confirmed a decline in the effectiveness of the reactive species in the following order: OH• > e־ > O2־• > h+. The changes in surface chemistry of the recovered photocatalyst were probed by XPS, and possible involved reactions were suggested. The synergetic factor of 1.53 in this system was a remarkable achievement comparable with the records of air or oxygen plasma reactors. The absence of hazardous by-products was confirmed by GC–MS and AAS techniques. The treated aqueous solution was utilized to evaluate its effect on lentil seed growth and trout blood factors, which led to promising results with several advantages but no negative effects.

Squalene Supplementation as a Novel to Increase PUFA Content in Fish Tissues.

Squalene is an antioxidant that plays an essential role in fat metabolism. The study aimed to assess the effect of squalene supplied in feed on the growth performance, health status, and fatty acid profiles of muscle and liver of Siberian sturgeon, rainbow trout, and Eurasian perch. The experimental feeds containing 0%, 0.5%, and 1.0% squalene were prepared for each fish species. Hematological and biochemical indices, liver histology, and fatty acid profiling of muscle and liver were analyzed. Squalene supplementation was safe for fish, and no negative influence on growth status was observed. However, changes in the values of hematological and biochemical indicators were found, including the level of triglycerides in the blood of rainbow trout, and cholesterol in the blood of Eurasian perch. The addition of squalene influences the nucleocytoplasmic index values in all fish offered feed containing 1% squalene. The retention of squalene in the liver and muscle of experimental Siberian sturgeon was observed in both 0.5% and 1.0% squalene levels of feed. The PUFA and docosahexaenoic acid increase was observed in all fish in groups with squalene addition. Dietary squalene increases the content of PUFAs in tissues of the examined species.

Novel insights into the cytokine network of rainbow trout Oncorhynchus mykiss using cell lines and primary leukocyte populations

Cytokines are small proteins that regulate innate and adaptive immune responses and are released by both immune and non-immune cell types. In the current study, the constitutive and induced gene expression profiles of a suite of proinflammatory and regulatory cytokines was examined comparatively in eight rainbow trout (Oncorhynchus mykiss) cell lines, in order to establish the cytokine repertoires of these different cell types, especially the understudied non-immune cells. They included three epithelial cell lines (RTgut, RTgill, and RTL), one endothelial cell line (RTH), one fibroblast cell line (RTG-2), two stromal cell lines (TSS and TPS-2) and one monocyte/macrophage-like cell line (RTS-11). Three types of primary leukocytes (derived from blood, spleen and head kidney) of trout were also included in the analysis, to allow comparison to the repertoires expressed in T cells, as a major source of cytokines in immune responses. The major findings are: 1) IL-2A, IL-2B, IL-4/13B1, IL-4/13B2, IL-10b, P40B1, P28B, IL-17A/F1b, TNF-α3, TNF-α4, IFNγ1, CCL20L2b and CCL20L3a are expressed mainly in leukocytes but IL-17 N, IL-17D, IL-20 and CCL20L1b2 are not expressed in these cells. Hence future studies in these cell lines will help establish their function in fish; 2) Some of the cytokines were differentially expressed in the cell lines, revealing the potential role of these cell types in aspects of trout mucosal and inflammatory immune responses, 3) Similar cell types grouped together in the cell cluster analysis, including the leukocyte cluster, stromal cell cluster, and epithelial and endothelial cell cluster. Taken together, this investigation of these trout cell lines forms a good database for studying the function of cytokines not expressed in isolated leukocytes or that are preferentially expressed in the cell lines. Furthermore, the cytokine expression analysis undertaken confirmed the phenotypic relationship of these cell types at the molecular level.

СРАВНИТЕЛЬНАЯ ХАРАКТЕРИСТИКА КОРМОВ ПО БИОХИМИЧЕСКИМ ПОКАЗАТЕЛЯМ СЫВОРОТКИ КРОВИ ONCORHYNCHUS MYKISS (WALBAUM, 1792)

The main reasons for the decrease in feeding efficiency are dietary inadequacy and poor quality of the feed, which leads to its suboptimal consumption and accumulation of residue, which, in turn, results in deterioration of the hydrochemical regime. This study presents the comparative analysis of two fish feeds in terms of their safe use for Oncorhynchus mykiss (Walbaum, 1792) feeding and their impact on water quality. The investigation was conducted on the rainbow trout individuals in the recirculating aquaculture system at the Aquaculture Center of the K.G. Razumovsky Moscow State University of Technologies and Management in 2021-2020 and involved the comparison of the feeds CRYSTAL (protein content 42.65 %) produced by Alltech Coppens and Basic PL 45/20 A50 (protein content 45.81 %) produced by BNBC (Belarusian National Biotechnology Corporation). Six test groups were included in the experiment: three groups were fed with Alltech Coppens CRYSTAL and the other three groups were fed with BNBC Basic PL compound feed. The biochemical characteristics of the rainbow trout blood serum have been identified using the blood taken from a caudal vein, and the hydrochemical characteristics of the water have been identified using standard procedures. A distinct relationship between the protein content in Oncorhynchus mykiss blood serum and protein content in the feeds has been found. The hydrochemical characteristics of the water in the recirculating aquaculture system over the course of the experiment remained within the normal range, with exception of iron that had been present before the experiment and did not have an adverse effect on the fish’s health.

Oxidative Stress Biomarkers in the Blood of Rainbow Trout (Oncorhynchus mykiss Walbaum) and Equine Plasma after Incubation with Hemp Oil "Annabis Bio"

Industrial hemp is a multi-use crop that has been widely cultivated to produce fibers and nutrients, such as protein, dietary fiber, minerals, and unsaturated fatty acids, which make them a good fortifying component in food production. The antioxidant capability of hemp oils has been reported. In the current study, for evaluating the antioxidant activity of commercial hemp oil "Annabis BIO" derived from certified industrial hemp seeds without the psychoactive substance THC (Olomouc, Czech Republic), biomarkers of oxidative stress [2-thiobarbituric acid reactive substances (TBARS), oxidatively modified proteins (OMP), total antioxidant capacity (TAC)] were used in models of the blood collected from adult healthy rainbow trout (Oncorhynchus mykiss Walbaum), the blood of rainbow trout with clinical symptoms of ulcerative dermal necrosis (UDN), and equine plasma. A volume of 0.1 mL of the hemp oil was added to 1.9 mL of fish blood or equine plasma. After incubation of the mixture for 60 min with continuous stirring, biomarkers of oxidative stress were studied in samples. After in vitro incubation of hemp oil with the blood of clinically healthy rainbow trout, we noted a statistically significant decrease in biomarkers of lipid peroxidation by 55.6% (p <0.05). The highest increase in TBARS level was observed after in vitro incubation of hemp oil with the blood of UDN-affected rainbow trout. In vitro incubation of hemp oil with equine plasma resulted in a statistically significant increase in the level of ketonic derivatives (by 29%, p <0.05) and aldehydic derivatives of OMP (by 33.1%, p <0.05). Incubation of hemp oil with the blood of UDN-affected trout resulted in a decrease of the ketonic derivative of OMP (by 43.3%, p <0.05). Incubation of hemp oil with equine plasma, we observed a statistically significant decrease in TAC level by 56.6% (p <0.05). Similarly, after incubation hemp oil with blood samples of UDN-affected trout, a statistically significant decrease in total antioxidant capacity (by 59.3%, p <0.05) was observed. The results suggest that the investigated hemp oil have shown varied antioxidant capacities. Accordingly, this study proposes that the therapeutic benefit of this hemp oil can be, at least in part, attributed to using different biological materials (blood, plasma) used in vitro in the current study.

Analysis of the lake trout heart, blood, liver, and brain proteome using evolutionary proteomics

IntroductionSalvelinus namaycush (lake trout) is a top‐predator fish in the Great Lakes region. The Great Lakes Fish Monitoring and Surveillance Program (GLFMSP) use lake trout as a bioindicator of chemical stress by monitoring the concentrations of persistent, bioaccumulative and toxic (PBT) chemicals in their bodies. Studies have shown that elevated concentrations of PBTs can cause changes in transcribed genes, translated mRNAs, proteins produced, and post‐translational modifications in aquatic species. Though lake trout is used to monitor chemical concentrations for over 50 years, there is very little information available on the proteome of this species. A well‐developed protein database for the lake trout would help elucidate the effects of PBT chemicals on this species providing a direct health metric for the Great Lakes ecosystem.MethodsIn this study, heart, blood, brain, and liver samples from lake trout were analyzed by SDS‐PAGE, followed by in‐gel trypsin digestion and analysis by nanoLC‐MS/MS. The raw data was searched against different NCBI and UniProtKB databases in Mascot Daemon and the output was analyzed by Scaffold 4.3 software. Databases used include Actinopterygii, Salmonidae, Salvelinus, as well as the highly studied species Oncorhynchus mykissand Danio rerio.Preliminary DataPreviously, our group has reported a large number of proteins for lake trout liver, heart and blood (Dupree et al., Proteomics, 2019, PMID: 31578773 and Dupree et al., Proteomics, 2021, PMID: 34676671). In lake trout liver we identified 4194 proteins using the NCBI databases and 3811 potential protein hits in the UniProtKB databases. In the blood and heart we identified 838 and 580 proteins, respectively, using NCBI databases and 1180 and 561 potential protein hits for the heart and blood, respectively in BR2. A lake trout brain proteomics analysis completed using an in‐house SDS‐PAGE, followed by in gel digestion and nanoLC‐MS/MS analysis. The Mascot database search is underway. Once protein hits are cataloged, BLAST and Scaffold‐based comparisons of the liver, heart, blood and brain will be performed. Additional search of the data against the other fish relatives will also be completed. Through this process, evolutionary relationships for the lake trout species will also be explored. The current study will add to our understanding of the lake trout proteome that will be used to understand the biochemical/physiological effects of legacy PBT chemicals in the Great Lakes ecosystem.Novel AspectUse of four types of lake trout tissue together to develop a protein database for the species.

A Multidisciplinary Approach Evaluating Soybean Meal-Induced Enteritis in Rainbow Trout Oncorhynchus mykiss

This study evaluated a diverse range of markers of feeding stress to obtain a more precise assessment of the welfare of rainbow trout in relation to inadequate husbandry conditions. A feeding stress model based on dietary soybean meal was employed to identify suitable minimally invasive “classical” stress markers, together with molecular signatures. In a 56-day feeding experiment, rainbow trout were fed diets containing different levels of soybean meal. The impact of these different soybean meal diets on rainbow trout was assessed by water quality analyses, clinical health observations, classic growth and performance parameters, gut histopathology, blood-parameter measurements and multigene-expression profiling in RNA from whole blood. Soybean meal-induced enteritis was manifested phenotypically by an inflammatory reaction in the posterior section of the intestine and by diarrhoea in some trout. These inflammatory changes were associated with decreased supranuclear vacuolation. The haematocrit values and the levels of plasma cortisol and circulating lymphocytes in the blood were increased in trout that had consumed high amounts of SBM. Notably, the increased haematocrit depended significantly on the bodyweight of the individual trout. The transcript levels of certain genes (e.g., MAP3K1, LYG, NOD1, STAT1 and HSP90AB) emerged as potentially useful indicators in the blood of rainbow trout providing valuable information about inadequate nutrition. The expression-profiling findings provide a basis for improved, minimally invasive monitoring of feeding regimens in trout farming and may stimulate the development of practical detection devices for innovative aquaculture operations.

Anesthesia of rainbow trout with citronellal: Efficacy and biochemical effects.

The aim of this study was to assess the anesthetic efficacy and biochemical effects of citronellal on rainbow trout, Oncorhynchus mykiss. The fish were exposed to 200-800 µl/L citronellal to find the anesthesia induction and recovery times. The deep anesthesia stage was reached within 117-613 s, using 800-200 µl/L citronellal, respectively, and all fish recovered within 240-420 s. To assess biochemical responses, the fish were exposed to 200, 400, 600, and 800 µl/L of citronellal and blood-sampled after deep anesthesia. Theresults showed that anesthesia led to significant elevations in blood erythrocytes, hematocrit, hemoglobin, mean corpuscular volume, plasma lactate, and lactate dehydrogenase; these parameters exhibited increasing trends as citronellal concentration increased. These results along with significantly higher plasma lysozyme activity, cortisol, and glucose levels in 200 µl/L treatment suggest that an increase in citronellal concentration significantly mitigates hypoxia/stress responses in the fish. Significant elevations in plasma alkaline phosphatase activity and malondialdehyde level were observed in the 200 µl/L treatment, which suggests induction of hemolysis and oxidative stress in this treatment. There was a tendency to higher ammonia levels along with the increase in citronellal concentration, which might be due to early ammonia accumulation because of lower opercular movement in the fish. Except for blood hematocrit and mean corpuscular volume, there were no significant differences between the 600 and 800 µl/L citronellal treatments. In conclusion, high concentrations of citronellal are more suitable for trout anesthesia and blood sampling than low concentrations. Based on the present study, 600-800 µl/L citronellal is recommended for trout anesthesia.

Proteomic analysis of the lake trout (Salvelinus namaycush) heart and blood: The beginning of a comprehensive lake trout protein database.

Lake trout (Salvelinus namaycush) are a top-predator species in the Laurentian Great Lakes that are often used as bioindicators of chemical stressors in the ecosystem. Although many studies are done using these fish to determine concentrations of stressors like legacy persistent, bioaccumulative and toxic chemicals, there are currently no proteomic studies on the biological effects these stressors have on the ecosystem. This lack of proteomic studies on Great Lakes lake trout is because there is currently no complete, comprehensive protein database for this species. Here, we employed proteomics approaches to develop a lake trout protein database that could aid in future research on this fish, in particular exposomics and adductomics. The current study utilized heart tissue and blood from two lake trout. Our previous work using lake trout liver revealed 4194 potential protein hits in the NCBI databases and 3811 potential protein hits in the UniProtKB databases. In the current study, using the NCBI databases we identified 838 proteins for the heart and 580 proteins for the blood tissues in the biological replicate 1 (BR1) and 1180 potential protein hits for the heart and 561 potential protein hits for the blood in BR2. Similar results were obtained using the UniProtKB databases. This study builds on our previous work by continuing to build the first comprehensive lake trout protein database and provides insight into protein homology through evolutionary relationships. This data is available via the PRIDE partner repository with the dataset identifier PXD023970.

Hematological and biochemical indicators of rainbown trout blood depending on lysin and methionine levels in feed

The effect of use of complete feed with different lysine and methionine levels on the hematological and biochemical indicators of rainbow trout blood is studied in the article. The aim of the experiment was to establish the effect of different levels of amino acid nutrition of commercial rainbow trout on hematological and biochemical indicators of its blood. For this purpose, five experimental groups were formed by the analog method. The study lasted 210 days and was divided into two periods: equalizing (10 days) and basic (200 days). In the equalizing period, the trial fish consumed feed of the control group. In the basic period of the experiment, the level of lysine and methionine in the production feed ranged from 2.5 to 2.9% and from 0.8 to 1.0%, respectively. It was found that the different content of lysine and methionine in the diets of two-year-old rainbow trout did not cause significant changes in biochemical indicators of blood. The increase in the content of limiting amino acids in the combined feed of young rainbow trout caused slight deviations in hemoglobin content compared to control. The analysis of the obtained results revealed the highest content of erythrocytes (1.28 T/l) in the blood of specimen of experimental group 5, the level of amino acids in combined feeds was the lowest. Its highest content was found in the blood plasma of trout of experimental group 4, which received combined feed with a content of 2.8 % lysine and 0.95 % methionine. The concentration of total protein in the blood serum was almost the same in all experimental groups of commercial rainbow trout. It was found that different levels of amino acid nutrition of rainbow trout did not affect the dynamics of changes in the blood cell morphology differentials.

Diversity of Rainbow Trout Blood B Cells Revealed by Single Cell RNA Sequencing

Simple SummaryAlthough evolutionarily jawed fish constitute the first group of animals in which a complete adaptive immune system based on immunoglobulins (Igs) is present, many structural immune differences between fish and mammals predict important functional and phenotypical differences between B cells in these two animal groups. However, to date, very few tools are available to study B cell heterogeneity and functionality in fish. Hence, thus far, antibodies targeting the different Igs have been almost exclusively applied as tools to investigate B cell functionality in fish. In the current study, we used the newly developed 10× Genomics single cell RNA sequencing technology and used it to analyze the transcriptional pattern of single B cells from peripheral blood. The results obtained provide us with a transcriptional profile at single cell level of what seem to correspond to different B cell subsets or B cells in different stages of maturation or differentiation. The information provided will not only help us understand the biology of teleost B cells, but also provides us with a repertoire of potential markers that could be used in the future to differentiate trout B cell subsets. Single-cell sequencing technologies capable of providing us with immune information from dozens to thousands of individual cells simultaneously have revolutionized the field of immunology these past years. However, to date, most of these novel technologies have not been broadly applied to non-model organisms such as teleost fish. In this study, we used the 10× Genomics single cell RNA sequencing technology and used it to analyze for the first time in teleost fish the transcriptional pattern of single B cells from peripheral blood. The analysis of the data obtained in rainbow trout revealed ten distinct cell clusters that seem to be associated with different subsets and/or maturation/differentiation stages of circulating B cells. The potential characteristics and functions of these different B cell subpopulations are discussed on the basis of their transcriptomic profile. The results obtained provide us with valuable information to understand the biology of teleost B cells and offer us a repertoire of potential markers that could be used in the future to differentiate trout B cell subsets.

Hematological and biochemical indicators of blood of trout depending on energy levels in feed

Hematological and biochemical indicators of blood of trout depending on energy levels in feed

Pretreatment with selenium prevented the accumulation of hexavalent chromium in rainbow trout (Oncorhynchus mykiss) and reduced the potential health risk of fish consumption

Hexavalent chromium (Cr6+) is a toxic element in environment. Selenium (Se) is an essential micronutrient trace element for living organisms and can ameliorate the adverse effects induced by Cr6+. However, the correlations between Se and Cr in fish have been rarely reported. The present study focused on the antagonistic effects of Se on Cr-induced accumulation in tissues (blood, gills, intestines, liver, kidney and muscle) of rainbow trout. Initially, a 42-day feeding trail was conducted as the fish were fed with basal diet supplemented with or without 4 mg/kg Se (as Se-yeast). A remarkable increase of Se in tissues was observed. Se was predominately accumulated in liver and the Se significantly decreased the initial Cr level in liver. Furthermore, after the pretreatment of Se, the fish were exposed to 1 mg/L Cr solution and it could be found that all the tissues showed a significant accumulation of Cr. An exciting result was obtained that the pretreatment of Se could prevent the Cr accumulation in fish muscle and reduced the health risk of fish consuming. A pearson correlation analysis was conducted to examine the relationship between Se and Cr and a significant negative correlation was found in muscle. Overall, it could be concluded that the pretreatment of Se in rainbow trout could effectively prevent the Cr accumulation in muscle, which is beneficial for reducing health risk of fish consumption.

The first record of brook trout (Salvelinus fontinalis, Salmonidae) blood cell characteristics and hematological profile: the influence of fish sex on leukocyte count

Hematological parameters of fish are useful for diagnosing pathophysiological conditions associated with metabolic perturbations in fish and therefore act as a non-specific biomarker of acute and chronic stress in the natural habitat and in aquaculture. Salmonid fish are of great importance in aquaculture; however, hematological studies of these species are scarce. This study presents the first set of data for the complete hematological profile of brook trout (Salvelinus fontinalis, Salmonidae). In total, seven blood cell types were identified and their characterization, range, size/surface area, and the leukocyte differential count are presented. Large numbers of immature erythrocytes and two subtypes of thrombocytes (round and prolate) were present in blood. Lymphocytes were the dominant leukocytes, followed by segmented neutrophils. Total leukocyte and segmented neutrophil counts were higher in the blood of male than female fish (P < 0.05). Here we describe, for the first time, basophilic cells in salmonid fish species. Blood cell types present in brook trout were similar to mammalian blood cells, but their morphology, number, size, and subtypes were unique to this fish species. The established reference model indicates differences in comparison with the cyprinid fish. The hematological profile described in this study will serve as an important model for examining comparative physiology of blood cells in other salmonid fish and will provide useful diagnostic criteria in aquaculture for the detection and mitigation of different pathological outcomes.