Disease Resistance In Rainbow Trout Research Articles

Interactive effects of dietary probiotic and succinic acid on the growth performance, digestive enzyme activities, immunomodulation, antioxidative capacity, and disease resistance in rainbow trout (Oncorhynchus mykiss) juveniles

Abstract The current study was carried out to explore the effects of lactofeed (LA) as a multi-strain probiotic and succinic acid (SA) on growth variables, gut lactic acid bacteria count, digestive enzymes, innate immune responses, antioxidant capacity, and resistance against Yersinia ruckeri in rainbow trout juvenile (Oncorhynchus mykiss). Three hundred sixty healthy rainbow trout juveniles (13.21 ± 0.41 g) were randomly divided into twelve tanks (300 L) as four experimental groups. They were fed with basal diet (Control; BD), FT1: BD + 1 g/kg LA, FT2: BD + 5 g/kg SA, and FT3: BD + 1 g/kg LA + 5 g/kg SA for eight weeks. According to the results, final weight (FW), weight gain (WG), protein efficiency rate (PER), and feed conversion rate (FCR) revealed a remarkable discrepancy compared to the control group. In addition, dietary inclusion of LA (FT1 and FT3) significantly increased the specific growth rate (SGR). Dietary supplementation of LA+SA (FT3) remarkably improved total bacteria count (TBC) and amylase activity compared to the un-supplemented group. Gut lactic acid bacteria (LAB) count and digestive protease activity in all supplemented fish were remarkably higher than in un-supplemented gruop. Blood immunological factors including white blood cell (WBC) count, total immunoglobulin content (Ig), and the activity of lysozyme (LYZ), alternative complement pathway (ACH50), and acid phosphatase (ACP) were significantly enhanced in the supplemented groups. Neutrophil (NEU) count, skin mucus Ig and hepatic glutathione peroxidase (GPX) increased in SA (FT2 and FT3) treatments. In addition, monocyte (MON) count and skin mucus LYZ activity significantly elevated following feeding with the FT3 diet. Other immunological parameters of skin mucus including protease activity, alkaline phosphatase (ALP) activity, and ACH50 activity, as well as hepatic superoxide dismutase (SOD) and catalase (CAT) activities increased in fish fed with diets containing LA and/or SA. malondialdehyde (MDA) value was remarkably decreased in all supplemented rainbow trout compared to the fish fed with BD. Disease resistance against Y. ruckeri in fish fed with supplemented diets significantly improved with respect to the results obtained in the control specimens. Overall, dietary LA+SA supplementation was beneficial to improve growth performance, gut LAB count, digestive enzyme activities, innate immune responses, antioxidant capacity, and disease resistance in rainbow trout. According to these findings, 1 g/kg LA + 5 g/kg SA is suggested for adding to rainbow trout diet.

A Novel Postbiotic Product Based on Weissella cibaria for Enhancing Disease Resistance in Rainbow Trout: Aquaculture Application.

Postbiotics are innovative tools in animal husbandry, providing eco-friendly solutions for disease management within the industry. In this study, a new postbiotic product was evaluated for its impact on the health of rainbow trout (Oncorhynchus mykiss). In vivo studies were conducted to assess the safety of the Weissella cibaria strains used in postbiotic production. Additionally, this study evaluated the impact of diet supplementation with 0.50% postbiotics on growth performance during a 30-day feeding trial; the gut microbial communities, immunomodulation, and protection against Yersinia ruckeri infection were evaluated. The strains did not harm the animals during the 20-day observation period. Furthermore, the effect of postbiotics on growth performance was not significant (p < 0.05). The treated group showed a significant increase in acid-lactic bacteria on the 30th day of the feeding trial, with counts of 3.42 ± 0.21 log CFU/mL. Additionally, there was an up-regulation of the pro-inflammatory cytokine IL-1β in head kidney samples after 48 h of feed supplementation, whereas cytokines IL-10, IL-8, INF-γ, and TNF-α were down-regulated. The findings indicate that rainbow trout fed with postbiotics saw an improvement in their survival rate against Y. ruckeri, with a 20.66% survival improvement in the treated group. This study proves that incorporating postbiotics from two strains of W. cibaria previously isolated from rainbow trout into the diet of fish has immunomodulatory effects, enhances intestinal microbial composition, and improves fish resistance against Y. ruckeri.

Effects of dietary common juniper (Juniperus communis) essential oil on growth, immunity, antioxidant status, and disease resistance in rainbow trout, Oncorhynchus mykiss

The main aim of this study is to evaluate the effects of common juniper (Juniperus communis) essential oil (JCEO) on growth, digestive enzymes, biochemical profile, immune and antioxidant system, and liver enzymes in the rainbow trout, Oncorhynchus mykiss. 240 fish (10.63 ± 0.06 g) were fed for 60 days in 12 thanks (20 fish per tank) with experimental diets containing JCEO including: control or T1 (untreated), T2 (fed 0.5% JCEO), T3 (1% JCEO), T4 (2% JCEO). Results revealed an increase in final weight (FW) and weight gain (WG) in all treatments, with a significant difference with the control group (P < 0.05). Feed conversion ratio (FCR) decreased, after addition of JCEO compared to the control group (P < 0.05). Amylase, protease and lipase activity levels increased in all groups (T2, T3 and T4 groups), which were significantly different from the control (P < 0.05). The T2 group had the highest total protein (TP) level in serum compared to the control, and all experimental treatments exhibited a significant difference with the control (P < 0.05). The activity of antioxidant enzymes in serum, superoxide dismutase (SOD) and catalase (CAT) increased compared to the control group, with the highest levels in the T4 group. Inclusion of JCEO to the diet significantly reduced the levels of alkaline phosphatase (ALP) and alanine aminotransferase (ALT) activity in blood compared to the control (P < 0.05). The highest level of serum lysozyme activity and total immunoglobulin (total Ig) were observed in T3 group, which displayed a significant difference with the control (P < 0.05). Serum alternative complement activity (ACH50) increased in the supplemented fish compared to the control (P < 0.05). The fish survival increased after challenge with Yersinia ruckeri in JCEO-supplemented fish. In conclusion, JCEO at dietary level of 1% could improve the nutrient digestion and absorption and provide better growth, as well as reinforce the immune system in rainbow trout.

Integrative mRNA-miRNA interaction analysis associated with the immune response in the head kidney of rainbow trout (Oncorhynchus mykiss) after infectious hematopoietic necrosis virus infection

Rainbow trout (Oncorhynchus mykiss) is an important cold-water fish widely cultivated in China. The frequent occurrence of viral diseases caused by infectious hematopoietic necrosis virus (IHNV) seriously restricted the healthy development of the rainbow trout farming industry. However, the immune defense mechanism induced by IHNV in rainbow trout has not been fully elucidated. In the present study, we detected mRNA and miRNA expression profiles in rainbow trout head kidney after IHNV infection using RNA-seq and identified key immune-related genes and miRNAs. The results showed that a total of 7486 genes and 277 miRNAs were differentially expressed, and numerous differentially expressed genes (DEGs) enriched in the immune-related pathways such as Toll-like receptor signaling pathway, RIG-I-like receptor signaling pathway, NOD-like receptor signaling pathway, cytokine-cytokine receptor interaction, and JAK-STAT signaling pathway were significantly up-regulated, including LGP2, MDA5, TRIM25, IRF3, IRF7, TLR3, TLR7, TLR8, MYD88, and IFN1. Integration analysis identified six miRNAs (miR-141-y, miR-200-y, miR-144-y, miR-2188-y, miR-725-y, and miR-203-y) that target at least six key immune-related genes (TRIM25, LGP2, TLR3, TLR7, IRF3, and IRF7). Further, we verified selected immune-related mRNAs and miRNAs through qRT-PCR and confirmed the reliability of the RNA-seq results. These findings improve our understanding of the immune mechanism of rainbow trout infected with IHNV and provide basic data for future breeding for disease resistance in rainbow trout.

Single cell protein from methanotrophic bacteria as an alternative healthy and functional protein source in aquafeeds, a holistic approach in rainbow trout (Oncorhynchus mykiss) juveniles

Bacterial single cell protein (BSCP) obtained from methanotrophic bacteria was tested as an alternative protein source to fishmeal (FM) in compound diets for rainbow trout (Oncorhynchus mykiss) juveniles (initial body weight, BW = 11.3 ± 0.2 g, mean ± standard deviation). Different levels of FM replacement (0, 25, 50, 75 and 100%) by a BSCP (0, 3.75, 7.5, 11.25 and 15% of Uniprotein® Aqua) were tested in isoproteic (crude protein: 42%) and isolipidic (crude fat: 21%) extruded diets. The trial was divided in two different parts, a nutritional trial that lasted 83 days during which the impact of experimental diets was evaluated in terms of key performance indicators (KPIs) associated to fish growth performance and feed utilization, which was followed by a challenge with a pathogenic bacterium (Aeromonas salmonicida subsp. salmonicida) to evaluate the immunological competence of fish fed the experimental diets (15 days). At the end of the nutritional trial, somatic growth in terms of body weight (BW) responded quadratically (P < 0.05) to the dietary inclusion of BCSP with the lowest BW values (183.4 ± 4.5 g) recorded in fish fed 100% FM replacement with BSCP, whereas the rest of dietary groups showed similar BW values (191.3–201.2 g). Feed intake was not affected by the level of FM replacement by BSCP, whereas feed conversion ratio (FCR) slightly increased with increasing levels of BSCP (P < 0.05), even though the lowest FCR values were found in fish fed 50% FM replacement by BSCP (0.79 ± 0.01) in comparison to the control group (0.81 ± 0.01). When using quadratic linear regression, the optimal dietary FM replacement by BSCP in terms of BW values was estimated as 41.7%. The nutritional quality of the fillet was not altered with experimental diets; all dietary groups showed similar amino acid levels as well as their content in HUFA n-3 and n-6 that remained unaltered (P > 0.05) and lipid nutritional indexes (P > 0.05). No negative effects were observed in the histological organization of the liver nor the proximate intestine, neither in the lipid peroxidation levels nor activity of antioxidative stress enzymes in the liver from fish fed increased inclusion levels of BSCP (P < 0.05). The replacement of FM by the tested BSCP obtained from methanotrophic bacteria did not cause an imbalance or dysbiosis in the intestinal microbiota in rainbow trout regardless of the level of FM replaced. The replacement of FM by BSCP at 50% improved disease resistance in rainbow trout exposed to furunculosis when compared to the control diet (cumulative mortality = 83.3 ± 7.2% vs. 49.2 ± 15.6%; P < 0.05), which suggested that this ingredient may also have some immunomodulatory properties that would protect fish from infections, although their mode of action deserves further attention. Current results indicated that the tested BSCP from methanotrophic bacteria is a safe, functional, and sustainable alternative protein source for aquafeeds.

Dietary flaxseed (Linum usitatissimum) oil supplementation affects growth, oxidative stress, immune response, and diseases resistance in rainbow trout (Oncorhynchusmykiss).

This paper describes the effects of flaxseed (Linum usitatissimum) oil (FSO) as a feed additive on growth performance, oxidative stress, immunity, and disease resistance in rainbow trout (Oncorhynchus mykiss). Eight-hundred-and-forty rainbow trout individuals (mean weight: 25.66±1.33g) were fed with different doses of FSO (0.5, 1, and 1.5%) ad libitum two times a day for 9 weeks. At the end of the feeding, growth performance was evaluated and the fish were challenged with two different bacteria (Yersinia ruckeri and Aeromonas hydrophila). At the end of the 3rd, 6th, and 9th weeks, blood and tissue samples were taken from 9 fish per treatment to evaluate innate immune response, cytokine gene expression levels, antioxidant enzyme activities and lipid peroxidation levels, and digestive enzyme activities. Determination of haematological parameters and histological examination was also carried out to evaluate the general health status of the fish. Results showed that the final weight and specific growth rate of FSO-supplemented fish increased significantly (p<0.05). FSO-supplemented fish showed higher resistance to Y. ruckeri than the control group (p<0.05). However, survival rates of all groups in A. hydrophila challenge test were similar (p>0.05). Among the investigated innate immune response parameters, the potential killing activity of phagocytes, myeloperoxidase activity, and lysozyme activity increased in the FSO-supplemented groups (p<0.05). Almost all cytokine gene expression levels in the experimental groups up-regulated especially after 9 weeks of feeding in the head kidney and intestine (p<0.05). Similarly, superoxide dismutase and catalase activities were found to be significantly higher in the FSO group than in the control (p<0.05) whereas, the lipid peroxidation levels drastically declined as a result of the FSO supplementation (p<0.05). These results suggest that FSO can improve growth, enhance immune response, and lower oxidative damage in rainbow trout when supplemented at the rates of 0.5-1.5% for 9 weeks.

Effects of Dietary Sage, Myrtle and/or Probiotic Mixture on Growth, Intestinal Health, Antioxidant Capacity, and Diseases Resistance of Oncorhynchus mykiss

It is widely known that the use of medicinal plants and probiotics as feed additives has a positive effect on growth, non-specific immune system, and resistance to diseases in aquaculture. This study examines the effects of dietary supplementation with sage (Salvia officinalis) and myrtle (Myrtus communis), alone or in combination with a probiotic mixture (PM) on growth, intestine microflora and histology, some antioxidant enzymes activities in the muscle tissues of rainbow trout (Oncorhynchus mykiss) and disease resistance against Vibrio anguillarum. For this purpose, fish were fed with a control diet of 1% sage, 1% myrtle, 1.1% probiotic mixture, 1% sage +1.1% PM and 1% myrtle+1.1% PM supplemented diets for 60 days. At the end of the trial, the fish fed the diets supplemented with myrtle and sage + PM showed a positive effect on feed conversion ratio. According to the histological assessment, the villi length, villi width and goblet cell numbers in the intestines of fish in all groups increased compared to the control. Superoxide dismutase activity in the muscles of fish in the PM group was higher than the fish in the other groups (p&amp;lt;0.05). The malondialdehyde activity was unaffected with the exception of the fish in the sage group (p&amp;lt;0.05). The lactic acid bacteria count in the intestines increased in fish fed the sage + PM (p&amp;lt;0.05). Fish fed the diets supplemented with sage + probiotic mixture, probiotic mixture, myrtle + probiotic mixture, and myrtle saw a significant reduction in mortality (0-32.5%) due to V. anguillarum compared to the control (63.2%) (p&amp;lt;0.05). In conclusion, the use of probiotics, sage and myrtle in combination as a feed supplement showed a positive effect on the growth performance, intestinal microflora and histology, and antioxidant enzymes activities and disease resistance in rainbow trout.

Addition of Chlorella sorokiniana meal in the diet of juvenile rainbow trout (Oncorhynchus mykiss): Influence on fish growth, gut histology, oxidative stress, immune response, and disease resistance against Aeromonas salmonicida

This study aimed to assess the effects of dietary addition with Chlorella sorokiniana on fish growth, gut histology, antioxidant capacity, immune response, and disease resistance in rainbow trout. Three diets with similar proximate composition and different Chlorella meal levels were formulated. The control diet, 5% Chlorella diet, and 10% Chlorella diet contained 0%, 5% Chlorella meal, and 10% Chlorella meal, respectively. Each diet was assigned to triplicate tanks containing 30 fish (165.3 ± 0.6 g) in each tank. Fish were fed experimental diets for ninety days. The results showed that the addition of 5% Chlorella in the diet significantly increased feed intake by 19.3% and weight gain rate by 17.3% (P < 0.05) without affecting feed efficiency and gut histology. Diets containing Chlorella meal significantly decreased malonaldehyde contents in the plasma after the lipopolysaccharide (LPS) challenge (P < 0.05). Dietary supplementation with Chlorella meal significantly increased lysozyme (LZM) activity levels (in the head kidney) and immunoglobulin M (IgM) (in the head kidney) and complement component 3 (C3) (in the spleen) contents before the LPS challenge, and simultaneously increased LZM activity levels (in the plasma) and C3 contents (in the plasma and head kidney) after the LPS challenge (P < 0.05). Furthermore, dietary administration of Chlorella meal significantly increased the survival rate of fish infected with Aeromonas salmonicida (P < 0.05). In conclusion, C. sorokiniana can be used to improve fish growth, antioxidant capacity, and immunity.

Beneficial effects of a sodium butyrate source on growth performance, intestinal bacterial communities, digestive enzymes, immune responses and disease resistance in rainbow trout (Oncorhynchus mykiss)

Beneficial effects of a sodium butyrate source on growth performance, intestinal bacterial communities, digestive enzymes, immune responses and disease resistance in rainbow trout (Oncorhynchus mykiss)

Partial Substitution of Fish Oil with Microalgae (Schizochytrium sp.) Can Improve Growth Performance, Nonspecific Immunity and Disease Resistance in Rainbow Trout, Oncorhynchus mykiss.

Simple SummaryThe global price of fish oil continued to increase due to a consistent downward production trend. Therefore, research on the replacement of fish oil is growing and the search for sustainable alternative sources in aquaculture. The present study was conducted to evaluate dietary microalgae, Schizochytrium sp. (SC) as fish oil replacer in rainbow trout, Oncorhynchus mykiss. Our results suggested that dietary SC is well-digested and could replace up to 80% of fish oil in the diet of rainbow trout without negative effects on growth and immune responses.The price of fish oil has reached a historical peak due to a consistent downward production trend, and therefore, the search for sustainable alternative sources has received great attention. This research was conducted to evaluate dietary micro-algae, Schizochytrium sp. (SC) as fish oil (FO) replacer in rainbow trout, Oncorhynchus mykiss. In the first trial, apparent digestibility coefficient (ADC) was 92.4% for dry matter, 91.4% for crude protein, and 94.2% for crude lipid in rainbow trout. In the second trial, six diets were formulated to replace FO at 0% (CON), 20% (T20), 40% (T40), 60% (T60), 80% (T80), and 100% (T100) with SC in the rainbow trout (3.0 ± 0.4 g, mean ± SD) diet. After eight weeks’ feeding trial, weight gain (WG), specific growth rate (SGR), and feed efficiency (FE) of fish fed the T20 diet were significantly higher than those of fish fed other diets (p < 0.05). However, there were no significant differences in these parameters among those of fish fed CON, T40, T60, and T80 diets. Lysozyme activity of fish fed the T20 diet was significantly higher than those of fish fed other experimental diets (p < 0.05). After 10 days of disease challenge testing with pathogenic bacteria (Lactococcus garvieae 1 × 108 CFU/mL), the cumulative survival rate of fish fed the T20 diet was significantly higher than those of fish fed the CON, T80, and T100 diets. Therefore, these results suggest dietary microalgae SC is well-digested and could replace up to 80% of fish oil in the diet of rainbow trout without negative effects on growth and immune responses.

Evaluation of the ability of Pichia guilliermondii to improve growth performance and disease resistance in rainbow trout (Oncorhynchus mykiss)

AbstractThis study examined supplementation of a novel yeast product containing Pichia guilliermondii on juvenile rainbow trout, Oncorhynchus mykiss, growth, and disease resistance. In two separate trials, fish (initial weight 6.2 and 10.6 g, respectively), were fed an extruded diet (41% digestible protein and 18% crude lipid) supplemented with 0.3 or 0.6% P. guilliermondii alone or 0.3% P. guilliermondii with a dietary gut supplement at 0.1%. Prior to the end of each trial, a subsample of fish from each tank was exposed by immersion to Yersinia ruckeri (Trial 1) or injection with Flavobacterium pyschrophilum (Trial 2). At the conclusion of the trials, supplementation of either P. guilliermondii or the gut supplement improved growth and food conversion efficiency in rainbow trout when fed for 16‐weeks. No effects of supplementation on mortality were observed. These results suggest potential as functional additives; however, additional investigation regarding the efficacy of whole‐cell and disrupted wall components of P. guilliermondii is needed to better assess their potential effects on rainbow trout immune responses.

Growth performance, immune response, antioxidant capacity and disease resistance against Yersinia ruckeri in rainbow trout ( Oncorhynchus mykiss ) as influenced through singular or combined consumption of resveratrol and two‐strain probiotics

In the current study, the possible synergistic properties of resveratrol (Res) and two-strain probiotics (Pro; Lactobacillus acidophilus and Bifidobacterium bifidum) on growth performance, innate immune responses, antioxidant defence and disease resistance against Yersinia ruckeri were assayed in rainbow trout. Accordingly, fish (10.42 ± 0.26 g) were fed with a basal diet as control and diets supplemented with R1 (400 mg/kg Res), R2 (800 mg/kg Res), P1 (0.5 g/kg Pro), P2 (1 g/kg Pro), R1P1 (400 mg/kg Res + 0.5 g/kg Pro) and R2P2 (800 mg/kg Res + 1g/kg Pro) for 8 weeks. The final weight, weight gain and feed conversion rate significantly improved in fish fed the P1, P2, R1P1 and R2P2 (p < .05), after 8 weeks. Diets containing R1P1 and R2P2 significantly elevated the total leucocyte count, and percentages of monocyte and neutrophil at the end of the 8th week (p < .05). Serum complement activity, lysozyme activity and bactericidal activity (BA) of fish fed the diets containing P1, P2, R1P1 and R2P2 were higher than the control group. Oral administration of R2P2 remarkably increased mucus immune parameters (lysozyme, BA, alkaline phosphatase and total immunoglobulin) (p < .05). Moreover, the highest activity of catalase, superoxide dismutase and glutathione peroxidase, and the survival rate were recorded in the R2P2 group. In conclusion, R2P2 remarkably elevated growth performance, innate immune and antioxidant responses, and disease resistance in rainbow trout.

Dietary supplementation with dandelion (Taraxacum officinale) flower extract provides immunostimulation and resistance against Streptococcus iniae infection in rainbow trout (Oncorhynchusmykiss)

Dandelion flower is a well-known phytomedicine due to its therapeutic effects on dyspepsia, bile duct disorders, spleen and liver complaints, and inflammatory diseases. This study aimed to assess the effect of dietary dandelion flower extract (DFE) on skin mucosal and humoral immunity, immune-related gene expression, and disease resistance in rainbow trout. The fingerlings (N = 300, 20.1 ± 0.9 g) were randomly assigned to 15 tanks and fed with different levels of DEF including 0 (control), 1, 2, 3, and 4 g/kg for 56 days. At the end of the trial, the total leukocyte and lymphocyte counts were significantly enhanced in DFE-added groups compared to the control group. Complement components, immunoglobulin M, total protein, and lysozyme showed significantly higher values in the fish treated with dietary DFE at 3 g/kg than others (P < 0.05). The enzymatic activities of the skin mucus samples in the fish fed dietary levels of DFE were significantly higher than the control fish. Skin mucus protein was also improved significantly in 2 and 3 g/kg DFE compared to others. The transcription levels of interleukin-1β and interleukin-6 genes were up-regulated in the fish fed with 3 and 4 g/kg DFE. Interleukin-8 and lysozyme gene expression levels were elevated in 3 g/kg DFE group compared to the control group. Fish mortality after challenging with Streptococcus iniae was significantly reduced from 43.33% in the control group to 73.33% in 3 g/kg DFE group. This study confirmed the beneficial effects of DFE as an immunostimulant in rainbow trout diet and the recommended dose of DFE is 2.49–2.74 g/kg based on the polynomial regression models.

Dietary effect of Ziziphora clinopodioides extract on zootechnical performance, immune response, and disease resistance against Yersinia ruckeri in Oncorhynchus mykiss

An eight-week feeding experiment was performed to determine the potential effects of Blue Mint Bush, Ziziphora clinopodioides, extract (ZE) on growth, digestive enzymes activity, immune response (serum and mucus), and disease resistance in rainbow trout. Accordingly, 450 fish (21.19 ± 1.09 g) were divided into five groups and fed with the experimental diets including: ZE 0% (control diet), ZE 0.5 %, ZE 1.5 %, ZE 3% and ZE 4.5 %. The administration of ZE, except ZE 0.5 %, significantly increased weight gain and specific growth rate compared to the control group (p < 0.05). The highest and lowest digestive enzymes activity (lipase, protease, and amylase) were observed in ZE 3% and the control group, respectively. The results indicated a significant improvement in the number of leucocytes as well as neutrophils and lymphocytes in fish fed with ZE 3 % diet (p < 0.05). The highest serum lysozyme, ACH50, Ig, levels were recorded in ZE 3 %, while the lowest values were obtained in the control group (p < 0.05). Also, serum bactericidal activity in fish receiving ZE 1.5, 3, and 4.5 % showed a significant difference with the control group (p < 0.05). Mucus lysozyme, bactericidal activity, and Ig values in ZE 3 % were higher than the control group (p < 0.05); while there was no significant difference in alkaline phosphatase level (p> 0.05). The highest survival rate (56 %) was recorded in the fish fed with ZE 3 % when the fish were exposed to Yersinia ruckeri on 15 days. Collectively, our results demonstrated that ZE-enriched diets, especially at the level of 3 %, supported growth performance, digestive enzyme activity, non-specific immune system, and resistance to Y. ruckeri infection in fry rainbow trout.

The potential benefits of Lactobacillus farraginis and Enterococcus durans , isolated from kefir, as probiotic candidates on innate immune responses, expression of some immune genes, and resistance to Lactococcosis disease in juvenile rainbow trout

The present research has investigated the effect of Lactobacillus farraginis (LF) and Enterococcus durans (ED), isolated from kefir, as probiotic on innate immune parameters and expression of IL-1β and TNF-1α lysozyme genes in the intestine, as well as resistance to the Lactococcosis in rainbow trout. Four hundred and eighty juveniles (41.9 ± 2.4 g) were divided into eight groups with three replications, including the control, LF1 and LF2 supplemented with 107and 108 Cfu/g feed of each strain, Bactocell equivalent to 1010, ED1 and ED2 with 107 and 108 Cfu/g feed of each strain, combination supplements LF1+ED1 and LF2+ED2 with 5 × 106 and 5 × 107Cfu/g feed of each strain. Compared to control, a significant increase (p < 0.05) was observed in in serum lysozyme, ACH50, C3 and C4, total antibody, bactericidal activities and blood phagocytosis in LF2, Bactocell, LF2+ED2, and ED2 treatments. Besides, lysozyme gene expression in the intestinal tissue of fish treated with LF2, ED2, and Bactocell significantly increased (p < 0.05). A significant increase in TNF-1α gene expression was also observed in all treatments except LF1 and ED1 (p < 0.05). Moreover, a significant increase in the level of IL-1β gene expression was observed in all groups, except for ED1 and LF1+ED1, in comparison to the control treatment. After challenge with Lactococcus garvieae, the lowest mortality percentages were recorded for LF2, Bactocell, LF2+ED2, and ED2 treatment compared to the control. The results suggest beneficial effects of kefir derived LAB strains on immune responses, immune-related genes expression, and disease resistance in rainbow trout.

Yeme İlave Edilen Sumak (Rhus coriaria L.)’ ın Gökkuşağı Alabalıkları (Oncorhynchus mykiss)’ nın Spesifik Olmayan Bağışıklık Tepkisi, Hematoloji ve Vibrio anguillarum’ a Karşı Direnç Üzerine Etkisi

This study aimed to investigate the effects of sumac (Rhus coriaria L.) fruit powder in different concentrations as feed additives on non-specific immune response, hematology, and the disease resistance in rainbow trout (Oncorhynchus mykiss). Fish (35.67±0.88 g) were fed with experimental diets (1.0, 3.0, 5.0 and 10.0 g kg-1) at four different concentration. There were no significant differences between groups fed with sumac fruit powder and control group by the mean of red blood cell count (RBC), white blood cell count (WBC), differential leukocytes count (monocyte, lymphocyte, and neutrophile), hematocrit (Hct), hemoglobin (Hb), cell hemoglobin (MCH pg), cell hemoglobin concentration (MCHC %), cell hemoglobin volume (MCV µm3) and plasma lysozyme, Immunoglobulin M (IgM), total protein level on the 8 weeks. After 8 weeks of feeding, fish were challenged with Vibrio anguillarum and cumulative mortality was recorded over 21 days. Dietary administration of 1.0, 3.0, and 5.0 g kg−1 sumac fruit powder significantly increased fish survival rate (p&amp;lt;0.05). The 10.0 g kg−1 diet received fish showed no mortality post challenged with V. anguillarum. These results showed that the sumac fruit powder improved disease resistance when added to the rainbow trout diet

Synbiotic feed supplementation significantly improves lipid utilization and shows discrete effects on disease resistance in rainbow trout (Oncorhynchus mykiss)

Enteric redmouth disease caused by the bacterial pathogen Yersinia ruckeri is the main reason for antimicrobial prescription, and a cause of substantial economic losses and decreased animal welfare in aquaculture. Given the importance of the intestinal microbiota in digestion and disease, our aim was to investigate whether synbiotic feed supplementation strategies could improve feed performance and disease resistance. Four experimental synbiotic feeds formulated with pre- and probiotics were tested against a commercially available probiotic control feed. Each experimental feed was evaluated for feed performance, effects on gross as well as intestinal morphometrics, and finally their effect on resistance against a waterborne experimental infection with Yersinia ruckeri serotype O1, biotype 2. While co-supplementing Pediococcus acidilactici with citrus flavonoids or bacterial paraprobiotics significantly improved utilization of feed lipid content relative to the control group, a decrease in lipid utilization was observed for feeds that combined P. acidilactici with yeast paraprobiotics. No significant improvements on disease resistance were observed. Still, synbiotic formulations including P. acidilactici led to reduced risks relative to that of the control group, while an increased relative risk was observed for a Bacillus-based formulation. In conclusion, two of the synbiotic supplements significantly improved lipid utilization and contributed to minor increases in disease resistance.

Infectious hematopoietic necrosis virus truncated G protein effect on survival, immune response, and disease resistance in rainbow trout.

The major antigenic protein of infectious hematopoietic necrosis virus (IHNV) is the surface glycoprotein G, which contains neutralizing epitopes that induce the production of immune neutralizing antibodies. In this study, the IHNV G gene sequence was truncated according to bioinformatics principles and then recombinantly expressed via an E. coli expression system. We then assessed the specific antibody immunoglobin M (IgM) levels of rainbow trout immunized with recombinant truncated G protein (emulsified with Freund's incomplete adjuvant), and showed that antibody IgM levels of immunized fish were significantly higher than in the control group (p < 0.01). The mRNA expression levels of interferon 1 (IFN1) and interleukin-8 (IL-8) were also up-regulated significantly (p < 0.01) in head kidneys and spleens of rainbow trout immunized with recombinant truncated G protein. Also, after challenge with wild-type IHNV HLJ-09 virus on Day 28, rainbow trout immunized with recombinant truncated G protein showed cumulative survival rates of 60%. These results indicate that the truncated G protein of IHNV expressed by the E. coli prokaryotic expression system can be used as a candidate immunogen for an IHNV subunit vaccine, which lays a theoretical foundation for the study of further potential IHNV subunit vaccines.

Growth performance, haematological changes, immune response, antioxidant activity and disease resistance in rainbow trout (Oncorhynchus mykiss) fed diet supplemented with ellagic acid

The present study was performed to investigate the effects of various levels of dietary ellagic acid (EA) on growth performance, haematological values, immune response, protection against Yersinia ruckeri infection, and oxidant/antioxidant status in rainbow trout, Oncorhynchus mykiss. Fish were fed with the control diet and three different experimental diets containing three graded levels of EA (50, 100 and 200 mg kg−1 diet) for 8 weeks. At the end of the experiment, the growth performance [weight gain (WG), specific growth rate (SGR) and feed conversion ratio (FCR)], haematological values [the red blood cell (RBC) count, haemoglobin (Hb) concentration, haematocrit (Ht) level and erythrocyte indices: mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC)], immune response [white blood cell (WBC) count, oxidative radical production (nitroblue tetrazolium (NBT) assay), phagocytic activity (PA) and phagocytic index (PI), total protein (TP) and immunoglobulin M (IgM) levels, serum bactericidal activity (BA), lysozyme (LYZ) and myeloperoxidase (MPO) activities] and oxidant/antioxidant status [tissue malondialdehyde (MDA) levels and superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities] were analysed. In addition, fish were challenged by Y. ruckeri and survival rate was recorded for 14 days. In the groups fed with EA the growth parameters such as WG, SGR, and FCR did not vary significantly. The RBC count, Hb concentration, and Ht level increased in the groups fed with EA when compared with the control group. However, there were no significant differences in the MCV, MCH and MCHC values among the groups. The results demonstrated enhancement in all the immunological parameters in the groups fed with EA compared to the control group. The results obtained from challenge with Y. ruckeri revealed reduction in the mortalities in the groups fed with EA. The dietary EA stimulated the SOD, CAT and GSH-Px activities in liver, head kidney and spleen as compared to the control group; however, a reverse trend was observed in the MDA levels of tissues. The present study suggest that EA can effectively enhance the haematological values, immune response, antioxidant capacity, and disease resistance in rainbow trout.

Effects of dietary administration of water hyacinth (Eichhornia crassipes) leaves extracts on innate immune parameters, antioxidant defence and disease resistance in rainbow trout (Oncorhynchus mykiss)

The present trial investigated the effects of dietary administration of (WLEA) and (WLEM) as an immunostimulant on non-specific immune parameters, antioxidant defence and resistance against Streptococcus iniae in rainbow trout (Oncorhynchus mykiss) fingerlings (4.8 ± 0.2 g). One group fed un-supplemented diet compared with six groups fed WLEA and WLEM supplemented diets at different levels (2.5, 5, 10 g/kg). At the middle (28th) and end of feeding trial (56th) as well as 24-h post challenge, several serum innate immune parameters; lysozyme (LYZ), total immunoglobulin (Ig), alternative complement activity (ACH50) and respiratory burst activity (RBA) as well as antioxidant defence parameters; superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) were evaluated. The results indicated that administration of WLE supplemented diets could significantly increase the immune and antioxidant parameters in 28th, 56th and 24 h post challenge (P < 0.05). On the 56th, serum immune parameters increased significantly in many groups compared with 28th (P < 0.05). Also, 24-h post challenge, a significant increase in Ig, ACH50 and RBA activity was observed in most of WLE supplemented groups compared normal condition. No significant increase of antioxidant parameters observed in many groups on 56th compared 28th as well as 24-h post challenge compared normal condition (P > 0.05). Fish fed 1% WLEM and 1% WLEA supplemented diets exhibited increased immune response and antioxidant capacity compared other groups (P < 0.05). The results of challenge test showed that administration of WLE supplemented diets significantly increased trout resistance (P < 0.05); the highest survival rate, was observed in the 1 % WLEM group. The present results confirmed the beneficial effects of WLE as an immunostimulant on rainbow trout and the best result was obtained in fish fed 1% WLEM supplemented diet.