Resistance Of Rainbow Trout Research Articles

Dietary Thymol Supplementation Promotes Antioxidant Responses and Thermal Stress Resistance in Rainbow Trout, Oncorhynchus mykiss.

Rainbow trout fingerlings were fed, in triplicate, diets supplemented with 0 (CTL), 50 (50 TM), 100 (100 TM), 200 (200 TM), 400 (400 TM) and 800 (800 TM) mg/kg of thymol, followed by 48 h of thermal stress. Growth performance and humoral immunological parameters showed no significant responses to dietary thymol concentrations. Fish fed 50-400 mg/kg thymol diets had significantly higher survival after heat stress. Plasma cortisol, glucose, hepatic glutathione peroxidase, glutathione reductase and erythrocyte catalase significantly increased after thermal stress, whereas total plasma antioxidant capacity, ascorbate, and hepatic/erythrocyte reduced-glutathione significantly decreased. There were significant elevations in plasma ascorbate and hepatic glutathione reductase in the 50 TM, 100 TM and 200 TM groups; plasma total antioxidant capacity in the 100 TM and 200 TM groups; hepatic glutathione peroxidase in the 200 TM group; and hepatic-reduced glutathione in the 100 TM, 200 TM and 400 TM groups, compared to CTL. The highest hepatic superoxide dismutase and lowest hepatic malondialdehyde were observed in the 100 TM group before heat stress. These parameters significantly increased after thermal stress in the treatment groups, except in the 100 TM and 200 TM groups. Hepatic catalase showed no significant difference among the treatment groups before thermal stress. Hepatic catalase significantly increased after heat stress in all treatment groups, except in the 100 TM group. Erythrocyte superoxide dismutase significantly increased in the 100 TM group before heat stress, whereas erythrocyte malondialdehyde significantly decreased in the 100 TM and 200 TM groups after thermal stress. Based on the results, 100 mg/kg of thymol can promote antioxidant power and thermal stress resistance in rainbow trout.

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 juveniles (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 unsupplemented group. Gut lactic acid bacteria (LAB) count and digestive protease activity in all supplemented fish were remarkably higher than in unsupplemented group. 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 were 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.

Immunological, Antioxidant, Growth Responses, and Disease Resistance of Rainbow Trout, Oncorhynchus mykiss, with Feeding Diets Supplemented with Lactobacillus salivarius and Lutein

Abstract The aim of the present study was to assess the effects of dietary supplementation with Lactobacillus salivarius (LS) ATCC 11741 and lutein (LU) on immunological, antioxidant, and growth responses, and resistance against Yersinia ruckeri infection in rainbow trout (Oncorhynchus mykiss). There were seven experimental diets containing un-supplemented diet (CTL), L. salivarius at 1 × 106 (LS6) and 1 × 108 (LS8) CFU/g, lutein at 50 (LU50) and 150 (LU150) mg/kg, L. salivarius at 1 × 106 CFU/g plus lutein at 50 g/kg (LS6+LU50), and L. salivarius at 1 × 108 CFU/g plus lutein at 150 g/kg (LS8+LU150). These diets were provided to the fish (N= 735; 14.0±0.38 g). After 60 days of feeding, all experimental treatments exhibited significantly higher growth performance, compared to the CTL treatment. The intestinal protease activity and the intestinal lactic acid bacteria population in the probiotic-treated fish were significantly higher than in the CTL fish. The intestinal lipase activity was only higher in the LS6+LU50 treatment, compared to the CTL treatment. Compared to the CTL treatment, the intestinal total bacterial count, and serum superoxide dismutase significantly increased in the LS6+LU50 and LS8+LU150 treatments. The serum catalase significantly increased in LU150, LS6+LU50, and LS8+LU150 treatments, and serum glutathione peroxidase significantly increased in the lutein-treated fish. All experimental treatments, particularly LS6+LU50 and LS8+LU150, had significantly lower serum malondialdehyde levels, compared to the CTL treatment. The levels of serum alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and lactate dehydrogenase in LU50, LS6+LU50, and LS8+LU150 treatments were significantly lower than the CTL. All experimental treatments showed significantly higher serum lysozyme (LYZ), complement, blood respiratory burst activity (RB), and skin mucus alkaline phosphatase (ALP), compared to the CTL treatment. The highest serum LYZ, C4, total immunoglobulin (Ig), blood RB activity, and skin mucus peroxidase, ALP, and Ig were observed in the LS6+LU50 and LS8+LU150 treatments. All the experimental treatments, especially LS6+LU50, exhibited significantly lower mortality after the bacterial challenge compared to the CTL. In conclusion, dietary supplementation with 1 × 106 CFU/g L. salivarius and 50 mg/kg lutein can maximally improve growth performance, digestive enzymes, antioxidant parameters, immune responses, intestinal lactic acid bacteria, and resistance against yersiniosis in rainbow trout.

Molecular mechanism of TRIM32 in antiviral immunity in rainbow trout (Oncorhynchus mykiss)

TRIM family proteins are widely found in multicellular organisms and are involved in a wide range of life activities, and also act as crucial regulators in the antiviral natural immune response. This study aimed to reveal the molecular mechanism of rainbow trout TRIM protein in the anti-IHNV process. The results demonstrated that 99.1 % homology between the rainbow trout and the chinook salmon (Oncorhynchus tshawytscha) TRIM32. When rainbow trout were infected with IHNV, the TRIM32 was highly expressed in the gill, spleen, kidney and blood. Meanwhile, rainbow trout TRIM32 has E3 ubiquitin ligase activity and undergoes K29-linked polyubiquitination modifications dependent on the RING structural domain was determined by immunoprecipitation. TRIM32 could interact with the NV protein of IHNV and degrade NV protein through the ubiquitin-proteasome pathway, and was also able to activate NF-κB transcription, thereby inhibiting the replication of IHNV. Moreover, the results of the animal studies showed that the survival rate of rainbow trout overexpressing TRIM32 was 70.2 % which was significantly higher than that of the control group, and stimulating the body to produce high levels of IgM when the host was infected with the virus. In addition, TRIM32 can activate the NF-κB signalling pathway and participate in the antiviral natural immune response. The results of this study will help us to understand the molecular mechanism of TRIM protein resistance in rainbow trout, and provide new ideas for disease resistance breeding, vaccine development and immune formulation development in rainbow trout.

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.

Dietary supplementation of Chinese herbal medicines enhances the immune response and resistance of rainbow trout (Oncorhynchus mykiss) to infectious hematopoietic necrosis virus.

Rainbow trout is a widely farmed economical cold-water fish worldwide, but the prevalence of infectious hematopoietic necrosis virus (IHNV) presents a severe risk to the aquaculture industry, resulting in high mortality and huge economic losses. In this study, the impacts of different concentrations (0, 10, 20, and 30 g/kg) of Chinese herbal medicine mixture (CHMM) on the immune response and resistance of rainbow trout to IHNV infection were evaluated. The results show that CHMM noticeably increased (P < 0.05) T-SOD, CAT, AST, ALT, ACP, and AKP activities and decreased MDA content. NF-κB, TNF-α, IFN-β, IL-1β, JAK1, HSP70, and HSP90 expressions were significantly upregulated (P < 0.05) in all CHMMs, while SOCS2 expression was downregulated (P < 0.05). Following infection with IHNV, feeding rainbow trout with varying amounts of CHMM resulted in noticeably increased (P < 0.05) T-SOD, ACP, and AKP activities and significantly decreased (P < 0.05) MDA content and AST and ALT activities. TNF-α, IFN-β, IL-1β, HSP70, and HSP90 expressions were significantly upregulated (P < 0.05) in all CHMMs, while the expressions of JAK1 and SOCS2 were downregulated. The expression level of the IHNV G protein gene at a dosage of 20 g/kg was notably lower than that of the other CHMM feeding groups. This study provides a solid scientific basis for promoting CHMM as an immunostimulant for boosting antiviral immunity in rainbow trout.

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.

Effects of black soldier fly meal feeding on rainbow trout gut microbiota, immune-related gene expression, and Lactococcus petauri resistance

Abstract Providing a sustainable and affordable food supply is one of the most significant challenges facing the global aquaculture industry. Black soldier fly (BSF), Hermetia illucens, meal is a particularly promising alternative to animal-derived protein sources. Following a 90-day feeding experiment with four different diets containing BSF meal with increasing fish meal replacement levels of 25%, 50%, 75%, and 100%, designated as B25, B50, B75, and B100, and a control diet (B0) without BSF meal, the gut microbiota, immune-related gene expression, and Lactococcus petauri resistance of rainbow trout (Oncorhynchus mykiss) were studied. Regardless of diet, rainbow trout intestinal microbiota were different from those in water. In the intestinal mucosa, Fusobacteria, Firmicutes, and Proteobacteria were among the most prevalent taxa. Rainbow trout fed with a BSF-containing diet had a higher bacterial diversity in their gastrointestinal tract than fish fed with a control diet. The abundance of Firmicutes, Actinobacteria, and Proteobacteria increased in tandem with the replacement rate of fish meal with BSF meal. The B75-fed fish were found to be the most resistant group to L. petauri, followed by the groups fed with B100, B50, and B25. Compared to the control group, the expression of cytokines (Tgf, Il-10, Il-1β, , and Il-8) and immune-related genes (IgM, IgT, Mhc-II, and Tlr-5) increased significantly () in all fish groups fed with a BSF-containing diet. Substituting fish meal with BSF meal beyond 50% enhanced the survival rates of fish infected with L. petauri. Furthermore, BSF-containing diets boosted the immune system and cytokine-related genes in fish. Due to improved survival and immunity, rainbow trout may be fed a 50% BSF meal substituted diet without removing chitin or pre-treating BSF meal.

Effects of dietary oregano essential oil-mediated intestinal microbiota and transcription on amino acid metabolism and Aeromonas salmonicida resistance in rainbow trout (Oncorhynchus mykiss)

Effects of dietary oregano essential oil-mediated intestinal microbiota and transcription on amino acid metabolism and Aeromonas salmonicida resistance in rainbow trout (Oncorhynchus mykiss)

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.

Rosmarinic acid alone or in combination with Lactobacillus rhamnosus ameliorated resistance to ammonia stress in the rainbow trout, Oncorhynchus mykiss: growth, immunity, antioxidant defense and liver functions

Abstract Rosmarinic acid (RS) and Lactobacillus rhamnosus (LR) were added singularly or in combination to rainbow trout (Oncorhynchus mykiss) diets to test their efficacy in the protection against ammonia stress. Fish (31.4±0.6 g) were randomly allocated to six groups in three replicates, as follows: T1: basic food as control, T2: LR with a concentration of 1.5 × 108 CFU /g, T3: LR with a concentration of 3 × 108 CFU/g, T4: 1 g RS/kg, T5: 3 g RS/kg, and T6: 1.5 × 108 CFU/g LR + 1 g RS/kg and T7: 3 × 108 CFU/g LR + 3 g RS/kg. After 60 days feeding, fish were exposed to ammonia stress. After the feeding period, the supplemented fish had the highest final body weight (FW), weight gain (WG), and specific growth rate (SGR), and the lowest feed conversion ratio (FCR) as compared with the control group (P&lt;0.05). Amylase, protease and lipase activities were noticed markedly higher in fish supplemented with 1.5 × 108 CFU/g LR + 1 g RS/kg and 1.5 × 108 CFU/g LR diets compared to the control (P&lt;0.05). Generally, fish in supplemented diets, particularly T2 and T6 groups, had the highest lysozyme, alternative complement activity (ACH50), total Ig, nitroblue tetrazolium test (NBT), myeloperoxidase (MPO), complement component 3 (C3), complement component 4 (C4), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx). On the other hand, T2 and T6 groups had the lowest malondialdehyde (MDA), glucose, and cortisol concentrations as well as alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) enzyme levels when compared with the control (P&lt;0.05). After ammonia stress, fish in the supplemented groups, particularly T2 and T6, generally showed significantly higher values of lysozyme, ACH50, total Ig, NBT, MPO, C3, C4, SOD, CAT, GPx and lower levels of MDA, glucose, cortisol, ALT, ALP, LDH when compared with the control (P&lt;0.05). In conclusion, a combined administration of RS and L. rhamnosus effectively improved growth performance and health status as well as enhanced the resistance of rainbow trout against ammonia toxicity.

Pot Marigold (Calendula officinalis) Powder in Rainbow Trout (Oncorhynchus mykiss) Feed: Effects on Growth, Immunity, and Yersinia ruckeri Resistance

The current research investigated the effects of pot marigold (Calendula officinalis) powder on growth, biochemical parameters, digestive enzymes, serum and mucus immune responses, antioxidant defense, and resistance of rainbow trout (Oncorhynchus mykiss) against Yersinia ruckeri. Fish (No. 450, 15.06 ± 0.11 g; mean ± SE ) were randomly distributed to five groups fed with a diet containing 0 (control group), 0.5%, 1%, 1.5%, and 2% of pot marigold powder (MP) for 60 days. Then, fish were challenged with Y. ruckeri infection. Specific growth rate (SGR), weight gain (WG), final weight (FW), feed conversion ratio (FCR), mucus lysozyme (LYZ), mucus protease, serum nitroblue tetrazolium test (NBT), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) values in the 1%, 1.5%, and 2% MP groups significantly increased ( P &lt; 0.05 ) compared to the other groups. Regression analysis exhibited that rainbow trout growth indices were polynomially linked to dietary MP concentrations. In this regard, the optimal levels of MP, according to growth parameters (SGR and FCR), were 1.31 and 1.4% diet, respectively. The intestinal protease, serum complement component 3 (C3), complement component 4 (C4), and LYZ activities in fish fed with the 1% and 1.5% MP-supplemented regime were higher ( P &lt; 0.05 ) compared to the other groups. Also, fish fed with diets containing 1.5% MP had significantly higher intestinal lipase and mucus ALP activities than the other groups ( P &lt; 0.05 ). Aspartate aminotransferase (AST) activity in all MP groups remarkably increased ( P &lt; 0.05 ) compared to the control. Moreover, fish fed with a diet containing 1.5% MP had remarkably higher ( P &lt; 0.05 ) lactate dehydrogenase (LDH) and total protein (TP) values than the other groups. Serum myeloperoxidase (MPO), total immunoglobulin (Ig), and mucus peroxidase values in the 1% MP group remarkably increased ( P &lt; 0.05 ) compared to the other groups. In addition, catalase (CAT) and superoxide dismutase (SOD) activities in the 1.5% and 2% MP groups were significantly higher ( P &lt; 0.05 ) compared to the others. However, malondialdehyde (MDA) levels in fish fed with the 1%, 1.5%, and 2% MP-supplemented diet remarkably decreased than in the other groups ( P &lt; 0.05 ). The highest survival rate after a challenge with Y. ruckeri was recorded in the 1.5% group compared to the control group. Our findings revealed that using pot marigold powder in diets, especially at the 1.5% level, has positive effects on growth, digestive enzyme activities, antioxidant capacity, immune response, and disease resistance in O. mykiss.

Effect of Different Levels of Chlorogenic Acid on Growth Performance, Immunological Responses, Antioxidant Defense, and Disease Resistance of Rainbow Trout (Oncorhynchus mykiss) Juveniles.

The current study is designed to assay the efficacy of chlorogenic acid (ChA) in the diet on growth performance, digestive enzyme activity, serum immunological, biochemical, and antioxidant variables, and mucosal immune response as well as disease resistance of rainbow trout (Oncorhynchus mykiss) juveniles. Rainbow trout juveniles received diets supplemented with different inclusion levels of ChA (0 (ctrl), 200 (CA1), 400 (CA2), 600 (CA3), and 800 (CA4) mg kg-1 diet) for 60 days. According to the findings, fish from CA3 and CA4 groups demonstrated the best results considering the final weight (FW) and weight gain (WG) (P < 0.05). Also, the group that received 600 mg kg-1 ChA-supplemented diet showed the lowest feed conversion ratio (FCR) and the highest specific growth rate (SGR) compared to other groups (P < 0.05). Moreover, the minimum survival rate (SR) was only detected in the CA4 treatment (P < 0.05). Regression analysis exhibited that rainbow trout growth indices were polynomially linked to dietary chlorogenic acid concentrations. In this regard, the optimal levels of chlorogenic acid according to growth parameters (FCR and SGR) were 0.71 and 0.62 gr kg-1 diet, respectively. The results exhibited superior performance of protease and amylase activities in CA2, CA3, and CA4 groups with the maximum amount in the group receiving 600 mg kg-1 ChA-enriched diet (P < 0.05). Serum lysozyme (LYZ), immunoglobulin (Ig), and components 3 and 4 (C3 and C4) values of CA2, CA3, and CA4 groups were significantly higher than others with the highest amount in the CA3 group (P <0.05). Additionally, serum nitroblue tetrazolium (NBT) value in the CA3 and CA4 groups and myeloperoxidase (MPO) in the CA3 group were notably more than others (P < 0.05). Moreover, the lowest aspartate aminotransferase (AST), alkaline phosphatase (ALP), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) and the highest total protein (TP) and globulin (GLO) values were observed in CA3 treatment (P < 0.05). CA2 and CA3 groups demonstrated increased serum catalase (CAT) and decreased malondialdehyde (MDA) values compared to the control while the highest CAT and lowest MDA values were observed in CA3 treatment (P < 0.05). Considering mucus immunity, the significantly maximum LYZ and protease values were demonstrated in CA2 and CA3 groups, and the highest ALP, Ig, and esterase values were demonstrated in the CA3 group. In comparison with the control, the mortality rates of the groups that received the ChA diets were remarkably (P < 0.05) lower postchallenge with Y. ruckeri, and the highest survival and relative percentage of survival (RPS) (P < 0.05) belonged to the CA3 group. Results obtained from the current study suggested ChA as a functional dietary additive to raise growth parameters, immune indices, antioxidant capacity, and resistance to disease in rainbow trout.

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.

Identification of Haplotypes Associated With Resistance to Bacterial Cold Water Disease in Rainbow Trout Using Whole-Genome Resequencing.

Bacterial cold water disease (BCWD) is an important disease in rainbow trout aquaculture. Previously, we have identified and validated two major QTL (quantitative trait loci) for BCWD resistance, located on chromosomes Omy08 and Omy25, in the odd-year Troutlodge May spawning population. We also demonstrated that marker-assisted selection (MAS) for BCWD resistance using the favorable haplotypes associated with the two major QTL is feasible. However, each favorable haplotype spans a large genomic region of 1.3–1.6 Mb. Recombination events within the haplotype regions will result in new haplotypes associated with BCWD resistance, which will reduce the accuracy of MAS for BCWD resistance over time. The objectives of this study were 1) to identify additional SNPs (single nucleotide polymorphisms) associated with BCWD resistance using whole-genome sequencing (WGS); 2) to validate the SNPs associated with BCWD resistance using family-based association mapping; 3) to refine the haplotypes associated with BCWD resistance; and 4) to evaluate MAS for BCWD resistance using the refined QTL haplotypes. Four consecutive generations of the Troutlodge May spawning population were evaluated for BCWD resistance. Parents and offspring were sequenced as individuals and in pools based on their BCWD phenotypes. Over 12 million SNPs were identified by mapping the sequences from the individuals and pools to the reference genome. SNPs with significantly different allele frequencies between the two BCWD phenotype groups were selected to develop SNP assays for family-based association mapping in three consecutive generations of the Troutlodge May spawning population. Among the 78 SNPs derived from WGS, 77 SNPs were associated with BCWD resistance in at least one of the three consecutive generations. The additional SNPs associated with BCWD resistance allowed us to reduce the physical sizes of haplotypes associated with BCWD resistance to less than 0.5 Mb. We also demonstrated that the refined QTL haplotypes can be used for MAS in the Troutlodge May spawning population. Therefore, the SNPs and haplotypes reported in this study provide additional resources for improvement of BCWD resistance in rainbow trout.

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)

Dietary nanoselenium supplementation for heat-stressed rainbow trout: effects on organizational structure, lipid changes, and biochemical parameters as well as heat-shock-protein- and selenoprotein-related gene expression

Nanoselenium (nano-Se) shows unique protective effects against environmental heat stress in rainbow trout as a selenium source additive and free radical scavenger. Accordingly, we investigated the effects of supplementation with different levels of nano-Se (0, 5, and 10 mg/kg) and before and after heat stress (24°C) for different treatment times on the dynamic changes of rainbow trout liver tissue structure, lipid changes, biochemical properties, and gene expression. The results showed that, under heat stress, the fish supplementation of 5 mg/kg nano-Se significantly increased liver glutathione peroxidase (GPx) activity and upregulated expression levels of HSP70b, HSP90a1, GPx1a, and Trx mRNAs, while liver alanine aminotransferase (ALT), aspartate aminotransferase (AST), superoxide dismutase (SOD), and malondialdehyde (MDA) levels as well as tissue structure damage and lipid accumulation were decreased. Combining the trends for the above indicators indicated that stress began to increase significantly at 8 h. It can be concluded that supplementation with 5 mg/kg nano-Se effectively alleviates stress damage in rainbow trout. Furthermore, stress at 24°C for 8 h can be thought of as a critical time point for the study of heat stress in rainbow trout, with significant changes in response but no serious damage. Thus, these results provide a reference for the addition of nano-Se to rainbow trout feed and provide theoretical and practical guidance for enhancing the resistance of rainbow trout to heat stress.