Hilyses®, fermented Saccharomyces cerevisiae, enhances the growth performance and skin non-specific immune parameters in rainbow trout (Oncorhynchus mykiss)

Effects of Hilyses^®, fermented Saccharomyces cerevisiae (S. cerevisiae), on growth, body composition and skin mucus immune components in rainbow trout were quantified. Ninety rainbow trout (105 ± 5 g) were randomly assigned to 2 groups in triplicates and fed dietary Hilyses^® (5 g kg^?1) or control diet without Hilyses^® for 50 days. Results of this study demonstrated that growth performance increased significantly by the dietary yeast supplement; however body composition was not affected in treatment group. At the 45th and 50th day of feeding trial, results of mucus samples demonstrated that yeast supplementation in treatment group significantly promoted enzyme activities, namely lysozyme, protease, alkaline phosphatase and esterase compared to control group. Significant increases were also observed in hemagglutination and antibacterial activity against Yersinia ruckeri in fish fed treatment diet. The present study suggests that fermented S. cerevisiae may effectively promote the growth performance and skin non-specific immune parameters in rainbow trout.     

Combined and Singular Effects of Dietary PrimaLac® and Potassium Diformate (KDF) on Growth Performance and Some Physiological Parameters of Rainbow Trout (Oncorhynchus mykiss)

The present study was conducted to assess the effects of combined and singular dietary administration of PrimaLac® and potassium diformate (KDF) on growth performance, feed utilization, digestive enzymes activity, and some physiological parameters of rainbow trout (Oncorhynchus mykiss) juvenile. Three hundred sixty rainbow trout juveniles (25 ± 1.8 g) were randomly stocked in 300-L tanks (30 fish/tank), and fed three times daily on a basal diet (control), diets incorporated with 12 g kg⁻¹ KDF (FT₁), 1.5 g kg⁻¹ PrimaLac® (FT₂), and combination of 1.5 g kg⁻¹ probiotic and 12 g kg⁻¹ KDF (FT₃) in triplicates, for 8 weeks. At the end of feeding trial, growth performance, body composition, digestive enzymes, liver enzymes, and biochemical parameters were measured. Our results revealed that combined administration of PrimaLac® and KDF (FT₃) exhibited significantly higher weight gain and specific growth rate (SGR) compared to other groups (P < 0.05). Glucose and cortisol levels showed no significant differences between fish fed different test diets (P > 0.05). The highest lipase, protease and amylase activity were observed in group of fish fed FT₃ followed by FT₂ and FT₁. Besides, the diets FT₂ and FT₃ led to significantly lower of ALP, ALT, and AST compared to control group. The present results indicated that combined administration of PrimaLac® and KDF can be considered as a beneficial feed additive and growth promotor for O. mykiss juvenile.

     

Effects of Saccharomyces cerevisiae supplementation on immune response,hematological parameters,body composition and disease resistance in rainbow trout,Oncorhynchus mykiss (Walbaum, 1792)

Natural substances are now generally preferred over chemical and synthetic compounds for the growth and immune enhancement of aquatic organisms. The aim of this study was to evaluate the effect of Saccharomyces cerevisiae extract and hydrolyzed powder on immunity, hematological parameters and body composition in rainbow trout, Oncorhynchus mykiss. Six hundred rainbow trout (50 ± 5 g mean weight) were acclimated to laboratory conditions and then randomly divided into four groups of triplicate tanks. The first group was fed with a commercial diet (control) without supplementation. The second and third groups were given a diet supplemented with 1% of yeast extract and hydrolyzed powder, respectively. The fourth group was also fed with a basal diet supplemented with 0.5% of both substances. Fish were cultured in 300‐L polyethylene tanks for 60 days; immune and hematological parameters, fillet composition and disease resistance were analyzed at days 0, 30 and 60. Results showed that a combination of Saccharomyces cerevisiae extract and hydrolyzed powder could improve the immunity and alter hematological parameters of the rainbow trout compared to the control. Mortality rates of fish fed yeast extract and hydrolyzed powder were also lower than in fish fed the control diet after challenging with Yersinia ruckeri. There were no significant changes in rainbow trout fillet composition compared to the control. It can be concluded that fish diet supplementation with a mixture of yeast extract hydrolyzed powder is preferable compared to each one used alone.     

Fucoidan effectively provokes the innate immunity of white shrimp Litopenaeus vannamei and its resistance against experimental Vibrio alginolyticus infection

In this study, we examined the effect of fucoidan on the immune response of white shrimp Litopenaeus vannamei and its resistance against Vibrio alginolyticus infection. Fucoidan induced degranulation, caused changes in the cell morphology, and increased activation of prophenoloxidase (proPO) and the production of superoxide anions in vitro. Shrimp that received fucoidan via immersion at 100, 200, and 400 mg l^?1 after 3 h showed haemocyte proliferation and a higher mitotic index of haematopoietic tissue. In another experiment, the haemocyte count, phenoloxidase (PO) activity, and respiratory bursts (RBs) were examined after the shrimp had been fed diets containing fucoidan at 0 (control), 0.5, 1.0, and 2.0 g kg^?1 for 7–21 days. Results indicated that these parameters directly increased with time. The immune parameters of shrimp fed the 1.0 g kg^?1 diet were significantly higher than those of shrimp fed the 2.0 g kg^?1 diet after 14 and 21 days. Phagocytic activity and the clearance efficiency against V. alginolyticus were significantly higher in shrimp fed the 1.0 g kg^?1 diet compared to those of shrimp fed the 0, 0.5 and 2.0 g kg^?1 diets. In a separate experiment, shrimp that had been fed diets containing fucoidan for 21 days were challenged with V. alginolyticus at 10⁶ colony-forming units shrimp^?1. Survival rates of shrimp fed the 1.0 and 2.0 g kg^?1 diets were significantly higher than those of shrimp fed the 0 and 0.5 g kg^?1 diets for 96–120 h. We concluded that fucoidan provokes innate immunity of shrimp as evidenced by haemocyte degranulation, proPO activation, and the mitotic index of haematopoietic tissue, and that dietary administration of fucoidan at 1.0 g kg^?1 enhanced the immune response of shrimp and their resistance against V. alginolyticus infection.     

Characterization of probiotic properties of lactic acid bacteria isolated from an estuarine environment for application in rainbow trout (Oncorhynchus mykiss, Walbaum) farming

Bacterial attachment to fish surfaces and the capacity to compete with pathogens for adhesion sites are essential characteristics in order to select a candidate probiotic for aquaculture. Twelve lactic acid bacteria (LAB) isolated from fish and sediments from Bahía Blanca Estuary, Argentina, were examined for in vitro adhesion to rainbow trout mucus, cell surface properties and competitive exclusion against two salmonid pathogens, Yersinia ruckeri and Aeromonas salmonicida. In order to assess their survival through the digestive tract, pH and rainbow trout bile tolerance were evaluated. All LAB strains survived for 1.5 h incubation in 10% rainbow trout bile. Most of the strains survived 1.5 h at pH 3.0 and three of them showed a reduction of viable counts lower than 2 logarithms, with respect to control (pH 6.5). Only a few strains showed tolerate pH 2.0. All the strains were able to attach to rainbow trout skin mucus (10⁴–10⁶ cells/cm²), to glass (10⁴–10⁵ cells/cm²) and to stainless steel (10³–10⁴ cells/cm²). Sixty percent of LAB strains were capable of competing with and successfully excluding Y. ruckeri and all strains were able to displace it. Against A. salmonicida, 75% of LAB strains competed successfully, 50% were capable of displacing and 60% excluded this pathogen. Our data suggest the potential of these strains as anti-infective agents for use in rainbow trout culture. This study is the first report on the probiotic potential of LAB strains isolated from an estuarine environment from Argentina.     

Dietary Macrogard reduces <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis> mortality in tench (<Emphasis Type="Italic">Tinca tinca</Emphasis>) through the activation of cellular and humoral defence mechanisms

Influence of beta-1.3/1.6-glucan (Macrogard) on the innate immunity and protection against Aeromonas hydrophila in tench (Tinca tinca (L.)) was assessed. Macrogard was fed at doses of 0, 0.5, 1 and 2 g kg⁻¹ of pellets for 1 month. The blood, spleen and head kidney from 10 fish of each group were separated and analysed for immunity parameters. Twenty tench from each group were infected with A. hydrophila. Macrogard at doses 1 and 2 g kg⁻¹ of feed significantly (P < 0.05) increased the phagocytic activity of macrophages and proliferative response of mitogens stimulated lymphocytes. The same doses significantly (P < 0.05) increased lysozyme activity and Ig level in serum, compared to the control and dose 0.5 g kg⁻¹ of feed. The challenge test showed that Macrogard reduced mortality of tench after experimental infection (5–35%).     

Nutritional value and intake of aquatic ferns (Azolla filiculoides Lam. and Salvinia molesta Mitchell.) in sows

Aquatic ferns (AFs) such as Azolla filiculoides and Salvinia molesta are grown on swine lagoons in the tropics and used in diets for pigs. The present work is aimed at evaluating their potential as feed ingredients for sows. When presented with ad libitum AFs, gilts weighing 110 ± 14 kg (mean ± SD), were able to ingest 9.1–9.7 kg fresh AF per day (from 597 to 630 g dry matter (DM) per day) and from 1240 to 1428 g DM per day when presented in a dry, ground form. A digestibility study was conducted, using sows weighing 213 ± 9 kg (mean ± SD), which were fed diets containing maize, soybean meal and 0, 150 or 300 g AF kg⁻¹ diet. The presence of AFs had a negative impact on the faecal digestibility of the crude protein, NDF and energy content of the whole diet (P<0.001) and on the ileal protein digestibility, especially with 300 g AFs kg⁻¹ diet. The level of AFs in the diet had no effect on stomach weight (P>0.05) but increased the weight of the rest of the gastrointestinal tract (P<0.001). The rate of AF fibre fermentation in the pig large intestine was measured using an in vitro gas test. The rates were much lower than tropical tree foliage, which can also be used in pig diets in the tropics. This could partly explain the low apparent digestibility of AFs in pigs. In conclusion, the inclusion level of AFs in rations for sows should be limited to 150 g AFs kg⁻¹ diet due to the low digestibility and energy density, as well as the negative impact on the digestibility of the whole diet.     

Zinc incorporation in the otoliths of juvenile pink snapper (Pagrus auratus Forster): The influence of dietary versus waterborne sources

Separate laboratory experiments were conducted to examine if incorporation of Zn into the otoliths of juvenile pink snapper (Pagrus auratus Forster) was related to levels in the food and/or water. In the first experiment, fish were fed a regular diet (600 mg Zn kg^− 1 dw, control group) or a Zn-enriched diet (6000 mg Zn kg^− 1 dw or 9000 mg Zn kg^− 1 dw) for 35 days. In the second experiment, fish were exposed to waterborne Zn concentrations of < 0.005 µg L^− 1 (control), 50 µg L^− 1, 100 µg L^− 1 and 200 µg L^− 1 for 35 days. The sagittal otoliths were analysed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Juvenile fish exposed to higher concentrations of waterborne Zn did not display increased Zn levels in their otoliths. However, Zn levels in the otoliths of fish consuming the Zn-enriched diet were significantly higher relative to control fish. This study clearly demonstrated that dietary Zn was the major source of Zn incorporated into the otoliths by this marine fish.     

Termiticidal activity of lectins from Myracrodruon urundeuva against Nasutitermes corniger and its mechanisms

The isolation of lectins from Myracrodruon urundeuva bark (MuBL) and heartwood (MuHL) as well as the termiticidal activity of MuHL against Nasutitermes corniger has already been described. This work reports on the purification of a leaf lectin (MuLL) and the characterization of MuBL, MuHL, and MuLL; also described are the resistance of hemagglutinating activity of the three lectins to trypsin activity from N. corniger gut and the termiticidal activity on N. corniger of MuBL (LC₅₀ of 0.974 mg ml⁻¹ on workers and 0.787 mg ml⁻¹ on soldiers) and MuLL (LC₅₀ of 0.374 mg ml⁻¹ on workers and 0.432 mg ml⁻¹ on soldiers). The antibacterial effect of MuBL, MuHL, and MuLL on bacteria from gut of N. corniger was also investigated and lectins showed similar bacteriostatic activity (MIC of 62.5 ??g ml⁻¹ for workers and 125 ??g ml⁻¹ for soldiers). MuBL and MuHL were more efficient bactericidal agents on bacteria in the workers’ gut (MBC of 125 ??g ml⁻¹) than MuLL (MBC of 250 ??g ml⁻¹) and similar bactericidal activity was detected on bacteria in the gut of soldiers (MBC of 250 ??g ml⁻¹). The termiticidal activity of M. urundeuva lectins can be explained by the chitin-binding property, resistance to termite digestive enzyme, and the antibacterial effect on symbiotic bacteria of N. corniger gut.     

The use of warmed water treatment to induce protective immunity against the bacterial cold-water disease pathogen Flavobacterium psychrophilum in ayu (Plecoglossus altivelis)

We investigated the induction of protective immunity against bacterial cold-water disease (BCWD) caused by Flavobacterium psychrophilum by warmed water treatment in ayu (Plecoglossus altivelis). Fish were immersed in a live bacterial suspension (10⁷ CFU mL⁻¹) for 30 min and placed in 700 L concrete tanks. The 28 °C warmed water treatment lasted 3 days and began 1, 6, and 24 h after immersion in the live bacterial suspension. A naïve control fish group was immersed in a sterilized modified Cytophaga (MCY) broth instead of the bacterial suspension. Fourteen days after the immersion, agglutination antibody titers against F. psychrophilum were measured by using micro-titer methods. Fish were then exposed to a bacterial bath to infect them with live F. psychrophilum, and cumulative mortality was monitored. Fish treated with warmed water at 1, 6, and 24 h after immersion in the live bacterial suspension had cumulative mortalities of 36%, 30%, and 18%, respectively, all of which were significantly lower than the cumulative mortality of the naïve control fish (90%). Treated fish also showed high antibody titers against F. psychrophilum in agglutination tests. These results demonstrate that warmed water treatment could not only cure BCWD but also immunize the fish against the causative agent F. psychrophilum.     

The effect of fucoidan from brown seaweed Sargassum wightii on WSSV resistance and immune activity in shrimp Penaeus monodon (Fab)

The polysaccharide-fucoidan was extracted from brown seaweed Sargassum wightii and characterized through FT-IR and ¹³C & ¹H NMR analysis. The extracted fucoidan was supplemented with pellet diets at three different concentrations (0.1, 0.2 and 0.3%). The fucoidan supplemented diets were fed to Penaeus monodon for 45 days, then challenged with WSSV and the mortality percentage was recorded daily up to 21 days. During the challenge test, the control group showed 100% mortality within 10 days, but in the experimental groups, the mortality percentage (51-72% within 21 days) was decreased considerably (P < 0.05) with respect to the concentrations of fucoidan. The reduction in mortality percentage of experimental groups over control group was ranged from 50.81 to 68.06%. During challenge experiment, the immunological parameters such as THC, prophenoloxidase activity, respiratory burst activity, superoxide dismutase activity and phagocytic activity were measured before injection of WSSV (0 day) and after the injection of WSSV on 10th and 21st days, respectively. All the immunological parameters of experimental groups were significantly (P < 0.05) increased than control group. RT-PCR analysis confirmed the considerable reduction of WSSV DNA copy numbers with respect to the concentration of fucoidan. It was concluded that P. monodon fed with fucoidan of S. wightii supplemented diet had enhanced the innate immunity and increased resistance against WSSV infection.     

Effects of the dietary administration of sodium alginate on the immune responses and disease resistance of Taiwan abalone,Haliotis diversicolor supertexta

Sodium alginate extracted from brown algae was reported to enhance the immune response and resistance of fish and shrimp. In this study, survival rates of the abalone, Haliotis diversicolor supertexta, against Vibrio parahaemolyticus, and its non-specific immune parameters such as the total haemocyte count (THC), phenoloxidase (PO) activity, respiratory bursts, superoxide dismutase (SOD) activity, phagocytic activity, and clearance efficiency to V. parahaemolyticus by H. diversicolor supertexta were determined when abalone (4.5 ± 0.4 g) were fed diets containing sodium alginate at 0, 1.0, 2.0, and 3.0 g kg^?1. Abalone fed a diet containing sodium alginate at 2.0 and 3.0 g kg^?1 for 14 days and at 1.0 g kg^?1 for 21 days had significantly higher survival rates than those fed the control diet after challenge with V. parahaemolyticus. The relative survival percentages of abalone fed the 1.0, 2.0, and 3.0 g kg^?1 sodium alginate-containing diets for 14 and 21 days were 16.1%, 40.0%, and 48.0%, and 63.6%, 27.3% and 22.6%, respectively. The PO activity, respiratory bursts, SOD activity, and phagocytic activity and clearance efficiency of V. parahaemolyticus of abalone fed the sodium alginate-containing diets at 1.0, 2.0, and 3.0 g kg^?1 were significantly higher than those of abalone fed the control diet for 14 days. After 21 days, the PO activity, respiratory bursts, SOD activity, and phagocytic activity and clearance efficiency of V. parahaemolyticus by abalone fed the sodium alginate-containing diet at 1.0 g kg^?1 were significantly higher than those of abalone fed the other diets. It was concluded that sodium alginate can be used as an immunostimulant for abalone through dietary administration to enhance immune responses of abalone and resistance against V. parahaemolyticus, which were related to the dose and timing of administration.     

Enhanced Aeromonas salmonicida bacterin uptake and side effects caused by low frequency sonophoresis in rainbow trout (Oncorhynchus mykiss)

Low frequency sonophoresis (LFS) has been recognized as one of the most advanced technologies in transdermal delivery of substances, due to the modification of the stratum corneum lipid bilayer, in focal skin applications in mammals. Based on these findings, LFS has been suggested as a potential technology to be used for enhancement in immersion fish vaccination. In contrast to mammals where LFS is applied to discrete regions of the skin, in fish the whole individual needs to be exposed for practical purposes. The current study evaluated the impact of LFS at 37 kHz on the uptake of an Aeromonas salmonicida bacterin and side effects of the treatment in rainbow trout. Quantitative real time PCR (qPCR) and immunohistochemistry were used to examine the bacterin uptake into skin and gill tissue. Side effects were assessed by behavioural examination, histology and blood serum analysis. The sonication intensity of 171 mW/cm² was enough for increasing skin permeability, but caused heavy erratic swimming and gill haemorrhages. Sonication intensities as low as 105 mW/cm² did not modify skin permeability and enhanced the bacterin uptake into the gill tissue by factor 15 compared to conventional immersion. Following sonication, the gill permeability for the bacterin decreased after 20 min and 120 min by factor 3 and 2, respectively. However, during sonication, erratic swimming of the fish raised some concerns. Further reduction of the sonication intensity to 57 mW/cm² did not induce erratic swimming, and the bacterin uptake into the gill tissue was still increased by factor 3. In addition, a decreasing albumin–globulin ratio in the serum of the rainbow trout within 40 min revealed that LFS leads to an inflammatory response. Consequently, based on both increased bacterin uptake and the inflammatory response, low intensity LFS has the potential to enhance vaccine immunity without significant side effects.     

Actinoplanes utahensis ZJB-08196 fed-batch fermentation at elevated osmolality for enhancing acarbose production

Acarbose, a potent α-glucosidase inhibitor, is as an oral anti-diabetic drug for treatment of the type two, noninsulin-dependent diabetes. Actinoplanes utahensis ZJB-08196, an osmosis-resistant actinomycete, had a broad osmolality optimum between 309 mOsm kg⁻¹ and 719 mOsm kg⁻¹. Utilizing this unique feature, an fed-batch culture process under preferential osmolality was constructed through intermittently feeding broths with feed medium consisting of 14.0 g l⁻¹ maltose, 6.0 g l⁻¹ glucose and 9.0 g l⁻¹ soybean meal, at 48 h, 72 h, 96 h and 120 h. This intermittent fed-batch culture produced a peak acarbose titer of 4878 mg l⁻¹, increased by 15.9% over the batch culture.     

Occurrence of Flavobacterium psychrophilum in fish-farming environments

Occurrence of Flavobacterium psychrophilum in fish farms and fish-farming environments was studied using agar plate cultivation, the immunoflourescence antibody technique (IFAT) and nested PCR. Characteristics of 64 F. psychrophilum isolates from rainbow trout Oncorhynchus mykiss, fish farm rearing water, ovarian fluid and wild fish were serotyped, ribotyped and compared biochemically. Virulence of F. psychrophilum isolates from different sources was compared by injection into rainbow trout. Additionally, the number of F. psychrophilum cells shed by naturally infected rainbow trout was determined. F. psychrophilum was detected and isolated from skin mucus, skin lesions and internal organs of diseased rainbow trout and from fish without clinical disease. The pathogen was also present in wild perch Perca fluviatilis, roach Rutilus rutilus, and ovarian fluids of farmed rainbow trout brood fish. Isolates were biochemically homogenous, excluding the capability to degrade elastin. Five different agglutination patterns with different antisera against F. psychrophilum were found among the isolates studied. Although several different ribopatterns were found (ClaI: 12 ribopatterns and HaeIII: 9 ribopatterns), ribotype A was the most dominant. Farmed rainbow trout brood fish carried a broad-spectrum of serologically and genetically different F. psychrophilum in ovarian fluids. Virulence of the tested isolates in rainbow trout varied and naturally infected rainbow trout shed 10(4) to 10(8) cells fish(-1) h(-1) of F. psychrophilum into the surrounding water.     

Immune enhancement in rainbow trout (Oncorhynchus mykiss) by potential probiotic bacteria (Lactobacillus rhamnosus)

The present study assessed the immune enhancement of fish by a lactic acid bacterium (LAB) Lactobacillus rhamnosus (ATCC 53103). The bacterium was administered orally at five different doses 7.9 x 10(4) (LAB4), 2.1 x 10(6) (LAB6), 2.8 x 10(8) (LAB8), 1.9 x 10(10) (LAB10) and 9.7 x 10(10) (LAB11) CFU/g feed to rainbow trout for two weeks and the feed was changed to un-supplemented diet. From the onset of feeding supplemented diets at 1, 2, 3 and 4 weeks, blood and mucus samples were taken. During the LAB feeding period L. rhamnosus persisted in the fish intestine and in the tank water in high numbers. However, L. rhamnosus disappeared from the intestine, skin mucus and tank water within one week after the change to the non-supplemented feed. In comparison to untreated control fish, respiratory burst activity of blood cells was raised significantly in the LAB4 treated group on week 2. Serum-mediated killing of Escherichia coli was increased significantly in group LAB6 on week 2. Serum immunoglobulin levels were significantly raised only in LAB8 group on week 1 and in LAB4 and LAB8 at the end of the trial. The results show that rainbow trout immune parameters were enhanced by using probiotic bacteria.     

Effect of diets containing sesame oil on growth and fatty acid composition of rainbow trout (Oncorhynchus mykiss)

The aim of this study was to investigate effects of fish oil replacement by sesame oil in combination with other vegetable oils in diets with regard to growth performance, feed utilization, desaturation and elongation, whole fish and liver fatty acid profiles of juvenile rainbow trout. Sesame oil (SO) used in the feeds was a mixture of linseed (LO), sunflower (SFO) and fish oil (FO), whereas the control diet contained only FO. Duplicate groups of 60 rainbow trout (~7 g) held under similar culture conditions were fed 2% of their body weight per day for 75 days. At the end of feeding trials, there was no difference in feed utilization efficiency or growth performance between the control group and the groups with added sesame oil (P > 0.05). However, viscerosomatic and hepatosomatic index values were significantly higher (P < 0.05) in fish fed with FO30/SO35/SFO35 diets. Results showed that total body lipid levels of fish fed diets containing sunflower oil were higher than in the other experimental groups (P < 0.05). However, crude lipid levels were similar in fish fed the control diet and the diet with sesame oil (FO30/LO35/SO35), which is sunflower oil‐free. Crude lipid levels of fish livers were not influenced by the diets (P > 0.05). Diets with sesame oil increased desaturation and elongation of 18 : 3n‐3 towards n‐3 HUFA. The conclusion was that the diet addition of sesame oil in combination with other vegetable oils increased the nutritional quality of the whole fish and liver of juvenile rainbow trout, in particular the docosahexaenoic acid (DHA) level. Therefore, sesame oil may be of interest for use in aquaculture.     

Skin mucus protease from rainbow trout, Salmo gairdneri Richardson, and its biological significance

The skin mucus of rainbow trout, salmon, charr, cod, coalfish, plaice and redfish contain, besides lysozyme and haemagglutinins, protease activity. The mucus protease from rainbow trout has been purified, characterized and shown to be indistinguishable from the trypsin produced in pylorus caecae. This enzyme activity can escape detection in mucus since it is inhibited by serum components which may contaminate the skin mucus as a result of stress and handling of the fish prior to collecting the mucus.     

Immunomodulatory effects of decaffeinated green tea (Camellia sinensis) on the immune system of rainbow trout (Oncorhynchus mykiss)

In order to study the immunomodulatory effects of decaffeinated green tea extract on rainbow trout, a study with a 30-day feeding trial was conducted. Commercial diets with graded levels of decaffeinated green tea extract, 20 mg (T1), 100 mg (T2), 500 mg (T3) per kg feed were prepared. 120 rainbow trout (35 ± 3 g) were randomly assigned to 4 groups in triplicates and fed one of the 3 experimental diets formulated or control diet. After feeding trial, 12 fish from each group were sampled for analysis of some immunological parameters. Remaining fish were injected with 0.5 ml of chicken red blood cell (C-RBC) suspension (2%) intraperitoneally on days 5 and 15 after feeding trial. Results of the current study showed that the inclusion of 20 mg kg-1 green tea (T1) in fish diet enhanced the serum bactericidal activity against Yersinia ruckeri, while significant elevation of lysozyme activity was shown in T2 group. Anti-trypsin activity due to α1-antiprotease was significantly higher in T1 and T2 groups while peroxidase content showed significant increase in all treatment groups compared to control group. Hemagglutination antibody titer against C-RBC was significantly higher in fish administered with 100 mg kg(-1) green tea (T2). Our findings showed that decaffeinated green tea in lower doses of administration could be optimum to enhance the immunity of rainbow trout.     

Susceptibility of rainbow trout Oncorhynchus mykiss,Atlantic salmon Salmo salar and coho salmon Oncorhynchus kisutch to experimental infection with sea lice Lepeophtheirus salmonis

Physiological, immunological and biochemical parameters of blood and mucus, as well as skin histology, were compared in 3 salmonid species (rainbow trout Oncorhynchus mykiss, Atlantic salmon Salmo salar and coho salmon O. kisutch) following experimental infection with sea lice Lepeophtheirus salmonis. The 3 salmonid species were cohabited in order to standardize initial infection conditions. Lice density was significantly reduced on coho salmon within 7 to 14 d, while lice persisted in higher numbers on rainbow trout and Atlantic salmon. Lice matured more slowly on coho salmon than on the other 2 species, and maturation was slightly slower on rainbow trout than on Atlantic salmon. Head kidney macrophages from infected Atlantic salmon had diminished respiratory burst and phagocytic capacity at 14 and 21 d post-infection (dpi), while infected rainbow trout macrophages had reduced respiratory burst and phagocytic capacities at 21 dpi, compared to controls. The slower development of lice, coupled with delayed suppression of immune parameters, suggests that rainbow trout are slightly more resistant to lice than Atlantic salmon. Infected rainbow trout and Atlantic salmon showed increases in mucus lysozyme activities at 1 dpi, which decreased over the rest of the study. Mucus lysozyme activities of infected rainbow trout, however, remained higher than controls over the entire period. Coho salmon lysozyme activities did not increase in infected fish until 21 dpi. Mucus alkaline phosphatase levels were also higher in infected Atlantic salmon compared to controls at 3 and 21 dpi. Low molecular weight (LMW) proteases increased in infected rainbow trout and Atlantic salmon between 14 and 21 dpi. Histological analysis of the outer epithelium revealed mucus cell hypertrophy in rainbow trout and Atlantic salmon following infection. Plasma cortisol, glucose, electrolyte and protein concentrations and hematocrit all remained within physiological limits for each species, with no differences occurring between infected and control fish. Our results demonstrate that significant differences in mucus biochemistry and numbers of L. salmonis occur between these species.