BACKGROUND: Carnitine biosynthesis needs methionine and lysine amino acids, vitamins niacin and ascorbic acid. So the usage of both L-carnitine and vitamin C may  improve the effects of only L-carnitine. OBJECTIVES: This study was carried out to investigate the effects of different levels of L-carnitine and vitamin C on the growth performance‚ body composition; blood serum parameters in Rainbow trout (Oncorhynchus mykiss) were investigated. METHODS: For this purpose, 540 fingerlings with the average weight 40±2 g were arranged in treatments including 3 vitamin C levels: zero, 500, 1000 and 2 L-carnitine levels: zero, 800 (mg/kg diet), with 3 replicates. RESULTS: Results showed weight gain, special growth rate and feed conversion ratio in the level of 500/800 vitamin C/L-carnitine had a significant increase compared to control (p<0.05). The highest and the lowest lipid content were observed in control and 1000/800vitamin C/ L-carnitine, respectively (p<0.05). The highest protein content was observed in 500/800 vitamin C/L-carnitine (p<0.05). Cholesterol and glucose showed a significant decrease in 500/800 vitamin C/L-carnitine. It was observed that 1000/800 vitamin C/L-carnitine caused significant decrease in blood triglycerides (p<0.05). CONCLUSIONS: Finally, it was determined that using vitamin C 500 and L-carnitine 800 mg/kg diet caused some improvement in growth performance with no  negative effects on blood parameters.

BACKGROUND: Enhancement of the immune system seems to be the most promising method of preventing fish diseases and increasing growth rate. Objectives: The purpose of the present study was to investigate the influence of dietary administration of Zataria multiflora Boiss and Menthapulegium L extracts on phagocytosis, lysozyme, respiratory burst and total white and red blood cells (WBC/RBC) of rainbow trout (Oncorhynchus mykiss). Methods: Two hundred and ten fish (100±10 g) were used in a completely randomized design with 7 treatment and 3 replicates in a 2 weeks period (from 0 to 14 d). The basal diet supplemented with 0 (control), 20, 50 and 100 mg/kg food Z. multiflora and M.pulegium extracts. At the end of the experiment (after 14 days), samples from kidney and blood of the fish were collected in order to determine WBC/RBC (by neubauer chamber), serum lysozyme activity (by turbid metric assay, phagocytosic (by number of yeast cells phagocytosed method) and respiratory burst activities (by reduction of nitroblue tetrazolium method) of head kidney tissue. Results: The results indicated that the highest ratio of phagocytosis and respiratory burst activity was observed in 50 mg/kg extract concentration of Z. multiflora (p<0.05). The highest WBC lysozyme activities were seen   in 100 mg/ kg extract concentration of Z. multiflora. No significant difference was shown between RBC in treatment groups and control group (p>0.05). The highest ratio of phagocytosis activity was observed in 100 mg/kg extract concentration of M. pulegium (p<0.05). No significant difference was observed between WBC /RBC, lysozyme, respiratory burst means in treatment groups and control group (p>0.05). Conclusions: It can be concluded that 50 and 100 mg/ kg of the methanol Z. multiflora and 100 mg/ kg M. pulegium have positive effects on stimulating of innate immune system in O.mykiss, but the influence of Z. multiflora extract with100 mg/ kg  concentration is  better than  M. pulegium extract.

BACKGROUND: Tobacco (Nicotiana tobaccum) is a plant with piscicidal and fertilizing properties. OBJECTIVES: In this study the effect of different concentrations (0.1, 1, 10 and 100mg/l) of hydro-alcoholic extracts of tobacco has been examined on different tissues of Rainbow trout. METHODS: Samples from liver, kidney and gill of Rainbow trout were stained with hematoxylin and eosin and studied under light microscopy. RESULTS: Various histopathological lesions were observed in the liver of Rainbow trout exposed to different concentrations of tobacco. The results showed that with increase in concentrations of tobacco up to 10 and 100mg/l, bloodshed increased and hepatocytes lost their continuity and showed discontinuity mood. Lamellar aneurysm, bleeding and leukocytes infiltration, clubbing at the end of the lamellae, hyperplasia of secondary lamellar epithelium, epithelial lifting of secondary lamellae and creating an edematous space, lamellar shortening, vacuolation and lamellar fusion were the more abundant branchial lesions after exposure to tobacco. Separating the epithelium from basement membrane, hypertrophy, glomerular capillary dilation and tubular degeneration were observed in renal tissues in all treatments. At higher concentrations of tobacco (10 and 100mg/l), renal tubular necrosis was also observed. According to the results liver of rainbow trout showed a few histopathological alteration following exposure to tobacco extracts. Unlike the liver, gills of rainbow trout due to direct contact with pollutants showed more lesions. CONCLUSIONS: Tobacco extract has more pathological effects on gills in comparison with liver and kidney of Rainbow trout due to direct contact with the dissolved pollutant.

BACKGROUND: Yersiniosis or enteric redmouth disease (ERM), caused by Yersinia ruckeri, is a serious bacterial disease in the farmed salmonids that causes economic problems in this industry. OBJECTIVES: This study was aimed to assess the experimental pathogenicity of Yersinia ruckeri in Rainbow trout (Oncorhynchus mykiss). METHODS: Two hundred Rainbow trout weighting 100-120 g, challenged with different strain of Yersinia ruckeri were obtained from affected trout farms using intra peritoneal injection route at a concentration of 108 cells/ml (0.1 mL per fish) to evaluate the virulence of these isolates. Each treatment group included 10 fish in two replicates and control fish received 0.1 mL sterile normal saline (0.9% NaCl). Following the intra peritoneal challenge, macroscopic and microscopic findings were determined. The most virulent strain was then used to determine the lethal concentration (LD50) using both intra peritoneal and bath method at dilutions of 103-1010 cells/mL. RESULTS: Macroscopically, anorexia, lethargy, circular swimming near the surface, blackening of skin, exophthalmia, hyperemia and hemorrhage in different parts of body, anal prolapse, enlarged liver and spleen were observed. Microscopically, hyperemia of hepatic sinusoids and vessels, necrosis and vacuolization of hepatocytes, increase in the abundance of macrophage centers in kidney, dilatation of Bowman’s space, degeneration and necrosis of kidney tubules, severe necrosis and detachment of intestinal villi, hyperplasia and clubbing of epithelial cells of secondary lamellae, spleen cell necrosis, goblet cell hyperplasia and thickening of epidermis layer in the tongue mucosa were observed.  The LD50 of intra peritoneal injection was calculated 1.2×106cells per fish 48 h post challenge. In bath route, LD50 was obtained 5×108 Cells/ml after 96 h. CONCLUSIONS: The results obtained from this study show virulence diversity of native strains.

BACKGROUND: To reduce adverse environmental effects resulting from repeated use of chemical contaminants, herbal extracts are a natural suitable alternative in aquaculture. Objectives: The present study investigated the effects of Biarum carduchorum and Quercus Infectoria Gall extracts on percentage of hatching and survival rate in the early growth stage of rainbow trout (Oncorhynchus mykiss) larvae compared with malachite green (MG). Methods: To assess the percentage of hatching and survival rate in the early growth stage, B. carduchorum was used at 400 mg/l for 30 minutes per day, Q. Infectoria Gall at 40 mg/l for 30 minutes per day and MG as the positive control at 2 mg/l for 20 minutes per day. Normal control without any treatment was also included. Each treatment trial was provided in three replicates.  Results: The obtained results showed that the mortality level in normal control was significantly higher than other groups in the hatching stage (p<0.05). Also, the mortality rate in eggs treated with B. carduchorum was significantly lower than both MG and Q. Infectoria Gall groups (p<0.05). The mortality rate in eggs treated with Q. Infectoria Gall was significantly higher than MG group (p<0.05). In addition, the mortality rate of the produced larvae was significantly higher in both Q. Infectoria Gall group and normal control groups than the other two groups (p<0.05).Conclusions: The results showed that use of B. carduchorum at 400 mg/L is able to significantly improve the survival rate of rainbow trout eggs and larvae during incubation period. It can be comparable to MG.

Growth indices were examined in 24 identically managed tanks, each containing 120 diploid juvenile rainbow trout (initial mean body weight, 9.3 g), during a 12-week study to examine tank effects associated with tank location in a multi-user research facility. Growth indices included mean body weight, feed intake, feed conversion index, and specific growth rate. The null hypothesis that tank effect had no effect on growth over the 12-week period was rejected (P = 0.038), and mean weight in individual tanks differed by as much as 18.7%. During the study, it was determined that the proximity of tanks to common-use walkways in the facility could affect growth indices. This was indicated by significant differences in the mean fish weights among blocks of tanks served by different header tanks after 4 (P = 0.001) and 8 (P = 0.024) weeks. The block containing tanks of fish with the highest mean weight was nearest to the 2 common-use walkways in the facility. Fish in this block of tanks, compared with those in other blocks, had significantly greater feed intake but no significant differences in conversion efficiency. Compensatory growth, a well known growth attribute in fishes, diminished the difference in mean weight between these blocks of tanks by the end of the study. Comparison of paired tanks within header tank blocks indicated that fish in those located nearest to walkways had higher feeding rates over the 12-week period (P = 0.048), but less efficient teed conversion (P = 0.040) than did fish in matched tanks located farthest from walkways. However, there were no differences in mean weight of fish. Results of this trial document the risks involved in identifying fish in a tank as the experimental unit when treatments are administered to the tank of fish, the latter being the true experimental unit.

Introduction: The goal of this study was to assess the influence of vaccination against enteric redmouth disease on oxidative stress biomarkers and antioxidant defence in the muscle tissue of rainbow trout (Oncorhynchus mykiss Walbaum) vaccinated against Yersinia ruckeri in the first and second month after immunisation. Material and Methods: Healthy fish were vaccinated orally with inactivated whole cells of a virulent strain of Y. ruckeri. One and two months after immunisation the muscle samples were collected. Results: No significant difference was noted in lipid peroxidation level in either the first or second month after vaccination, while aldehydic and ketonic derivatives of oxidatively modified proteins (OMB) in the vaccinated group were significantly lower in the second month compared to those in the first month after vaccination (P < 0.05). The content of ketonic derivatives of OMB in muscles in the first month after immunisation was higher compared to untreated control. All these culminated in a depletion of glutathione peroxidase (GPx) activity and low level of total antioxidant capacity (TAC). Conclusion: Correlations between catalase activity and lipid peroxidation and TAC confirmed the pivotal role of catalase in antioxidant defence during immunisation. From a broader perspective, it is suggested that immunisation of fish with Yersinia vaccine is associated with induced free radical formation and oxidative stress. Free radicals would therefore be at least partially responsible for the induction of both humoral and cellular elements of the immunity and increased protective immunity against Y. ruckeri infection.

The Shewanella putrefaciens group are ubiquitous microorganisms recently isolated from different freshwater fish species and causing serious health disorders. The purpose of the study was to characterise isolates of the S. putrefaciens group with special emphasis on elucidating serological diversity and determining putative virulence factors. Isolates collected from freshwater fish (n = 44) and reference strains were used. The identification of bacteria was carried out using biochemical kits and 16S rRNA sequencing. Polyclonal antibodies were prepared against the S. putrefaciens group. The bacterium’s susceptibility to antimicrobial agents, its enzymatic properties, and its adhesion ability to fish cell lines were also tested. Finally, selected isolates were used in challenge experiments in common carp and rainbow trout. Excluding six isolates undeterminable for species, the bacteria were classified to three species: S. putrefaciens, S. xiamenensis, and S. oneidensis, and showed some phenotypic diversity. Fourteen serological variants of the S. putrefaciens group were determined with the newly developed serotyping scheme. Serodiversity may play an important role in the virulence of particular isolates. Further, S. putrefaciens group members adhere to epithelial cells and produce enzymes which may contribute to their virulence. Challenge tests confirmed the pathogenicity of the S. putrefaciens group for fish.

Introduction: The goal of this study was to assess the influence of vaccination against enteric redmouth disease on oxidative stress biomarkers and antioxidant defence in the muscle tissue of rainbow trout (Oncorhynchus mykiss Walbaum) vaccinated against Yersinia ruckeri in the first and second month after immunisation. Material and Methods: Healthy fish were vaccinated orally with inactivated whole cells of a virulent strain of Y. ruckeri. One and two months after immunisation the muscle samples were collected. Results: No significant difference was noted in lipid peroxidation level in either the first or second month after vaccination, while aldehydic and ketonic derivatives of oxidatively modified proteins (OMB) in the vaccinated group were significantly lower in the second month compared to those in the first month after vaccination (P < 0.05). The content of ketonic derivatives of OMB in muscles in the first month after immunisation was higher compared to untreated control. All these culminated in a depletion of glutathione peroxidase (GPx) activity and low level of total antioxidant capacity (TAC). Conclusion: Correlations between catalase activity and lipid peroxidation and TAC confirmed the pivotal role of catalase in antioxidant defence during immunisation. From a broader perspective, it is suggested that immunisation of fish with Yersinia vaccine is associated with induced free radical formation and oxidative stress. Free radicals would therefore be at least partially responsible for the induction of both humoral and cellular elements of the immunity and increased protective immunity against Y. ruckeri infection.

Based on analysis of available genome sequences, five gene lineages of MHC class I molecules (MHC I-U, -Z, -S, -L and -P) and one gene lineage of MHC class II molecules (MHC II-D) have been identified in Osteichthyes. In the latter lineage, three MHC II molecule sublineages have been identified (MHC II-A, -B and -E). As regards MHC class I molecules in Osteichthyes, it is important to take note of the fact that the lineages U and Z in MHC I genes have been identified in almost all fish species examined so far. Phylogenetic studies into MHC II molecule genes of sublineages A and B suggest that they may be descended from the genes of the sublineage named A/B that have been identified in spotted gar (Lepisosteus oculatus). The sublineage E genes of MHC II molecules, which represent the group of non-polymorphic genes with poor expression in the tissues connected with the immune system, are present in primitive fish, i.e. in paddlefish, sturgeons and spotted gar (Lepisosteus oculatus), as well as in cyprinids (Cyprinidae), Atlantic salmon (Salmo salar), and rainbow trout (Oncorhynchus mykiss). Full elucidation of the details relating to the organisation and functioning of the particular components of the major histocompatibility complex in Osteichthyes can advance the understanding of the evolution of the MHC molecule genes and the immune mechanism.