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.