BACKGROUND: Numerous studies have investigated the positive effect of chitosan and nano-chitosan loaded clinoptilolite on growth performance, digestive enzyme activity, and intestinal histomorphology in different fish species. However, there are no data evaluating the potential effect of the composites on the fish stomach.OBJECTIVES: In the current study, the effects of chitosan and nano-chitosan loaded clinoptilolite on histological features and pepsin activity in the rainbow trout stomach were considered.METHODS: Chitosan and nano-chitosan loaded clinoptilolite were synthesized, and then two hundred and forty fish (~27.75 g) fish were distributed in eight groups each in three replicates. Ten days after adaptation, the fish were fed with eight diets, including control diet (CTR), clinpotilolite (T1), chitosan composites (T2, T3, T4), and nano-chitosan composites (T5, T6, T7) for 70 days. Afterward, all fish in each tank were anesthetized in clove extract (50 μl/l), and tissue samples were obtained for pepsin activity (n= 5) and histological assay (n = 5).RESULTS: The groups administrated with nanochitosan composites showed the highest pepsin activity (P˂0.05). Additionally, histological examinations exhibited a higher epithelial height, increased mucosal density, and oxynticopeptic cells hypertrophy in fish fed composites compared to the CTR group (P˂0.05). Meanwhile, nanochitosan composite administration could cause higher reaction of secreted granules to periodic acid–Schiff (PAS) staining.CONCLUSIONS: The findings demonstrated the potential application of chitosan and nano-chitosan loaded clinoptilolite composites for improvements in the histomorphology and pepsin activity of the rainbow trout stomach, resulting in higher growth performance.

BACKGROUND: Intensive aquaculture and commercialization production are believed to be needed for improving fish health status and probiotics are candidates to achieve this goal. OBJECTIVES: In this study, we utilized Lactobacillus plantarum and Lactobacillus pentosus as autochthonous food supplementation for biochemical investigation in rainbow trout. METHODS: In the current study, 240 juvenile rainbow trout with an average weight of 15 ± 2 g were randomly divided into four groups with three replications. Group 1, 2, and 3 were fed with 108 CFU/g of L. plantarum, L. pentosus, and the combination of these two probiotics, respectively. The control group was fed with the normal diet, for 60 days (2 % of body weight, 3times per day). Samples were taken at days 0 and 60 and biochemical parameters and hepatic enzymes activity were then investigated. RESULTS: Most biochemical factors had positive changes in the fish fed with probiotics, particularly in L. plantarum group (p < 0.05). Furthermore, the results exhibited a significant decrease in ALP level in the probiotic groups, particularly in L. pentosus group (p < 0.05). Meanwhile, AST enzyme activity in plantarum+pentosus group was higher than that in the other groups (p < 0.05). CONCLUSIONS: The present results indicated the effectiveness of food supplementation with probiotics in fish diet with the preference of probiotic to improve the biochemical factors and hepatic enzymes activity of rainbow trout, Oncorhynchus mykiss.

BACKGROUND: The use of natural immune stimulants is one of the most effective methods for strengthening immunity and preventing diseases in fish. OBJECTIVES: Due to the abundance of red algae (Laurencia caspica) in the Caspian Sea, the aim of this study was to investigate the effect of this algae on growth performance and blood indices of rainbow trout. METHODS: The present study was performed on 750 randomly selected rainbow trout (Oncorhynchus mykiss) in 5 experimental treatments including an algal extract-free diet (control), and diets supplemented with 0.5, 1, 1.5, and 2% of algal hydroalcoholic extract. During the experimental period, fish were sampled to measure growth performance and blood indices every two week for 8 weeks. RESULTS: Growth indices were not affected by the algal extract at the end of eight weeks of feeding. There were no significant differences in fish survival at different treatments. Total counts of red blood cells, white blood cells, hematocrit percentage, hemoglobin concentration and neutrophil and monocyte percentages were affected by algal extract with significant increases compared to the control group (p < /em><0.05). Results of serum biochemistry showed that significantly increased total protein, albumin and globulin and also significantly reduced ALT, AST and ALP compared to the control in rainbow trout. CONCLUSIONS: Based on the results of this study oral use of red algae (L. caspica) as an immune stimulant in rainbow trout (O. mykiss) was recommended.

BACKGROUND: The sources of fish oil for use in aquaculture is limited and different oil sources vary in fatty acid composition. OBJECTIVES: The main objective of this experiment was to determine the effects of plant oil sources such as soybean and canola oils with or without L-carnitine supplement on some blood biochemical parameters and growth performance of fingerlings rainbow trout. METHODS: In 3×2 factorial experimental design, 180 rainbow trout with 28±2 g initial body weight were randomly divided into six groups with three replicates and fed two times a day at ad libitum by dietary treatments during 10 weeks. The experimental diets contained three dietary oil sources such as fish, soybean and canola oil; and two supplemental dietaries L- carnitine levels (0 and 1 g.kg-1). Feed conversion ratio, specific growth rate, feed intake, body weight gain and blood biochemical parameters of fish such as albumin, total protein, triglyceride, cholesterol and high-density lipoprotein (HDL) were measured at the end of the experiment. RESULTS: Replacement of fish oil by soybean and canola oil had no significant effect on growth performance such as body weight gain, feed intake, feed conversion ratio, specific growth rate, hepatosomatic index, carcass weight and condition factor of fish. L-carnitine supplement significantly improved weight gain and feed conversion ratio and increased condition factor of fish (P<0.05). Soybean oil significantly increased cholesterol and triglyceride level, and canola oil decreased HDL and globulin level in blood serum of fish (P<0.05). CONCLUSIONS: Results of this study showed that fish oil could be wholly replaced by soybean or canola oil in the diet of rainbow trout and also physiological responses and growth performance of fish to carnitine supplement were affected by dietary oil sources.

BACKGROUND: Today the use of natural substances plays a major role in improving the growth and immunity of aquatic organisms. OBJECTIVES: The purpose of the present study was to evaluate the effects of Iron nanoparticles with Lactobacillus casei as a probiotic on growth parameters and probiotic counts in rainbow trout intestine. METHODS: Seven hundred and twenty fish with 12±0.49 g initial weight were prepared and after acclimatized to the laboratory conditions divided randomly into six groups. First group was selected as control, other groups were fed with a commercial diet supplemented with 108 CFU/g Lactobacillus casei (group 2), 50 µg/kg Iron nanoparticles (group 3), 100 µg/kg Iron nanoparticles (group 4), 50 µg/kg Iron nanoparticles with 108 CFU/g Lactobacillus casei (group 5) and 100 µg/kg Iron nanoparticles with 108 CFU/g Lactobacillus casei (group 6), respectively. Biometry and intestine bacteriologic examination were carried out at days 0 and 60. RESULTS: Results showed that growth parameters (weight gain, body weight gain, specific growth rate, daily growth rate, and condition factor and food conversion rate) were significantly higher in group 5 compared with the other groups. Also, intestine bacterial counts increased by using Iron nanoparticles in combination with Lactobacillus casei. The fish that received 100 µg/kg Iron nanoparticles and probiotic had significantly higher bacterial counts in their intestine compared with the other groups. CONCLUSSIONS: Based on the obtained results we conclude that diet supplementation with Iron nanoparticles and Lactobacillus casei as a probiotic could significantly improve growth parameters in rainbow trout. However, these results would warrant further study on the clinical application of these agents.

BACKGROUND: Replenishing fish oil with vegetable oils and using dietary supplements plays an important role in the metabolism of fats in aquatic animals. Corn oil is one of the vegetable oils that can be a good alternative to fish oil. OBJECTIVES: The aim of this study was to investigate the effects of replacing fish oil with corn oil and the use of dietary supplements L-carnitine and betaine on the metabolism of fats and blood indices of rainbow trout. METHODS: 450 rainbow trout (9.12±0.26 g) were divided into four treatments (three replicates) and were fed with manual diet containing fish oil (1st treatment), corn oil (2nd treatment), fish oil with 500 mg/kg of food containing L-carnitine and betaine (3rd treatment) and corn oil with 500 mg/kg of food containing L-carnitine and betaine (4th treatment) for eight weeks. At the end of study, fatty acid profiles of the treatments were determined by gas chromatography (GC) and blood indices and their weights were also examined. RESULTS: At the end of the experiment, the weight index did not show a significant difference. In the replacement of fish oil with corn oil, the levels of PUFA n-3, C18:3n3, C20:3n3, C20:5n3 and C22:6n3 fatty acids significantly decreased in fish carcasses and the PUFA n-6, C18:2n6, C20:2n6 and C20:4n6 increased significantly, but no significant difference was observed in total SFA and MUFA fatty acids. L-carnitine and betaine increased the EPA accumulation in fish oil and corn oil significantly, and the number of white blood cells in corn oil, L-carnitine and betaine fed fish (fourth treatment) were increased compared to fish oil treatment (first treatment), significantly (p < /em><0.05). CONCLUSIONS: Considering the effect of corn oil, L-carnitine and betaine supplements on increasing the n-6 PUFA fatty acids, essential EPA and white blood cell counts, the use of corn oil and L-carnitine and betaine supplements in rainbow trout diet is recommended.

BACKGROUND: Replacement of natural materials with syntheticdrugs in order to increase production and safety. OBJECTIVE: The purposeof this study was to investigate the effect of feed supplemented with ginger (Zingiberofficinale) extract on the growth, biochemical and hemato-immunologicalparameters of rainbow trout (Oncorhynchus mykiss). METHODS: Fishwith an average body weight 14.1±0.2 g were fed diet for 8 weeks with 0.5% and1% ginger extract and with unsupplemented commercial diet as the control. Bloodsamples were collected from caudal vein from apparently healthy fish at the endof trial. Growth (weight gain, specific growth ratio and condition factor),hematological (RBC,WBC, Hb, Hct, monocyte, lymphocyte and neutrophil),Biochemical (glucose, total protein, triglycerides, cholesterol, albumin, AST,ALT, LDH and ALP) and immunological (lysozym activity, ACH50,IgM, and SOD)parameters were determined. RESULTS: The results showed that there wereno significant differences (p>0.05) in growth, hematological, biochemicaland metabolic enzymes between fish fed control and ginger extractsupplementation. The lowest level of cortisol was observed in 0.5% gingerextract (p<0.05). Lysozyme activity was significantly increased in 0.5%ginger extract fed fish (p<0.05). CONCLUSIONS: The results suggestthat by using 0.5% ginger extract there will be an improvement in growth andimmune function of rainbow trout

BACKGROUND: Nowadays essential oils with antioxidant properties are used in order to increase the shelf life of pre-cooked food. Objectives: This study was carried out to compare the effect of Cumin and three methods of cooking, frying, oven baking and steaming on oxidative changes of pre-cooked fillet of rainbow trout. Chemical (DPPH(1,1- Diphenyl- 2- picryl hydrazine) for Cumin and FFA (Free Fatty Acid), PV(Peroxide value), TBARS) ، Thiobarbituric acid reactive substances) and sensory indicators, were evaluated during  4 months storage at freezing temperatures. Methods: Fillet samples were treated with Cuminum cyminum EOs and BHT. The study was based on application of cooking methods, frying at 180° C for 4 min in sunflower oil, baked in the oven at 200 °C for 22 min and steamed at 200 °C for 22 min and oxidative changes were evaluated during the period of storage as frozen fillets. Results: The FFA formation showed increase in all groups, oven baked rainbow trout fillets gave the highest increase (P<0.05). The highest value of PV was obtained from fried fillets treated with C. cyminum EOs (4.92  ± 0.23 meq/kg). The TBARS values were not significantly different with fresh-raw fillet after cooking (P>0.05), but the treated samples with EOs generally showed slower oxidative changes than those of the untreated samples. Based on the sensory evaluation, fillet fried was found as a preferred cooking method and also, the additions of C. cyminum EOs have positive effect on sensory quality of baked rainbow trout. Conclusions: Differences in cooking methods includin frying, oven baking and steaming showed that rainbow trout fillet treated with C. cyminum EOs under the frying method are more desirable in terms of chemical changes and sensory analysis compared with the other treatments.

BACKGROUND: It is necessary to potentiate the immune system of fishes against stresses in farms. OBJECTIVES: This study was carried out to address the potential effect of Levamisole on immune system of rainbow trout against density stress. METHODS: 1500 fish (average weight of 50 g) were divided into 5 test groups, in which each test group was repeated three times with average density of 33 kg/m3. They were fed with commercial diet supplemented with Levamisole at concentrations of 0 (control), 100, 250, 500 and 1000 mg / kg for a period of 45 days. The fishes of all groups were then fed with Levamisole free diet and exposed to 2 and 3-fold density stress for the following 15 days. Blood samples were collected on days 0, 15, 30, 45 and 60 to evaluate the serum compliment and lysozyme activity as well as total immunoglobulins. RESULTS: The results showed that all used concentrations of Levamisole just had significant effect on compliment activity after 45 days feeding period (p<0.05). Higher levels of lysozyme and complement activity as well as total immunoglobulin were observed in 1000 mg/kg Levamisole treated group when exposed to density stresses 2 and 3-fold at the end of trial (day 60) (p<0.05). The highest overall survival was found in group which was treated with 1000 mg/kg of Levamisole. CONCLUSIONS: Our results revealed that using 0/1% Levamisole as an immunostimulator in commercial diet could potentiate rainbow trout against outbreak of high density stresses and increase its overall survival.

BACKGROUND: Strepotococcosis caused by Streptococcus iniae is one of the important emerging bacterial diseases in aquaculture sector worldwide. ObjectiveS: In this study, the genetic diversity of S. iniae strains was assessed in some rainbow trout farms in Iran. Methods: Gram positive and catalase negative bacterial isolates were first obtained from 100 trout fish farms in 8 states using routine bacteriological and molecular (PCR) works. The genetic diversity of these bacterial isolates was then assessed using restriction fragment length polymorphism (RFLP) method. Results: Seventy-seven strains of Gram positive and catalase negative cocci were isolated from diseased trout. PCR analysis resulted in identification of 27 strains as S. iniae. RFLP analysis of these strains using 9 digestive enzymes resulted in production of 29 bands with different molecular weight (62-940bp).  Phylogenetic relationship of these strains grouped them in two distinct clusters. Twenty-six strains from Tehran, Mazandaran, Gilan, Lorstan, Fars and Charmaha-va-Bakhtiary provinces showed high homogeneous similarity above 99%, while one strain from Mazandaran province showed some differences with other strains. ConclusionS: S. iniae isolates in trout aquaculture in Iran possess  low genetic diversity.