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Vast application of the antibiotic drugs in animals without due attention  to withdrawal times necessitates quality control of food stuff in terms of antibiotics' residues. Antibiotic residues in food stuff cause bacterial resistance, allergic reactions, toxicity,  carcinogenic effects and change of natural micro flora of intestine in consumers. So, the aim of the present study is detection of antibiotic residues and its contamination rate in cultured rainbow trout.

Four-plate test is one of the microbiological methods of detecting antibiotic  residues  in food stuff, which is based on inhibition zone formation around the sample in four culture media with different pH and test bacteria. For this purpose, 45 samples from skin and meat of rainbow trout fish were obtained randomly from fish market of Tabriz city. After different phases of four-plate test, from a total of 180 skin samples, 13 cases (7.22%) and from a total of 180 meat samples, 18 cases (10%) were diagnosed to be contaminated to antibiotic residues.

The results showed that contamination rate of two tissues, (meat and skin), have no significant difference (P>0.05), and the highest contamination to antibiotic residues  were related to penicillin and macrolides groups (P<0.05).

 

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The aim of this study was to show the effect of four feeding regimes on thyroid hormones concentrations, growth performance and food coefficient in Rainbow Trout applied through 4 treatments and 3 replications in winter 2006. In this research, samples of rainbow trout with an initial mean weight (SO) 47.19±0.42 used in each rearing unite. Fish were fed twice a day ad libitum as follows: Treatment A (TA): which was the control treatment; Continues feeding, Treatment B (TB): 4 weeks of starvation and 5 weeks of re-feeding, Treatment C (TC): 3 weeks of starvation and 5 weeks of re-feeding, and Treatment 0 (TO): 2 weeks of starvation and 5 weeks of re-feeding. Indexes like food coefficient ratio (FCR), specific growth rate (SGR), daily food intake and thyroid hormones (T3, T4) were also examined during the experiment. Blood samples were taken for thyroid hormones concentration at the beginning of the experiment and at the end of the starvation and every 12 days in re-feeding periods. TB and TC had significant difference (P0.05). There were no significant differences between the treatments in FCR (P>0.05). T3 concentration came down

in comparison with the control treatment at the end of the starvation (day 29) (P

in there-feeding periods. T4 concentrations of fasting groups were lower than the control group at the end of fasting periods (P<0.05), but T4 trend in re-feeding periods increased. According to the results, different treatments of feeding regimes could affect the thyroid hormones concentrations. Fasting periods  reduced  and  re-feeding  periods  increased  thyroid  hormones  concentrations.  TB  and  TC showed more indexes of CG in comparison with TA and TO. We concluded that thyroid hormones alone are enough to assess CG and we suggest to use other growth relating physiological elements in different feeding diets and regimes in future studies to complete the evaluation.

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Silkworm pupae meal is a non-conventional animal protein feedstuff. It is the by-product after the silk thread has been wound off from the cocoon. To investigate the effects of animal protein on growth and survival of rainbow trout (Oncorhynchus mykiss), a sixty-day feeding experiment was conducted. Four replacement levels (0, 5, 10 and 15 percent) of silkworm pupae meal were compared using a completely random design. We used 360 juvenile rainbow trout (average weight 55±3.42g) divided into 4 groups and 3 replications, each containing 30 trout for 60 days. Sampling for nutritional effects was carried out every 10 days and at the end of the experiment, weight gain, feed conversion ratio, specific growth rate, protein and efficiency ratio were compared which showed no significant differences (P>0.05) among the treatments. Total length and survival rate were not significantly affected in the treatment groups. The highest percentage of carcass protein and the lowest percentage of carcass fat belonged to the control treatment. Our fmdings showed that silkworm pupae  meal  could replace 15% of fish meal diet in rainbow trout culture.

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A four-week trial was conducted to evaluate the effects of different levels of dietary Betaine on growth, survival and resistance to salinity (35ppt), temperature (24 C), hypoxia and high and low pH stresses in rainbow trout (Oncorhynchus mykiss). Four levels of Betaine as 0 (control), 0.4% (B0.4), 0.8% (B0.8) and 1.2% (B1.2) were used with three replicates. Forty fish (0.67±0.15g) were stocked in each replicate and fed at 4-4.5% of body weight, five times daily. Results showed that there were significant differences in growth, survival, NPU, PER and FCR between B0.4, B1.2 and control diet (P<0.05). Carcass analysis showed that there was higher protein in the carcass of fish fed with diet B0.4 compared to control and B1.2 diet. There were no significant differences in carcass protein content between B0.4 and B0.8. Also, no significant differences were found in carcass crude fat, ash and dry matter among different treatments (P>0.05). Resistances to high and low pH (10.8 & 3.8) and to high temperature (24 C) were significantly better in fish fed with Betaine containing diets compared to the control diet. Resistance to high salinity in B0.4 was significantly better than the control diet and resistance to hypoxia in diet B0.8 was significantly better than the control (P<0.05). The results showed that dietary supplementation of Betaine (0.4%) have positive effects on growth factors, survival, body composition and resistance to environmental stresses in rainbow trout. *Corresponding author

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This research was carried out to determine LC50 for Zataria multiflora essential oil in rainbow trout (Oncorhynchus mykiss) fries at 96 hours. In the process, we used the static O.E.C.D method for 180 rainbow trout fries weighing 5±1 grams in five treatments and one control with three replicates. During the experiments, the mean (±SD) of water temperature was kept at 16±1 C, dissolved oxygen (DO) was 7±0.2mg/l and pH was 8±0.4. We used 5- 25ppm of the essential oil and the results were analyzed using probit analysis procedure. The LC50 96h of Zataria multiflora essential oil was determined as 13.6ppm for rainbow trout (Oncorhynchus mykiss) fry. Based on the results, the useful maximum concentration of Zataria multiflora essential oil was less than 10ppm in rainbow trout fry. The results indicated a narrow therapeutic index for Zataria multiflore essential oil. *Corresponding

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The effects of using different of gammarus meal levels (0, 5, 10 and 20%) instead of kilk fish meal as a protein source on growth performance, feed conversion ratio and survival of rainbow trout (Oncorhynchus mykiss) fingerlings were studied over 8 weeks. Rainbow trout fingerlings (mean body weight 5.48 ± 0.32g) were reared in a completely randomized design with three replications in the same conditions. Based on the results, no significant difference was observed in the final length and weight and specific growth rate among treatments. Increase of gammarus meal in diet led to increase of feed conversion ratio and decrease of survival, but the difference was not significant among treatments. Commercial analysis showed that the cost price of feed increased with increase of gammarus meal in diet, significantly. Thus, results of our study showed that adding up to 10% of gammarus meal instead of kilka fish meal in rainbow trout fingerlings diet is suitable, considering gammarus abundance in the shores of south Caspian Sea and lack of significance in difference on growth, feed conversion ratio and survival. *Corresponding author

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The main objective of this study was to determine the interactive effects of dietary selenium and fat on fatty acid compositions of rainbow trout tissues. We formulated six experimental diets by addition of two fat levels (15 and 30%) and three selenium levels (0.1, 0.15 and 0.2mg/kg) to a basal diet, according to a 3x2 factorial design. Juvenile rainbow trout with initial weights of 6.99g were assigned to 18 tanks with 300L capacity each containing 25 fish, with three replicates for each diet. The result showed that unsaturated fatty acid and tissue oxidation rate increased with an increase in fat content of the diets. Addition of dietary selenium increased enzyme of Glutathione (GSH-Px) activity and at high-fat diet (30% fat), selenium addition improved polyunsaturated fatty acid compositions by depression of oxidation rate. However, inclusion of high dose of selenium (0.2mg/kg) had a negative impact on the Arachidonic and Eicosapentaenoic acids. In conclusion, dietary selenium supplementation can preserve fatty acid quality by controlling fatty acid oxidation at high-fat diet. The results obtained from the current study suggest that rainbow trout at high-fat diet requires 0.15mg/kg selenium to reduce oxidation level. *Corresponding author

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In this study, the effect of gelatin coating enriched with cinnamon oil for fresh fillet of rainbow trout on microbial were studied, chemical and sensory characteristics during storage at refrigerator condition. Fish fillet were treated in gelatin solution (4 percent) containing cinnamon oil and were stored in refrigerator. Total viable count was acceptable (7 log CFU/g) for coated fillets with gelatin coating containing cinnamon essential oil on day 15, but the control fillets also those that were covered with gelatin receipt to 7.88 and 7.44, respectively. In the tenth day. Psychrotrophic count values for the control and gelatin coated fillets significantly were increased more than other treatment. Total volatile bases nitrogen and Thiobarbituric acid values in gelatin with cinnamon coated fillet were less than other treatment. In general, results suggest successful inhibition microbial growth in refrigerated rainbow trout fillet is possible with gelatin incorporated cinnamon coating, as together they kept the sensory characteristics within acceptable limits throughout storage. Gelatin coating together with cinnamon oil provides a type of active coating that can be utilized as a safe preservative for fish under refrigerated storage.

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The main goal of anesthesia in rainbow trout is decrease mobility and reduce stress of fish while breeding, and also facilitate operation such as manipulation to Tagging, Biometry, Sorting, Inspection and Sampling for pathology test. In the present study, Aqueous and alcoholic extract of tobacco plant (Nicotiana tabacum) for Anaesthetizing Rainbow trout (Oncohrynchus mykiss) in 3 weight groups: fry (less than 80 g), growing(about 200 g) and breeding(larger than 1500g) were used. The effective dose of tobacco in treatments 200, 400, 800 and 1600mg/lit in aqueous and 0.7, 1, 1.7 and 3.5mg/lit in alcoholic extract were tested. Totally, we can say that tobacco extract Anaesthetizes the rainbow trout in less than 3 minutes and recovery time is less that 5 minutes. Regarding to anesthetizing time, recovery time and fish relaxing during anesthesia, aqueous extract applies more gentle anesthesia in rainbow trout, and dose 200 to 800 mg/lit of aqueous extract were more successful. Also Regarding to significant correlation between doze and Anesthetics extremity and recovery time (P<0.05), lower dose of tobacco extract can be used to making fish calm for transportation. *Corresponding author

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The aim of the present study was to determine the impact of replacing the fish oil by alternative lipid sources in diets for rainbow trout (Oncorhynchus mykiss) on growth, fatty acid profiles of muscle. Five isonitrogenous and isoenergetic semipurified diets were formulated containing 100% rice bran oil (RBO), 100% linseed oil (LO), 100% Soybean oil (SO) and a 1:1:1:1 rice bran, linseed, soybeen and fish oil mixture (MX) were compared to a pure fish oil (FO) diet. The diets were fed to apparent satiation twice a day to triplicate groups of 30 rainbow trout with an initial weight of 90g for 15 weeks at 12°C.At the end of the experiment, fillet samples were collected from fish for the measurement of fatty acid profile and fillet composition. Fish fed the FO diet had the highest weight gain over the experimental period (280.28 g), However no differences in growth rate and CF were observed across diet groups. Feed conversion ratios (FCR) ranged from 1.12 to 1.24. Significant difference in FCR was found in the group fed an FO diet. The fillet lipid concentrations and fatty acid composition of the fish were significantly affected by the experimental diets. Fish fed the FO diet contained significantly lower lipid levels (20.18%) than those fed the 4 other diets. The highest level of n-3 PUFA concentrations were recorded in fish fed the LO diet (21.8) with significant difference than other diets and the lowest were in those fed the RBO diet (7.84). Fish fed the SO diet contained significantly higher level of n-6 PUFA concentrations (31.72) than other diets and the lowest were in those fed the FO diet (19.15). Fish on the FO diet had a significantly greater percentage of DHA (10.10%) in muscle tissue compared with fish on all other diets and the lowest was in those fed the RBO diet (2.81%). However, the highest level of eicosapentaenoic acid (EPA) concentrations was recorded in fish fed the SO diet (1.84%) and the lowest in those fed the diet (0.67%). This study showed considerable reductions (about 3-fold) in the n-3/n-6 ratio when FO in the fish diet was replaced by rice bran and soybean oils, which may be extremely negative from a nutritional point of view. In other hand linseed oil had the highest n-3/n-6 ratio (0.91) that was comparable with fish oil n- 3/n-6 ratio (0.89). The results in this study imply that an appropriate mix of vegetable oils and FO can replace the sole use of FO in fish feeds.

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In this study, some non-specific immune responses and hematological parameters in rainbow trout juveniles (16g mean weight) and their resistance to Streptococcusis were invetigated following dietary administration of 3 concentrations (0.5, 1, 1.5g/kg of feed) of Echinacea purpurea extract. The non-pecific immune response and hematological parameter compared with control group for 60 days. Evaluated parameters included were of C3, C4, (complement components), superoxide ions (respiratory burst), lysozyme activity, number of WBC, percentage of blood lymphocytes, monocytes and neutrophils. At the end of trial, the relative survival rate (RSR) of fish was evaluated against S. iniae. The results showed that the levels of C3, lysozyme activity, superoxide ions, number of WBC and percentage of neutrophils in the experiment groups (the highest concentration, 1.5g/kg of feed) were increased significantly compared to the control group. Whereas, no significant difference was found in the value of C4 and the percentage of monocytes and lymphocytes in comparison to the control group. The relative survival rates of fish following challenge with Streptococcus iniae, were 91.11 and 44.44 percent in experiment (Echinacea purpurea, concentration of 1.5g/kg of feed) and control group, respectively. In conclusion, the results of the present study demonstrated that Echinacea purpurea. extract enhanced the non-specific immune system and fish resistance against streptococcusis, suggesting that this extract might be used as immunostimulant in fish feed.

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The antibacterial activity of different concentrations of Cuminum cyminum essential oil (0, 0.005, 0.015, 0.045, 0.135, 0.405%) and nisin (0, 0.125, 0.25, 0.75 μg/ml) was explored in lab and food model (fillets of rainbow trout) in controling Streptococcus iniae for 15 days at 8 ºC. The micro-dilution method was used to determine MIC and MBC for nisin and the essential oil, so used for food model. Results showed that MIC and MBC for essential oil and nisin were 0.015, 0.005% and 0.25, 0.125 μg/ml, respectively. For the duration of 15 days no statistical significance was recorded between the different concentrations of nisin and essential oil and control treatment. Results showed that the bacterial growth was delayed in different samples being treated with nisin and essential oil from 3 to 6 days for the given compounds and 6 days for nisin and essential oil in combination. The highest synergistic effect of nisin with essential oil was found in 0.135 and 0.405% concentrations for essential oil and 0.75 μg/ml for nisin at 8 ºC. *Corresponding

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Streptococcusis is the one of the most important bacterial fish diseases with outbreak in rainbow trout farms in Iran. The fish farmers have been largely suffered from huge economic losses due to the Streptococcusis outbreaks in different rainbow trout farms in Iran. The present study assessed the effects of some environmental risk factors on incidence of streptococcusis in rainbow trout farms in Haraz River in Mazandaran Province, Iran. A suit of environmental factors including water temperature, nitrite, nitrate, ammonium, water turbidity, DO, water Debi and total count of bacteria were explored as influential factors. Fish and water samples were randomly collected from 10 farm on a monthly basis throughout a year. Isolation and recognition of strep strains were made using biochemical and PCR tests and the data were analyzed by logistic regression method. According to the results, 20% of the differences were explained by the logistic model. Management of these factors might decline the rate of disease outbreak.

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One of the most important bacterial fish diseases which have caused some outbreaks in rainbow trout farms in Iran is streptococcusis .The farmers have been suffering from huge economical losses due to the disease outbreak in different rainbow trout farms in Iran. The aim of present study was to determine the rate of streptococcusis incidence in different growth stage in the farmed rainbow trout in Haraz River in Mazandaran Province, Iran. Fish specimens along with water samples were collected from 10 haphazardly selected fish farms on a monthly basis throughout a year. After clinical observations, isolation and recognition of strep strains were undertaken using biochemical and PCR tests. The results showed that 4.6% of juvenile fish showed clinical sings of streptococcusis while only 0.7% had strep. contamination. These rates in adult specimens were 8.9 and 1 percent, respectively. The main isolated bacterial strain was Streptococcus uberis

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The genus of saprolegnia is one of the most important pathogenic aquatic fungi in farmed and wild fish. In the present study, fungal infected egss were collected from rainbow trout (Oncorhyncus mykiss) and Caspian trout (Salmo trutta caspius). After purification, 16 isolates were obtained (8 isolates from rainbow trout and 8 isolates from Caspian salmon, respectively). The isolates were then coded as R2 – R9 (rainbow trout) and S2 – S9 (Caspian trout).The registered DNA for S. parasitica (ACTT # 200048) and S. diclina (ACTT # 4206) were used and coded as R1 and S1, respectively. Based on the RAPD profile obtained all samples were divided to 3 groups and members of each group had more than 90% similarity among themselves. According to matrix of similarity and reference strains, the isolates were classified as three groups. Therefore, all of isolates in group 1 and 3 were S. parasitica and S. diclina, respectively, and the members of group 2 were known as Saprolegnia sp. The results of thermal resistance assessment showed that the isolates of rainbow trout and Caspian salmon eggs had slow growth in the temperature between 18 – 20 °C. Thus, R2 and S8 isolates had the lowest radial growth compared to other isolates. The isolates categorized in S. parasitica (group 1) created secoundry zoospores but not observed in two other groups. Thus, catenulated gamme was found in 78% and 55.55% isolates of rainbow trout and Caspian trout eggs, respectively. This study indicated that molecular methods were the best methods for identification of Saprolegnia spp. and it could be applied as a supplementary confirming method.

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A total of 64 specimens of rainbow trout (Onchorhynchus mykiss) from 3 different regions in Iran were collected. About 2-3 g of caudal fin samples were removed from each specimen and preserved in absolute ethyl alcohol and transferred to the genetic laboratory. Genomic DNA was extracted using the phenol-chloroform method and then DNA content and quality was determined using spectrophotometry and agarose gel electrophoresis, respectively. Polymerase Chain Reaction (PCR) of genomic DNA fin samples was carried out using 8 pairs of microsatellite primers. All PCR products were electrophoresed on 6% polyacrylamide gel and stained with silver nitrate. Following the scoring of alleles, all parameters including effective number of alleles, observed and expected heterozygosity, shanon index, Hardy- Weinberg equilibrium test and FST were calculated using AMOVA analysis in the GenAlex and Popgene programs. The results showed that 8 pairs of microsatellite primers were polymorphic. In total, alleles were determined with the range size of 64-280 bp. The locus OtsG 249 had maximum number of allele (9) and loci OtsG 432 and OtsG 474 had minimum number of allele (2). The observed heterozygosity was between 0.869 and 0.916. Hardy- Weinberg departure was observed for most loci from all farms and were disequilibrium. The Fst results showed that maximum FST (0.079) were between farms in Tehran and Yasuj and minimum (0.041) were between farms in Hamadan and Yasuj. Based on the results of AMOVA analysis, significant differences were detected between all farms. The results suggest that the unique genetic variation of rainbow trout in hatchery farms of Iran represents a highly valuable genetic resource and provide useful information for creating a based population in the future breeding programs.

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To evaluate the dietary toxicity of colloidal silver nanoparticles (AgNPs) in rainbow trout, fish were fed with diets containing 0, 20 and 50 mg.kg-1 of AgNPs for 5 weeks and then were fed free nanoparticles diet for a week. During this period, fish growth, as well as silver accumulation and elimination in liver, kidney, gastrointestinal tract and muscle were studied. According to our results, high doses of AgNPs in the fish diet decreased appetite and fish growth. In addition, feeding fish with the diet containing AgNPs (especially at higher doses) increases the accumulation of silver in fish tissues (silver concentration in liver> kidney> gastrointestinal tract > muscle). Although, a oneweek period considered for elimination of nanoparticles from fish tissues were not enough however, caused some changes in the accumulation of silver in different organs of the fish. Observed effects due to fish feeding with diets containing silver nanoparticles, suggests that nanoparticle ingestion could affect the fish health. Therefore, preventing the entry of these new materials into the food chain of aquatic organisms seems to be necessary.

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Rainbow trout, Oncorhynchus mykiss is the most important cold water farmed fish as a nonindigenous species in Iran. Eyed eggs have been imported from different countries to Iran. In this study, genetic diversity of 50 fish (male and female) from Iranian generation and 24 fish from French generation were evaluated. Six microsatellite markers including OMM1019 ،OMM1036 ،OMM1307 ، OmyFGT5TU ،Omy77DU and Omy207UoG were applied. Average number of observed alleles in the Iranian and the French stocks were 6.68 and 6.83, respectively. Average number of effective alleles in the Iranian and French stocks were 3.13 and 3.45, respectively. Mean expected and observed heterozygosis was 0.68, 0.53 and 0.71, 0.61 in Iranian and French stocks, respectively. The results showed significant deviation from Hardy-Weinberg equilibrium at the most of loci × stock. Fixation index Fst calculated based on allelic frequency between two stocks was 0.058 with significant difference between 2 stocks. The results of this study showed insignificant genetic differentiation based on six microsatellite loci.

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In order to investigate the effect of different temperature of anesthetic (clove tree) and recover (anesthetic-free water) solutions on recovery process, The anesthetic induction times and recovery times of 540 fingerlings of rainbow trout (Oncorhynchus mykiss) weighing 3.2 ± 0.2 g in anesthesia/ recovery solutions with cross-combined of temperature of 5,11 and 17 °C as experimental treatments (9 treatments) were compared. The anesthesia was induced by170 ppm of aqueous clove (Eugenia caryophyllata) solution. Results showed that both induction and recovery times were adversely temperature-dependent. Recovery times of treatments, related to temperature of anesthetic solutions and their temperature, were significantly different (P < 0.05). Our results indicated that mean recovery time (three temperature treatments) of the fish exposed to the lower temperature anesthetic solutions generally decreased opposing with higher anesthetic solutions. The lowest recovery time (61±11.1 seconds) in17°C anesthetic-free water occurred in fishes induced to 5°C anesthetic solution. In contrast, the highest recovery time (523±154 seconds) in 5°C water happened in fishes induced to 17°C anesthetic solution. Warm and cold thermal difference in anesthetic and recover solutions could extend recovery time 1 up to 8 minutes. Regarding to aim and demanded time, by selected favorite temperatures can control anesthesia/or recovery time in

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This study investigated the ontogeny of some digestive enzyme and explored the effects of photoperiod on stomach (pepsin) and intestine enzyme activity (alkaline phosphatase and N-amino peptidase) in rainbow trout (Oncorhynchus mykiss) larvae juvenile. About 3600 larval rainbow trout in first feeding (18 days after hatching) with an average initial weight 119±0.009 mg were distributed in plastic tanks in four treatments (300 larvae in each replicate). Four light treatments consisting of 14 to 10 h, 10 to 14 h, 4 to 20 h and 24 to 0 h (light: dark), were compared in triplicates for 6 weeks.. Finally, a random sampling from larvae was undertaken on days 1, 3, 5, 8, 10, 15, 20, 25, 30, 39 and 44 days after the onset of first feeding. According to the results, the digestive enzymes activity in fish larvae and juveniles had a similar change trend with age at all photoperiods. In addition, at the end of experiment, the specific activity of pepsin and N-amino peptidase were the highest in 24h Light treatment, but there was no significant difference in specific activities of alkaline phosphatase (p>0.05). The results demonstrated that growth and digestive enzymes activity of rainbow trout larvae and juvenile are improved by applying of longer photoperiod in rearing conditions.