Investigation on replacement of fish oil by vegetable oils (rice bran, soybean and linseed) in diet of rainbow trout (Oncorhynchus mykiss)

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, soybean 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

The study on culture of rainbow trout (Oncorhynchus mykiss) by new design of foster-lucas ponds

Intensive culture of rainbow trout, usually done using several different methods. The objective of this study was to compare fish performance and welfare in a new design of Foster-lucas ponds (FLP) and a raceway ponds (RP) under field conditions. Currennt study was designed in two treatment with three repeats. Each pond was randomly stocked by rainbow trout fish with initial average weight of approximately 51±5 g. stocking density was 120n/m3 during study. After 10 months of trial, fish fed diets with commercial diet (Chineh Company). Feeding operation conducted according to the manuals by consideration of water temperature, fish weight and biomass. During the 10 months experiment, the fish survival rate was high (97.39 and 98.05%). No significant differences in growth parameters were observed between RP and FLP, but in all parameters FLP was higher than RP Final weight was 0.99% higher in FLP than in RP. Water quality factors (Dissolved oxygen, PH) was better in FLP. The results confirm that when water quality is maintained in safe level ranges, growth rate of rainbow trout attained in FLS are comparable to those in RP

The production of all-female in rainbow trout (Oncorhynchus mykiss) using indirect feminization

The sex reversal technique in fish is widespread in many countries. The development of these techniques is desirable because rainbow trout males reach their gonad maturity earlier compared to the females. Rainbow trout alevins were treated with 17α-methyltestosterone incorporated in the diet (0.5. 1.5, 3, 6 and 10 mg/kg) for 60 days from the beginning of first feeding. Sex was determined at 180 and 680 dpf by sampling fish (n = 20) from each group and examining gross gonadal morphology under a dissecting microscope. Also sex reversal ratio and growth performance were determined in hormone-treated groups. These sex reversed functional males were reared for brood stock until they attained sexual maturity. At the end of experiment, normal rainbow trout eggs were fertilized with the sperms taken from sex reversed males for producing all-female populations. Examination of the results showed that 17α- methyltestosterone was effective in all treatment. The highest sex reversal ratio with 100% was observed in group treated with 0.5, 1.5 and 3 mg/kg 17α- methyltestosterone. The highest live weight ratios were observed in groups fed with 6, 0.5 17α-methyltestosterone and control group. Female progeny produced from the sex reversed males were 100 % in all males that sired offspring. All female trout stocks produced by this method have advantage in rainbow trout culture since the fish is not meant for direct human consumption and is used to generate brood stock, therefore, difference of growth parameters do not influence the success

Evaluation of sperm quality and different nutrient levels on sperm efficiency in male rainbow trout

Considering the importance of rainbow trout (Oncorhynchus mykiss) in supplying required protein of people and effort to increase the efficiency of these fish reproduction, some related factors such as sperm quality and potential fertility of male are necessary. The aim of this study was to find out the effects of different dosages of Arginine on the biochemical parameters (including LDH, AST, ALT, ALP, iron, magnesium, phosphorous, chloride, calcium, sodium, Potassium, cholesterol, uric acid, urea, fructose, glucose, total protein and pH) of rainbow trout seminal plasma. For this purpose, five practical diets (each consisting of 3 triplicates) were supplemented with Arginine at 0.00 (Control), 0.50, 1.00, 1.50 and 2.00%. Broodstock feed last for 90 days. At the end of the feeding period one fish was captured from each replicate in order to collect their semen. Results indicate that there were no significant differences in LDH, ALP, Fe^2+ and P content among different treatments. The lowest level of AST and ALT and the highest level of Ca^2+ and Mg^2+ ions were observed in the treatment fed with 1.50% of Arginine which showed significant differences with other treatments (p<0.05). Moreover, the amount of Cl^-, Na^+ and K^+ ions were significantly increased in the seminal plasma in fish which were fed on diets containing arginine in comparison to control. As the amount of Arginine were increased, the levels of uric acid stepped up significantly in contrast to the urea and glucose. The highest amounts of cholesterol, fructose and total protein were observed in the treatments fed on 2.00, 0.50 and 1.00% of Arginine, respectively, that showed significant differences with other treatments (p<0.05). The highest pH value was assayed in the 1.50% of Arginine treatment. The results of the Pearson correlation coefficient showed a significant positive correlation between Ca^2+ and Mg^2+ ions and Na^+ with K^+ and Clions (r=0.750, r=0.769 and r= 0.938, p<0.01), respectively. On the other hand, a significant negative correlation between cholesterol with Cl^-, Na^+, K^+, ALT and LDH (r=- 0.764, r=-0.724 and r=-0.728, p<0.01) and (r=-0.531 and r=-0.560, p<0.05) and also a significant positive correlation between K^+ and Clions (r=0.836, p<0.01) were observed. Finally, it can be expressed that the levels of most of the ions were increased and there was a reduction in the levels of enzymes in seminal plasma of fish which were fed with practical diet including 1.5% of Arginine. So it can be recommended that adding this value of Arginine to the diets of rainbow trout broodstock, would improve the sperm quality which results in the enhancement of efficiency in rainbow trout reproduction

The creation of genetic basic population of rainbow trout (Onchorhynchus mykiss) based on study of genetic variation in brood stocks using microsatellite

In order to perform the project, 446 samples of rainbow trout (Onchorhynchus mykiss) from 24 different regions in Iran were collected. About 2-3 g of caudal fin samples was collected from each specimen and preserved in absolute ethyl alcohol and then 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 10 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 allelic frequency, effective number of allele, observed and expected heterozygosity, shanon index, measurement of similarity and genetic distance and Hardy-Weinberg equilibrium, Fst , Rst and gene flow were calculated using AMOVA analysis in the GenAlex and Popgene programs. The results showed that 8 pairs of microsatellite primers were polymorphic. In total, 50 alleles were determined with the range size of 64-280 bp. The locus omyf had maximum number of allele (26) and loci OTSG 474 and Strurruta58 had minimum number of allele (5). The observed heterozygosity was between 0.86 and 0.964. Hardy-Weinberg departure was observed for all loci from farms 18, 15, 4, E20 and 21 and were disequilibrium (P<0.05). The farms 14, 8, 7 and 6 were equilibrium at 3 loci, but showed disequilibrium in other loci. The other farms were equilibrium at 1 or 2 loci and disequilibrium at 8 or 9 loci. The FST results showed that maximum FST (0.24) were between farms 1 and 11in which had minimum of gene flow (3.7). Minimum FST (0.04) were between farms 8 and 9 in which had maximum of gene flow (346). Based on the results of AMOVA analysis, significant differences were detected between all farms (P<0.01). Furthermore, based on Nei 's standard (1972) maximum genetic distance (0.89) were observed between farms 2 and 11 and maximum genetic similarity (0.15) were detected between farms 3 and 4. This result suggests 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

Cryopreservation of rainbow trout (Onchorhynchus mykiss) semen

Breeding has moved beyond the point of simply propagating random stock. Genetic potential can be improved by establishing and crossing genetically defined strains, crossing species and manipulating gametes. Some of these activities require cryopreservation of semen. Cryopreserved sperm could also be a means of exchange of genetic material between locations and populations when transportation of live fish is restricted. In this study we had a survey on rainbow trout sperm quality in Genetic and Breeding Center for Coldwatwr Fishes, Shahid Motahari, Yasouj. Then Cryopreservation trials on rainbow trout (Oncorhynchus mykiss) sperm were carried out using six basic extenders. Egg batches of 25 g were inseminated with semen frozen in five 0.5-ml straws. Thowing temperature of cryopreserved sperm also was tested. In anather trial we investigate different cryoprotectant. The result showd that the best period for sperm collection in this center was from Novamber to January. The best extender based on sperm motility parameters were extender 2 and 1 with 57.2 and 56.9% fertilisatin rates, respectively. So this two extender were used in the further experiments. The best thowing temperathre was 25°C in 30s. Testing different cryoprotectant, adding 10% methanol to extender 1 gave the highest fertilization rate (64.6%) among cryoprotectant that used with this extender. In the other extender (2) adding 5% DMSO and mixture of 5% DMSO and 1% glycerol gave the highest fertilization rates (64.8% and 67.0%, respectively). In conclusion using extender 1 and 2 with mentioned cryoprotectant and thowing rate of 25°C in 30 s was recammended for rainbow trout sperm cryopreservation