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

Genetic variations of Iranian and French stocks of rainbow trout (Oncorhynchus mykiss)

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

Induction of population triploid-interploid in rainbow trout (Oncorhynchus mikiss) using by indirect

Induced polyploidy is a suitable tool for producing sterile fish which made commercial benefits in the aquaculture industry. This study carried out in order to produce triploid-interploid population via mating tetraploid female with diploid male rainbow trout. Heat shock was used for making tetraploid population and the best temperature and induction time were examined. Result showed that highest mortality from 1 day after fertilization to emerging were in groups 6 of embryos (40.1%) and the lowest were in groups 3 (33 %). Flowcytometry results showed that some fish were polyploidy. Comparative analyze of genome levels in tetraploid fish to control fish (diploid) and hen as standard indicator, confirmed tetraploid fishes in this study. In conclusion we can state that heat shock induction for 7 minutes at 65 hour –degree after fertilization in 28ºC is optimum temperature for inducting tetraploid rainbow trout

Comparison of growth and survival rate between import and native rainbow trout (Oncorhynchus mykiss)

Rainbow trout is only species of cold water fishes which is rearing and propagation in Iranian fishery farms. Along of develop aquaculture industries increase request of best produces such as trout eyed eggs and larva. For this reason fishery farmers must be to provide that the way of import of other countries, such as: Denmark, Norway and France. As for this importance subject and unknown basic information about preference ratio for doing it, we needed to study about that to answer the suppliant questions. In this study carried out 3 test groups (3 treatments with 3 repetitions) and compared specific growth rate (SGR), condition factor (CF) and survival rate (SVR) between in this groups. Statistical analysis were significantly difference of increase rate of length and weight in French group with other groups (p<0.05). Compared of main factors (SGR, CF, SVR) in French test group were significantly difference with other groups (p<0.05). Survival rate percentage in Iranian treatments (SVR=%67) were significantly with the others (p<0.05). This ratio respectively in Danish and French treatment was %54 and %48

Investigation of chromosome and ploidy levels of rainbow trout produced from imported eyed eggs

Rainbow trout is the main cultural species of coldwater fishes in iran. Often, aquaculturists intend to breeding in order to production of lines with higher growth rate potential and disease resistant. Nevertheless in the country, no trout breeding programs, has been performed yet and most of the farms focused on the cultivation of the first (unbred) race. While European countries progressed in trout breeding techniques and production lines with higher growth through genetic manipulation (chromosomal number and type changes of fish) and/or selection and their fish products derived from this technology, including eyed eggs and so on have sold to other regions of the world (eg: Iran). In this study, some biological parameters including survival, growth, feed conversion ratio (FCR.) and chromosomal number of two juvenile groups from imported( group 1) and native(group 2) eyed fish eggs were compared. For chromosomal investigation, blood smear test and flow cytometry were performed. sults showed a significant difference (P≤5%) in growth rate of native fishes and French group Native fish feed conversion ratio (0.9) was significantly difference (P≤5%) from that of French fishes (1.15). Chromosomal analysis showed no difference in chromosome number in treatments and two fish groups were 2n chromosome. Based on the results, the fishes of group 1 had faster grow potential and gain weight in less time than that of group 2 and this has been achieved to go through the process of selection and feminization without any change in number of ploidy. Whereas the ability of native fishes in food efficiency ( lower FCR.) was better. However, the reduction of rearing period is the benefit and preference of cultivation of imported or origionally foreign

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

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