Nile Tilapia Strains Research Articles

Intraperitoneal Germ Cell Transplantation in the Nile Tilapia Oreochromis niloticus

Germ cell transplantation offers promising applications in finfish aquaculture and the preservation of endangered species. Here, we describe an intraperitoneal spermatogonia transplantation procedure in the Nile tilapia Oreochromis niloticus. Through histological analysis of early gonad development, we first determined the best suitable stage at which exogenous germ cells should be transplanted into the recipients. For the transplantation procedure, donor testes from a transgenic Nile tilapia strain carrying the medaka β-actin/enhanced green fluorescent protein (EGFP) gene were subjected to enzymatic dissociation. These testicular cells were then stained with PKH26 and microinjected into the peritoneal cavity of the recipient fish. To confirm colonization of the donor-derived germ cells, the recipient gonads were examined by fluorescent and confocal microscopy. PKH26-labeled cells exhibiting typical spermatogonial morphology were incorporated into the recipient gonads and were not rejected within 22days posttransplantation. Long-term survival of transgenic donor-derived germ cells was then verified in the gonads of 5-month-old recipients and in the milt and vitelogenic oocytes of 1-year-old recipients, by means of PCR using EGFP-specific primers. EGFP-positive milt from adult male recipients was used to fertilize non-transgenic oocytes and produced transgenic offspring expressing the donor-derived phenotype. These results imply that long-term survival, proliferation, and differentiation of the donor-derived spermatogonia into vitelogenic oocytes and functional spermatozoa are all possible. Upon further improvements in the transplantation efficiency, this intraperitoneal transplantation system could become a valuable tool in the conservation of genetic resources for cichlid species.

Comparative Performance of Four Strains of Nile Tilapia (Oreochromis niloticus) in Brackish Water Ponds in Indonesia

Four selectively bred strains of Nile tilapia (Oreochromis niloticus) were evaluated for production in brackish water ponds in Indonesia. Survival to 124 days was relatively low for all four strains (39%–48%), and growth during the later stages of the trial was poor (SGR < 1.5 %/day) due to water quality deterioration in the pond. Although the ‘Red’ tilapia strain demonstrated the best production parameters, red-colored tilapia bring lower prices in both our test markets (South Sulawesi and Aceh provinces). Of the four strains, the genetically enhanced supermale Indonesian tilapia × genetic improvement of farmed tilapia (GESIT×GIFT) cross provided the best economic return.

Genetic parameters for reproductive traits in female Nile tilapia (Oreochromis niloticus): II. Fecundity and fertility

Harvest weight is the main trait in Nile tilapia (Oreochromis niloticus) breeding programmes. The effects of selection for harvest weight on female reproductive traits are unknown. In this paper we estimate genetic parameters for reproductive traits and their correlation with harvest weight using females from the generation 12 of the GIFT strain of Nile tilapia in the Mekong Delta of Viet Nam. Spawning records were obtained from single pair mating as well as group mating experiments. The traits were categorised into two groups: fecundity-related traits and fertility-related traits. Fecundity traits were: number of eggs (NEGG), relative fecundity as the ratio of number of eggs to female spawning weight (RFEC), egg weight (EGGW) and egg diameter (EGGD); fertility traits were: number of fertilised eggs (FEGG), number of hatched eggs (HAT), number of swim-up fry (SWUP), and fertilisation rate (FER, in %). Heritability estimates for fecundity traits were low, ranging from 0.05 to 0.08. Heritability estimates for fertility traits were also low, ranging from 0.06 to 0.12. Genetic correlations for HW with NEGG and TEGGW were positive (0.51 and 0.42, respectively), while correlations for HW with RFEC, EGGW, and EGGD were negative (−0.72, −0.48, and −0.50, respectively). The same trend was observed for body weight at spawning (SPW), but genetic correlations between SPW and fecundity traits were higher than those between HW and fecundity traits. Genetic correlations between HW and fertility traits were all moderate to high (0.46 to 0.69), except for FER (0.15±0.24). Genetic correlations between SPW and fertility traits were even higher (0.69 to 0.93). We conclude that both HW and SPW have favourable genetic correlations with NEGG, RFEC, and SWUP, which are the desired characteristics for Nile tilapia seed production. Selection for HW does not affect these traits. However, Nile tilapia females selected for large HW tend to produce smaller eggs. We recommend monitoring the phenotypic and/or genetic trend in this trait, as smaller eggs might, on the longer term, lead to lower fry survival.

Combined effect of temperature and salinity on the fertilization and hatching rate in the GIFT strain of Nile tilapia, Oreochromis niloticus

We evaluated the effect of temperature and salinity on the artificial fertilization rate(FR,%) and hatch-ing rate(HR,%) in the GIFT strain of Oreochromis niloticus using a Central Composite Design and Response Surface method.The fish were reared in temperatures ranging from 20?34?C and the salinities ranging from 0?18.Both FR and HR decreased as temperature and salinity approached the lower and higher bounds.HR and FR were significantly affected by the linear and quadratic of temperature and salinity(P0.001).However,there was no evidence for a synergistic effect between temperature and salinity(P0.05).After correcting for the negative cor-relation coefficient,the r2 values for the equations explaining temperature and salinity were 0.957 8 and 0.960 1,respectively(P0.01).Thus,these models can be used to forecast HR and FR in Nile tilapia.The highest FR(80.81%) and HR(77.63%) were observed eggs incubated at 27.14?C and 8.95 of salinity.Our results may be used to improve fertilization and hatching success in cultured strains of Nile tilapia.

Growth comparison among three strains of Oreochromis niloticus juvenile in net cage under different salinity-alkalinity waters

We chose Nile tilapia Oreochromis niloticus juvenile from Shanghai,Shandong and Hebei strains,which were chronically acclimated,as experimental groups,and studied their survival rate and average growth rate in net cage under different salinity waters(0,15,20),NaHCO3 alkalinity waters(1 g · L-1,2 g · L-1,3 g · L-1),and salinity-alkalinity waters(15,1 g · L-1;15,2 g ·L-1;15,3 g · L-1;20,1 g · L-1;20,2 g · L-1;20,3 g · L-1).The 62 days experiments show that there is no significant difference in the survival rate among three strains under different salinities,alkalinities and salinity-alkalinity waters(P0.05),while there is significant difference in average growth rate(P0.05).The average growth rate of three strains roughly tend to decline with increasing salinity and alkalinity,while the growth rate of salinity-alkalinity group increases slower than those of treated with salinity and alkalinity.Besides,Shanghai,Shandong and Hebei strains show some relative growth advantages in different salinity and alkalinity gradients,respectively.The study provides some basic data for determination of optimum growth salinity-alkalinity and for selection of Nile tilapia strain.

&lt;b&gt;Growth curves of Nile tilapia (Oreochromis niloticus) strains cultivated at different temperatures&lt;/b&gt; - doi: 10.4025/actascianimsci.v35i3.19443

Growth of Red, GIFT and Supreme Nile tilapia strains were evaluated. Fish were cultivated in indoor recirculation systems in 0.5 m³ tanks with controlled temperatures of 22, 28 and 30°C. Random samples of 20 fish from each strain (10 fish tank -1 ) were weighed at day 7, 30, 60, 90 and 120. Exponential model (y=Ae Kx ) and Gompertz model (y = Aexp(-Be -Kx )) were fitted and the estimates parameters were obtained by Weighted Least Squares. At 22°C, Red, GIFT and Supreme strain presented similar growth and fit of exponential model. GIFT and Supreme strain presented higher growth rate at 30°C of cultivation when compared to Red strain. Temperature influences weight and age at the inflection point. The temperature of cultivation influences the growth description of Red, GIFT and Supreme tilapia strains. It changes the age and weight at inflection point and the qualities of growth model fits, changing the variation of the batch.

Physiological responses and HSP70 mRNA expression of GIFT strain of Nile tilapia (Oreochromis niloticus) under cold stress

An investigation on the physiological responses and HSP70 expression under cold stress was conducted on Genetically Improved Farmed Tilapia (GIFT) strain of Nile tilapia (Oreochromis niloticus). Tilapia were acclimated at 28°C as control and then the water temperature was reduced from 28°C to 15°C at a rate of 1°C h−1, and serum biochemical indices, antioxidant enzymes and expression of HSP70 mRNA were analysed on days 0, 0.5, 1, 2, 3 and 5 after exposure to 15°C. The concentration of serum K, Na, Cl and Ca concentration showed instability during cold stress. Glucose rapidly increased on day 0 followed by a declining trend. Triglyceride, cholesterol, low density lipoprotein-cholesterol signifi-cantly decreased and high density lipoprotein-cholesterol showed instability during cold stress. Aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase activities were prominently elevated under cold stress. Superoxide dismutase and catalase activities showed a remarkable rise on day 0.5 under cold stress, and gradually decreased thereafter. HSP70 mRNA level significantly increased both in liver and muscle under cold stress, especially on days 0.5 and 1. These results suggest that cold influences several physiological responses of tilapia, and the cold resistance and cold tolerance of tilapia will benefit from the enhancement of antioxidant enzymes activities and upregulated HSP70 mRNA expression.

Reproductive performance in female strains of Nile tilapia, Oreochromis niloticus

The Nile tilapia is among the most cultivated tropical fish in the world, yet little is known about the variations in reproductive characteristics among different strains. There is an interest in evaluating the reproductive performance of females of three tilapia strains. All strains were represented in equal proportion (n = 225), being named as Supreme (SUP), Premium Aquabel (PA), and Chitralada (CHI). These fish were cultivated for 7 weeks in the Aquabel Pisciculture Station (Brazil), from January to March 2011. The PA was the largest strain, with the highest values in all the morphometric parameters we analyzed (weight, total length, standard length and body depth). Among the evaluated reproductive parameters, the PA strain differed significantly from the other two in number and weight of eggs/female, volume of eggs/spawn and number of eggs/kg of fish. The percentage of non-spawning females in the SUP and CHI strains differed significantly from one another, while results for PA showed intermediate values and no significance compared to the other strains (P > 0.05). Among the reproductive parameters analyzed, the percentage of spawned females/week, more than one spawns during 7 weeks, and hatching rate showed no significant differences between strains (P > 0.05). There was a significant correlation (r = 0.69) between water temperature and percentage of spawned females/week. When evaluating the interval between two consecutive spawns, we observed that periods of 21 days were the most frequent in all strains. In conclusion, the strain that showed the best results in all morphometric and in most reproductive parameters we evaluated was the PA.

A comparison of microsatellites and SNPs in parental assignment in the GIFT strain of Nile tilapia (Oreochromis niloticus): The power of exclusion

In this study, parental assignment was studied in the 10th generation of a pedigreed selected Nile tilapia (Oreochromis niloticus) population (GIFT) and their offspring, by comparing two types of molecular markers, microsatellites and SNPs, using an exclusion-based (Vitassign) and a likelihood-based (Cervus) method. For the experiment, G10 parents were divided in 4 groups (cohorts) and allowed to produce offspring by natural group mating. In total 173 offspring were tested against 238 parents, using either 12 microsatellites (PIC=0.639; exclusion power 68.0%) or 122 SNPs (PIC=0.341; exclusion power 99.9%). In this study, more than half of the candidate parents were either full- or half-sibs with other parents. Furthermore, 13.8% of the parents died before being sampled for DNA.When offspring were assigned to parents in the same cohort, using Vitassign, for microsatellites, allowing up to 2 mismatches, 37.6% offspring got unique assignments, 45.1% got multiple assignments, and 17.3% were not assigned; for SNPs with up to 15 mismatches allowed, 83.8% offspring got unique assignments while 13.9% got multiple assignments. Only 2.3% were not assigned. Using Cervus, for microsatellites, the mean ‘strict’ (>95% CF) assignment rate across the 4 cohorts was 18%, the ‘relax’ (80–95% CF) assignment rate was 43%, and 39% were not assigned; for SNPs, 39% ‘strict’ assignments were obtained (mean across 4 cohorts); the remaining offspring were not assigned. In general assignment rates were higher when cohort offspring were assigned to all parents combined, irrespective of method (Vitassign or Cervus) or marker used. However, consistency of assignments between microsatellites and SNPs was low: 28% with Vitassign and 16% with Cervus. Consistency of assignments between Cervus and Vitassign was high with SNPs (65%), but was low with microsatellites (31%). We conclude that missing parents and relatedness among candidate parents resulted in low assignment rates. Furthermore, low exclusion power of the microsatellite set resulted in low assignment rates and multiple parent pair assignments irrespective of method used. Exclusion methods and likelihood-based methods can be equally good for parental assignments, providing that good marker sets with high exclusion power are available.

Effect of low temperature on genomic DNA methylation in Nile tilapia (Oreochromis niloticus)

In this study,using the methylation sensitive amplified polymorphism(MSAP) method,we globally assessed the effect of low temperature adaptation on the level and variations of cytosine methylation alterations at CCGG sites of genomic DNA in Nile tilapia(Oreochromis niloticus) strains with good coldresistance characters developed by the successive and directional selection breeding of multi-generations. Total of 849 fragments were identified by 18 pairs of se1ective primer combinations of which 411 and 438 were detected in cold-resistance tilapia strain and the control,respectively. Among these fragments,the methylation sites were 72 and 104,and the corresponding total-methylation levels w ere at 17.52% and 23.74%,respectively. The full methylation sites at the internal Cs were 37 and 65,and the corresponding full methylation levels were at 9. 00% and 14. 84%,respectively,and the hemi-methylation sites at the external Cs were 35 and 39,and the corresponding hemi-methylation levels were at 8.52% and 8.90% in coldresistance tilapia strain and the control,respectively. Further analysis of DNA methylation indicated that a statistically decrease in the overall level of total-methylation levels and both methylation types was detected in cold-resistance tilapia strain compared with the control(decrease at 6.22%,5.84% and 0.38%, respectively),and the changes of DNA methylation pattern were recognized mainly in the full methylation sites. The level of decrease in DNA methylation suggested that the levels of genomic DNA methylation were changed during the successive cold stress of multi-generations in tilapia,and it also indicated that DNA methylation alteration in tilapia treated with cold stress was mainly through de-methylation that occurred in some CCGG sites. All these results implied that the change of DNA methylation was closely associated with cold tolerance of tilapia. The present findings are valuable to further explore the application potential of DNA methylation alteration in tilapia genetic improvement and provide a new method and theoretical basis for fish stress resistance breeding.

The combined effect of environmental thermal drop and isotonicity on metabolic stores of the teleost, Oreochromis niloticus

Four experimental regimes were designed to test the capacity of the Nile tilapia Oreochromis niloticus to make use of the energy saved form osmoregulation in an isotonic medium in overcoming the Winter Stress Syndrome (WSS). Fish either pre- acclimated to freshwater or isotonic salinity at 25°C were transferred directly to freshwater or an isotonic medium (ca. 12‰) at 14°C. Fish were killed 3, 6, 24, 48, 72 and 168h after transfer. The mobilisation and use of lipids from perivisceral and muscle fat observed in the study seem to be a direct response to cold stress as well as the associated fasting, these effects were salinity dependent being lesser at the isotonic salinity. The energy needs of fish diminish in cold conditions when the salinity of the environment approaches the isotonicity. The absence of any significant changes in muscle and water content indicated that the changes of muscle lipid are true and lipid was the sole source of energy upon thermal drop. The changes of blood haemoglobin levels throughout the four experimental regimes may indicate that the isotonic medium acclimated tilapia showed less haematological disturbance due to cold stress. Results from this experimental study recommend that the pre-acclimation of the Egyptian strain of Nile tilapia, O. niloticus, to an environmental salinity close to the isotonicity may improve fish cold tolerance.

Effect of Dietary Fish Meal Replacement by Canola Meal on Growth Performance and Hepatic Intermediary Metabolism of Genetically Improved Farmed Tilapia Strain of Nile Tilapia, Oreochromis niloticus, Reared in Fresh Water

An 8‐wk feeding trial was conducted to evaluate the potential of replacing fish meal with canola meal in experimental diets for genetically improved farmed tilapia (GIFT) strain of Nile tilapia, Oreochromis niloticus (mean initial weight: 20.0 ± 0.62 g, means ± SD), reared in fresh water. Six isonitrogenous (30% crude protein) and isolipidic (10%) diets were formulated with canola meal included at six levels of 0 (control), 11, 22, 33, 44, and 55%, replacing 0, 15, 30, 45, 60, and 75% fish meal, respectively. Growth performance and feed utilization showed no significant differences among the treatments. In general, dietary canola meal supplementation showed significant effect on hepatic composition of tilapia, but not muscle composition. Viscerosomatic index tended to increase with increasing dietary canola meal levels from 0 to 44%, and then declined when dietary canola meal levels further increased from 44 to 55%. Dietary fish meal replacement by canola meal significantly influenced several hepatic enzymatic activities, including succinate dehydrogenase, lactate dehydrogenase, malic dehydrogenase, lipoprotein lipase, and hepatic lipase, suggesting that dietary fish meal replacement by canola meal had significant effects on nutrient metabolism in the liver. Based on the information above, 75% of dietary fish meal could be replaced by canola meal with no effect on growth performance of GIFT strain of Nile tilapia. Use of canola meal in practical diets for GIFT stain of Nile tilapia may allow producers and feed mills to formulate more economical diets.

Complete Genome Sequence of Streptococcus agalactiae ZQ0910, a Pathogen Causing Meningoencephalitis in the GIFT Strain of Nile Tilapia (Oreochromis niloticus)

Streptococcus agalactiae (group B streptococcus [GBS]) is a pathogen that causes meningoencephalitis in Nile tilapia (Oreochromis niloticus). Here, we reported the complete genome sequence of S. agalactiae strain ZQ0910, which was isolated from the GIFT strain of Nile tilapia in Guangdong, China.

Growth and survival rate of three genetic groups fed 28% and 34% protein diets

The strain by nutrition interaction in body weight and survival rate was examined by testing three genetic groups (Selection and Control lines of the GIFT strain, and Red tilapia) at two levels of protein in the diet (28% and 34%). The GIFT strain of Nile tilapia (Oreochromis niloticus) has been selected for high-breeding values for body weight, whereas the Control was contemporaneously maintained and selected for breeding values of body weight close to the population mean. The Red tilapia (Oreochromis spp) was unselected at the time of the experiment. There were a total of 6000 fish at stocking in the study (2000 fish per genetic group). During the grow-out period of 147 days, within each genetic group, the fish were randomly assigned to either a 28% or a 34% protein diet. Survival rate during grow-out averaged 72%. A total of 4335 fish were harvested, with individual body measurements and survival recorded. The effect of genetic group accounted for the largest proportion of variation in body weight and survival, followed by sex and protein level. Across the two dietary protein levels, the GIFT strain had the highest growth. The difference in body weight between the Control and Red tilapia was not statistically significant (P > 0.05). Responses in growth to dietary protein levels also differed between genetic groups. No differences (P > 0.05) in body weight were found in the GIFT selection and Control fish fed 28% or 34% protein diets. However, body weight of Red tilapia was greater in the high- than in the low-protein diet. In contrast to body weight, survival rate from stocking to harvest was affected by protein level. The high-protein diet significantly improved survival rate, averaging 24% across the three strains. The overall results indicate significant effects of genetic group and dietary protein level on both body weight and survival rate; however, the interaction between strain and dietary protein levels was small and possibly unimportant for these traits. It is concluded that the 28% protein diet used in the selection programme for the GIFT strain results in the selection of genotypes that can perform well under commercial feeds.

Morphological variability of the 11th generation strain of nile tilapia, (Oreochromis niloticus) and traditional genetically improved farmed tilapia

To investigate the morphological variations 12 morphometric and 11meristic characters were studied for 100 individuals of the same age of traditional strain GIFT (5th generation) and recently developed 11th generation strain (GIFU) of Nile tilapia, Oreochromis niloticus. No significant difference was found between total length and other body measurements at 5% level. However, GIFU showed faster linear growth on body depth, maximum body circumference and minimum body circumference where GIFT showed faster linear growth on standard length and head length. On meristic characters, notable variations were observed in case of scale above and below the lateral line, where GIFU individuals showed greater number of scales in both cases. The total length and body weight relationship of both the strains were found to be straight line in logarithmic scales. The mean values of condition factor (K) have been found to be 1.671 for GIFT and 1.711 for GIFU and the mean values of relative condition facto (Kn) were 1.001 and 1.002 for GIFT and GIFU respectively. Findings of the present study suggested the variability of strain GIFU and GIFT in some important parameters. DOI: http://dx.doi.org/10.3329/jbau.v9i2.11050 J. Bangladesh Agril. Univ. 9(2): 345–349, 2011

Differential expression patterns of growth-related microRNAs in the skeletal muscle of Nile tilapia (Oreochromis niloticus)1

MicroRNA (miRNA) are a class of small, single-stranded, non-coding RNA that regulate mRNA expression at the post-transcriptional level and play important roles in many fundamental biological processes. There is emerging evidence that miRNA are critical regulators of widespread cellular functions, such as differentiation, proliferation, and migration. At present, little is known about miRNA expression profiles related to skeletal muscle growth in aquatic organisms. This study aimed to investigate the phenotypic variation in the body growth of the Nile tilapia (Oreochromis niloticus) and to identify and quantify the differential expression levels of selected growth-related transcriptomic miRNA in the skeletal muscle of this fish. To this end, we performed next-generation sequencing to define the full miRNA transcriptome in muscle tissue from Nile tilapia and to detect differentially expressed miRNA between 2 strains of Nile tilapia. These tilapia strains exhibited significant (P < 0.05) phenotypic variation with respect to growth-related traits (body length and BW), mitochondrial DNA (mtDNA) haplotype diversity, and the differential expression of selected growth-related genes. The results obtained from the transcriptome analysis and real-time quantitative reverse transcription PCR (qRT-PCR) revealed significant differences in miRNA expression between fast-growing and control strains of tilapia. Digital gene expression (DGE) profiling was performed based on the obtained read abundance, and we identified down-regulated miRNA, including let-7j, miR-140, miR-192, miR-204, miR-218a, miR-218b, miR-301c, and miR-460, and up-regulated miRNA, including let-7b, let-7c, miR-133, miR-152, miR-15a, miR-193a, miR-30b, and miR-34, associated with body growth in tilapia. These results were further validated using real-time qRT-PCR and microarray profiling. In summary, the up- and down-regulation of miRNA involved in the GH/IGF-1 axis signaling pathway suggests that the differential expression levels of growth-related miRNA may serve as molecular markers that are predictive of specific functional and diagnostic implications. The obtained data on genetic polymorphisms in miRNA-target interactions are particularly useful for Nile tilapia breeding programs.

Evaluation of Nile tilapia strains cultivated in cages under different feeding programmes

The objective of this study was to evaluate the performance of three Nile tilapia Oreochromis niloticus strains cultivated in cages and subjected to different feeding programmes. Initially, 31,200 Nile tilapia juveniles with an average weight of 61.15 g were distributed in 48 cages. Two genetically improved strains were used together with one from the Fish Culture Section of Universidade Federal de Lavras (UFLA). The fish were subjected to four feeding programmes, consisting of different levels of crude protein (CP) in diets provided at different stages of cultivation. There was no interaction effect of the strain and feeding programme for most variables. The UFLA strain presented the highest weight gain, but with greatest lack of uniformity at the end of cultivation. The feeding programme with diets containing 36%, 32% and 28% CP, consecutively, promoted the highest weight gain and highest final biomass. The UFLA strain has great growth potential, justifying the development of a breeding programme for this strain. Crude protein levels below 36% for tilapias between 60 and 170 g and below 32% for tilapias between 170 and 700 g worsen fish performance.

SNP marker detection and genotyping in tilapia

We have generated a unique resource consisting of nearly 175 000 short contig sequences and 3569 SNP markers from the widely cultured GIFT (Genetically Improved Farmed Tilapia) strain of Nile tilapia (Oreochromis niloticus). In total, 384 SNPs were selected to monitor the wider applicability of the SNPs by genotyping tilapia individuals from different strains and different geographical locations. In all strains and species tested (O. niloticus, O. aureus and O. mossambicus), the genotyping assay was working for a similar number of SNPs (288-305 SNPs). The actual number of polymorphic SNPs was, as expected, highest for individuals from the GIFT population (255 SNPs). In the individuals from an Egyptian strain and in individuals caught in the wild in the basin of the river Volta, 197 and 163 SNPs were polymorphic, respectively. A pairwise calculation of Nei's genetic distance allowed the discrimination of the individual strains and species based on the genotypes determined with the SNP set. We expect that this set will be widely applicable for use in tilapia aquaculture, e.g. for pedigree reconstruction. In addition, this set is currently used for assaying the genetic diversity of native Nile tilapia in areas where tilapia is, or will be, introduced in aquaculture projects. This allows the tracing of escapees from aquaculture and the monitoring of effects of introgression and hybridization.

Morphological variation and mathematical analysis of effects of morphological traits on body-weight of GIFT tilapia after 3 generations of breeding

GIFT strain of Nile tilapia(Oreochromis niloticus) played an important role in world fishery.Several researches indicated that the growth performance of GIFT can still be improved.As an important indicator of breeding,body-weight was influenced by many morphological traits,and morphological traits that impact offspring body-weight might be changed after breeding,so comparative analyses of the impacts of morphological traits on body-weight between the offspring and parental generation became necessary.Sixty families of GIFT were introduced into FFRC as the parents(P) in 2006 for further study,three generations of offspring were bred(F1,F2,F3).In order to observe the achievement of breeding,body-weight(Y),body-length(X1),body-thickness(X2) and body-height(X3) of the P and F3 were measured,variation of four morphological traits of P and F3 were analyzed;correlation analysis,path analysis and regression analysis were used to calculate the correlation coefficient,path coefficient and the coefficient of determination,and the multiple regression equations between body-weight(Y) and morphological traits(X1,X2,X3)were established and analyzed.Results showed that: 1) compared with P,body-weight,body-length and body-thickness of F3 had a significant increase(P0.01),meanwhile a certain decline in the coefficient of variation(CV) was observed,body size of tilapia of F3 showed a trend of being consistent.Male of F3 had increased in some degree,significant increase of 4 traits of the male group was not observed.2) Trait af-fected the body-weight most of F3 converted to body-length,which was body-height×body-length in P.3) The influence of body-length,body-thickness and body-height on body-weight declined more in F3 than that in P.Results above indicated that,breeding made a positive effect on the growth speed of GIFT;for further study we should be more careful in selecting morphological traits,and some other morphological traits which might impact the body-weight should be taken into account for more accurate breeding project.

Genotype by production environment interaction in the GIFT strain of Nile tilapia ( Oreochromis niloticus)

Three discrete generations of GIFT fish (Nile tilapia strain, Oreochromis niloticus; a total of 10,065 fish with pedigree and phenotypic information) were tested in pond and cage culture environments to determine genotype by production environment interaction between both environments in Malaysia. Live weight (selected trait), standard length, body depth and width were recorded. A bivariate animal model was used to estimate variance and covariance components, whereby the homologous body traits in pond and cage environments were treated as genetically distinct traits. The heritabilities estimated for these body traits ranged from 0.19 to 0.40 in the pond environment, and from 0.23 to 0.34 in the cage environment. Across all traits the maternal common environmental effects ranged from 0.14 to 0.26 and were greater for the pond than for the cage environment. The genetic correlations between the pond and cage environments were 0.73 ± 0.09 for live weight, 0.81 ± 0.09 for standard length, 0.78 ± 0.10 for body depth, and 0.85 ± 0.13 for body width. Coupled with the total selection responses for live weight after two generations of selection, being 35% for the pond environment and 45% for the cage environment, we concluded that genotype by environment interaction for GIFT strain between pond and cage environments was not important. Hence, it would not be necessary to have two separate selective breeding programs for the GIFT strain in Malaysia.