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Lind C.E.,WorldFish | Safari A.,WorldFish | Agyakwah S.K.,CSIR Water Research Institute | Attipoe F.Y.K.,CSIR Water Research Institute | And 11 more authors.
Aquaculture Reports | Year: 2015

Abstract Many tilapia (Oreochromis spp.) farmers produce all-male populations because of the superior growth rate of males compared to females. To investigate differences in body weight at harvest of males and females among different tilapia strains, we analyzed data from 62,787 individuals collected from pedigreed breeding programs of O. niloticus (GIFT from Malaysia, the Abbassa line from Egypt, and the Akosombo line from Ghana), O. shiranus (the Bunda College-Domasi selection line), O. aureus (a selection line under development in Abbassa, Egypt, and a selection line from Israel) and a synthetic selection line of Red tilapia under development in Jitra, Malaysia, derived from stock from Malaysia, Taiwan and Thailand (O. sp.). Mixed models were separately fitted to the data from each selection line. There was a significant sex effect in all strains (P < 0.001). A significant (P < 0.001) sex by generation interaction was observed in all strains (scale effect, not reversal of rankings), except Red tilapia and O. shiranus. Least squares means showed a large range in the magnitude of body weight differences between sexes across the seven strains. The largest percentage difference between females and males was in O. aureus from Egypt (female body weight was 52.2% that of males at harvest), whereas the smallest difference was observed in the GIFT strain of O. niloticus (female body weight 84.7% that of males). Female to male body weight percentages for Red tilapia, O. shiranus, Egypt O. niloticus, Israeli O. aureus and Ghana O. niloticus were 81.3, 81.0, 69.1, 61.7 and 61.0, respectively. We discuss the results in relation to the potential productivity improvements due to superior growth rates of all-male culture compared to mixed-sex culture in tilapia populations differing in the female to male body weight ratio. © 2015 The Author.

Santos A.I.,State University of Maringá | Nguyen N.H.,Worldfish Center | Nguyen N.H.,University of The Sunshine Coast | Ponzoni R.W.,Worldfish Center | And 3 more authors.
Aquaculture Research | Year: 2014

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. © 2012 John Wiley & Sons Ltd.

Hamzah A.,Universiti Sains Malaysia | Hamzah A.,National Prawn Fry Production and Research Center | Nguyen N.H.,Worldfish Center | Nguyen N.H.,University of The Sunshine Coast | And 7 more authors.
Aquaculture Research | Year: 2016

The effect of selection for greater growth rate in the GIFT strain on traits related to female reproduction (weight at spawning, number of eggs, number of fry, total weight of fry and number of dead fry) was studied. Available records comprised 10 generations of data from a total of 935 breeding females with known pedigree. Female body weight at spawning was 255 g, whereas the averages for number of eggs, number of live fry at hatching, number of dead fry and total fry weight per spawning were 1444, 908, 64.90, and 7.24 g respectively. Heritabilities for reproductive traits were low to moderate (0.20 for number of eggs, 0.16 for number of hatched fry and 0.11 for fry weight per female at spawning). The genetic correlations between female body weight at spawning and reproductive traits were very low to low (0.01 to 0.31) and not significantly different from zero. The genetic correlations among reproductive traits (i.e. number of eggs, number of hatched fry and fry weight) were high (0.75 to 0.92). Phenotypic correlations were consistent with the genetic correlations, ranging from 0.56 to 0.85. Correlated responses in reproductive traits measured as differences in least squares means between Selection and Control lines were positive and significant (except for the number of dead fry) when age of females at spawning was fitted as a covariate. However, there were no significant differences in all studied traits when body weight of the female at spawning was fitted as a covariate within lines. This indicates that the greater reproductive rate was due to the greater size of females in the Selection line, but the efficiency of reproduction per unit weight of female did not change as a consequence of selection for growth. © 2016 John Wiley & Sons Ltd.

Nguyen N.H.,Worldfish Center | Ponzoni R.W.,Worldfish Center | Yee H.Y.,Worldfish Center | Abu-Bakar K.R.,Worldfish Center | And 2 more authors.
Aquaculture | Year: 2010

The quantitative genetic basis of fatty acid composition was examined in the Genetically Improved Farmed Tilapia (GIFT) strain of Nile tilapia selected for high breeding value for body weight and in the contemporaneous control selected for average breeding value. Gas chromatography analysis of 514 frozen fillet samples, obtained from the offspring of 104 sires and 154 dams from two generations in 2006 and 2007, showed that the fish possess all important fatty acids (FA), with the amount of omega-3 polyunsaturated fatty acids being 3.6%. The ratio of unsaturated to saturated fatty acids was greater than one (1.4) in the GIFT fillets, which is in line with the current dietary recommendation. Genetic analysis of FA was combined with 5532 performance and fillet records, and 2000 fillet samples analyzed for flesh composition and flesh quality attributes. A restricted maximum likelihood method applied to bivariate or trivariate mixed model was carried out in a full pedigree comprising a total of 18,970 animals to estimate genetic parameters and correlated responses in FA composition to the selection program. The estimates of heritability for individual FA varied from zero to medium, suggesting that FA composition of the GIFT fillet can respond to selection. Genetic correlations among FA within the same group (saturated, monounsaturated or polyunsaturated FA) were generally synergetic, but were antagonistic between groups. There were also both favourable and unfavourable genetic associations between important high chain polyunsaturated fatty acids and performance, fillet and flesh quality traits. Correlated changes in FA composition were measured by comparing least square means of the selection and control lines. Overall, selection for high growth resulted in very little change in FA composition. One notable change was that the content of heptadecanoic acid (C17:0) decreased in the selection relative to control line, which is beneficial for human health. In summary, the set of genetic parameters estimated and the response realized in the GIFT strain indicate that FA composition of tilapia or fish in general can be altered by genetic means. © 2010 Elsevier B.V.

Nguyen N.H.,Worldfish Center | Ponzoni R.W.,Worldfish Center | Abu-Bakar K.R.,Worldfish Center | Hamzah A.,National Prawn Fry Production and Research Center | And 2 more authors.
Aquaculture | Year: 2010

A data set consisting of 5532 slaughter records collected over three generations from a selection program for increased harvest body weight in the GIFT strain of Nile tilapia (Oreochromis niloticus) was used to estimate genetic parameters and correlated responses in body (live weight, standard length, body width and body depth) and carcass (fillet weight and fillet yield) traits. A multi-trait model using restricted maximum likelihood method was applied to a full pedigree comprising a total of 18,970 animals. The estimates of heritability for body and carcass traits were of moderate magnitude (0.20 to 0.33). The proportions of variance explained by the maternal and common environmental effects were small, ranging from 4 to 8% for body traits and fillet weight, but were negligible for fillet yield. Genetic correlations among body traits were high (0.78 to 0.95), except between standard length and body width (0.56). High genetic correlations (0.78 to 0.96) were also obtained between body traits and fillet weight, whereas those between body traits and fillet yield were generally low (0.35 to 0.44). Genetic changes were measured as the difference in least squares means between the selection and control lines. The correlated increase in fillet weight was 23% in the latest generation studied or 0.97 phenotypic standard deviation units (σP). The correlated response in fillet yield was negligible. In conclusion, selection for high growth significantly increased fillet weight. Strategies for the improvement of fillet yield in the GIFT strain are discussed. © 2010 Elsevier B.V.

Ponzoni R.W.,Worldfish Center | Khaw H.L.,Worldfish Center | Nguyen N.H.,Worldfish Center | Hamzah A.,National Prawn Fry Production and Research Center
Aquaculture | Year: 2010

A fully pedigreed population of the GIFT (Genetically Improved Farmed Tilapia) strain of Nile tilapia (Oreochromis niloticus) was established in Malaysia during 2001 and 2002. The selection program was focused on the improvement of growth rate to harvest weight and the mate allocation strategy was aimed at avoiding inbreeding and ensuring that most sire families were represented as parents of the next generation. We examined the build up of inbreeding and we estimated the effective population size by different methods (namely, from: the number of selected parents, the variance in family size, the inbreeding coefficient, and the co-ancestry among selected individuals). The rate of inbreeding was 0.0037 per generation and the effective population size calculated from the rate of increase in the co-ancestry was 88. We conclude that the mate allocation strategy has been successful in containing inbreeding and that the effective population size is satisfactory for the sustainability of the selection program. By contrast, the effective population size is below the minimum (e.g. 500) necessary for the retention of evolutionary potential, hence the population would be unlikely to adapt and cope with severe environmental challenges. The results are discussed in relation to the development and maintenance of selection lines in farmed aquatic animals. © 2010 Elsevier B.V. All rights reserved.

Hamzah A.,Universiti Sains Malaysia | Hamzah A.,National Prawn Fry Production and Research Center | Ponzoni R.W.,Worldfish Center | Nguyen N.H.,Worldfish Center | And 4 more authors.
Pertanika Journal of Tropical Agricultural Science | Year: 2014

A selective breeding programme of Nile tilapia (Oreochromis niloticus) based on a fully pedigreed population of the GIFT (Genetically Improved Farmed Tilapia) strain has been carried out using Best Linear Unbiased Prediction (BLUP) method for genetic evaluation and selection. Two lines were created from the 2002 progeny; one selected based on high breeding values (selection line) and another one was selected for average breeding values (control line) for live weight (LW). The estimate of heritability for live weight at harvest was 0.24 ± 0.031, indicating that there is still abundant genetic variation and scope for further genetic improvement. The accumulated response was 107% in the latest generation of 2011, averaging 11.9% per generation. It can be concluded that although the selection programme in the nucleus of the GIFT strain in Malaysia resulted in significant improvement in harvest weight, there still exists an abundant genetic variation thus providing the scope for further enhancement in performance of this population. © Universiti Putra Malaysia Press.

Khaw H.L.,Worldfish Center | Khaw H.L.,Wageningen University | Ponzoni R.W.,Worldfish Center | Hamzah A.,National Prawn Fry Production and Research Center | And 2 more authors.
Aquaculture | Year: 2012

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. © 2011 Elsevier B.V.

Ponzoni R.W.,Worldfish Center | Nguyen N.H.,Worldfish Center | Khaw H.L.,Worldfish Center | Hamzah A.,National Prawn Fry Production and Research Center | And 2 more authors.
Reviews in Aquaculture | Year: 2011

We mainly (but not exclusively) draw on research and development work carried out by The WorldFish Center (WorldFish). We review in detail the current state of development of a selection program that has had a main focus on growth rate and body traits. We also present some new, unpublished, information. There is evidence of sustained gains of 10-15% per generation over more than six generations. To date, these gains have not been accompanied by any undesirable correlated response. However, the prospects of altering sexual dimorphism and the shape of the fish appear to be very limited. We also examine the issue of an appropriate environment for selection. Not surprisingly, experimental evidence on genotype by environment interactions suggests that this is more likely to be of importance when the environments in question are markedly dissimilar. We argue that no universal guidelines can be prescribed with regard to the need for more than one selection program to cope with different production environments, but rather, each case should be examined in its own right. Finally, we discuss traits likely to be candidates for inclusion in future, more elaborate, breeding objectives for Nile tilapia (Oreochromis niloticus), comment on selection methods that may be implemented in the future and conclude by stressing the need to maintain an effective population size in selection lines to ensure their sustainability over time. © 2011 Blackwell Publishing Asia Pty Ltd.

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