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Genetic improvement of Nile Tilapia in brackish water in Vietnam
Conference presentation

Genetic improvement of Nile Tilapia in brackish water in Vietnam

Thoa Ngo Phu
USC Research Conference, 2013 (Sunshine Coast, Australia, 01-Jul-2013–05-Jul-2013)
University of the Sunshine Coast
2013
url
https://www.usc.edu.au/View
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Abstract

Genetics Tilapia Vietnam
Shortage of freshwater presents a key problem to aquaculture in many countries including Vietnam. The present study aimed to develop a genetically improved strain of Nile tilapia for brackish water systems (10 - 20 ppt) in Vietnam. The synthetic base population was formed in 2007 from the best performing individuals produced from a complete diallel cross involving three strains of Nile tilapia, namely GIFT (Genetically Improved Farmed Tilapia), Taiwan and NOVIT4 (GIFTderived) strains. Selection was practised for increased harvest weight over four generations from 2008 to 2011. A total of 12,006 individuals had performance data records. They were offspring of 341 sires and 450 dams. Mixed model fitted to the data included the fixed effects of generation, sex, their two way interaction and a linear covariate of age nested within sex and generation, and the random effects of sire and dam. The estimates of heritability for body traits and survival were moderate to high (0.39 to 0.61). Genetic correlations between harvest weight and body length were high and positive (0.97), whereas those between body traits and survival were low and negative (-0.06 to -0.15). Genetic gain was measured as estimated breeding values and was expressed in actual unit (original scale of measurement) and genetic standard deviation unit (õG). The improvement achieved for harvest weight ranged from 1.1 to 1.6 õG after four generations of selection (or about 7% per generation). The improvement in harvest weight was however accompanied by a decrease in survival by -0.16õG. Our selective breeding significantly increased production performance of the fish in brackish water systems, but the future genetic program should account for survival in the breeding objective. The large genetic variation in both harvest weight and survival suggest that there is the prospect for simultaneous improvement of both traits in this population of Nile tilapia.

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