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Thodesen J.,Akvaforsk | Rye M.,Akvaforsk | Wang Y.-X.,Hainan Progift Aqua Technology Co. | Bentsen H.B.,Nofima Marin. P.O. Box 5010 | Gjedrem T.,Akvaforsk
Aquaculture | Year: 2012

Genetic parameters and selection responses were obtained for fillet weight and fillet yield of Progift Nile tilapia (Oreochromis niloticus) in China after six generations of multi-trait selection for growth and fillet yield. A total of 9619 test fish representing 687 full-sib families in six generations (G 1-G 6) of Nile tilapia originating from the GIFT breed were sacrificed to record skin-on fillet weights. Some of these skin-on fillets were further processed by skinning (5971 test fish) and trimming (4633 test fish) to allow calculations of three estimates of fillet yield (based on skin-on, skinned and trimmed fillets). Recorded fillet weights were positively influenced by body weight and negatively influenced by age at recording. The heritability (h 2) of skin-on fillet weight showed large variation in magnitude between generations (range of 0.00-0.45), but was of medium magnitude (0.30) when analyzing all data combined. The h 2 of fillet yield, which varied between 0.08 and 0.30 in different generations, was relatively stable (0.17-0.23) for different estimates of fillet yield when analyzing across all generations. Including all data, the effects common to full-sibs (c 2) accounted for 8% and 1-2% of the total phenotypic variance, respectively, for skin-on fillet weight and different estimates of fillet yield. The genetic correlations between different estimates of fillet yield were all very high (0.95-0.97 when analyzing all data) showing that it is sufficient to select based on skin-on fillet yield. The genetic correlation between skin-on fillet weight and body weight at harvest was also very high (0.97), while that between fillet yield and fillet weight was of moderate magnitude (0.33). The genetic correlation between fillet yield and body weight at harvest was not significantly different from zero. Genetic trend analysis based on all data predicted accumulated selection responses of 121g (1.87 phenotypic standard deviation units) larger skin-on fillet weight and 1.2%-units higher skin-on fillet yield after six generations of multi-trait selection. It is concluded that the ongoing program in China has resulted in considerable genetic improvement of fillet weight, and that genetic changes of fillet yield is a much slower process (0.2%-units per generation). Implications for commercial selective breeding programs are discussed. © 2012 Elsevier B.V.


Thodesen Da-Yong Ma J.,Akvaforsk | Rye M.,Akvaforsk | Wang Y.-X.,Hainan Progift Aqua Technology Co. | Li S.-J.,Hainan Progift Aqua Technology Co. | And 2 more authors.
Aquaculture | Year: 2013

Genetic parameters and selection responses were obtained for growth, pond survival and cold-water tolerance of Progift blue tilapia (Oreochromis aureus) in China after four generations of multi-trait selection. Blue tilapia from four Chinese hatchery stocks and one from Vietnam were used to compose a synthetic breeding population. About 31,000 tagged fingerlings representing 519 full-sib families in five generations were tested in freshwater earthen ponds in Hainan Province of China. Individual body weights were recorded on 11,000 fish at the expected time of sexual maturation and 22,000 at harvest to estimate genetic parameters for growth rate. An additional 5000 tagged fingerlings representing all families in G3 and G4 were challenged to estimate genetic parameters for cold-water tolerance. Heritability (h2) estimates for body weight were relatively stable across time of recordings and generations, and was of similar magnitude (0.40±0.04) when analyzing all harvest data. The h2 of pond survival was considerably lower (0.05±0.01 and 0.08±0.11), while that of cold-water tolerance was intermediate (0.20±0.04 and 0.30±0.31) when estimated on the observed and underlying scales. Including all data, effects common to full-sibs other than additive genetic effects (c2) accounted for 7% and 1%, respectively, of the total phenotypic variance for body weight at harvest and the two survival traits. Genetic correlation between growth recorded at expected time of sexual maturation and at harvest was very high (0.99±0.01). The genetic correlation between growth and pond survival was positive (0.15±0.08), while that between growth and cold-water tolerance was not significantly different from zero (0.02±0.12). Breeding candidates in the base population (G0) were ranked according to their individual breeding values for growth (recorded as body weight at harvest), while those in later generations (G1-G3) were ranked according to a selection index including individual breeding values for growth and family breeding values for survival traits. A genetic trend analysis based on all grow-out data predicted an accumulated selection response of 168g (2.16 phenotypic standard deviation units) and an average selection response of 14.0% per generation of selection when using the LS mean of the G0 as a base line for the comparison. Genetic trend analyses of survival data predicted accumulated selection responses of 8.4 and 1.2%-units higher survival rates in earthen ponds and cold-water challenge tests, respectively. The average inbreeding coefficient (F) was estimated to be 2.1% in the G4 generation. The results are discussed in a practical context of adapting selective breeding technology to a new aquaculture species and it is concluded that the ongoing selective breeding of blue tilapia in China has resulted in considerable genetic improvements of both growth (about 70% larger body weight at harvest) and pond survival after four generations of multi-trait selection. © 2013 Elsevier B.V.


Thodesen J.,Akvaforsk | Rye M.,Akvaforsk | Wang Y.-X.,Hainan Progift Aqua Technology Co. | Li S.-J.,Hainan Progift Aqua Technology Co. | And 3 more authors.
Aquaculture | Year: 2013

Genetic parameters and selection responses were obtained for growth, survival and external color traits of Progift red tilapia (Oreochromis spp.) in China after four generations of multi-trait selection to increase all traits except black spots, which should, ideally, be eliminated from the breeding population. Red tilapia from four Asian and four South-American hatchery stocks were used to compose a synthetic breeding population. About 45,000 tagged fingerlings representing 610 full-sib families in five generations were tested in freshwater earthen ponds, freshwater floating cages and brackish water tanks in Hainan Province of China. About 30,000 fish were recorded at the expected time of sexual maturation (170days) and at harvest (250days) to estimate genetic parameters. Heritability (h2) estimate for body weight was 0.42±0.03 when analyzing all harvest data, while h2 of survival was 0.05±0.01 and 0.09±0.12, respectively, when estimated on the observed and underlying scales. The h2 of external color traits at harvest was 0.24±0.04, 0.51±0.03 and 0.14±0.02, respectively, for black spots, pigmented area and skin/scale color. Including all data, effects common to full-sibs other than additive genetic effects (c2) accounted for 3-5%, 2-3% and 5-13%, respectively, of the total phenotypic variance for body weight, survival and external color traits. Genetic correlations between observations at expected time of sexual maturation and at harvest were generally high in magnitude (0.9-1.0) for all recorded traits except black spots (0.78±0.06). The genetic correlation between growth in freshwater earthen ponds and floating cages was very high (0.92±0.06), while that between freshwater earthen ponds and brackish water tanks (0.33±0.14) suggests considerable genotype by environment interaction. The genetic correlation between growth and survival was favorable (0.42±0.11), while those between growth and black spots (0.28±0.09), pigmented area (-0.25±0.06) and skin/scale color (-0.09±0.07) were all unfavorable. Breeding candidates in G0-G3 were all ranked according to selection indices including individual breeding values for growth (recorded as body weight at harvest) and color traits, while those for G2 also included family breeding values for survival. A genetic trend analysis based on all grow-out data predicted an accumulated selection response of 175g larger harvest weight (2.13 phenotypic standard deviation units) and an average selection response relative to each parent generation of 12.3%, using the LS mean of the G0 as a base line for the comparison. Similar genetic trend analyses predicted accumulated selection responses of 5.0%-units higher survival rate, 0.6 scores less black spots, 0.9 scores larger pigmented area and 0.1 scores better skin/scale color on scales of 5, 6 and 6 scores, respectively. The average inbreeding coefficient (F) was 1.5% in the G4 generation. It is concluded that the ongoing selective breeding of red tilapia in China has resulted in considerable genetic improvements of growth (59% larger body weight at harvest), survival and external color traits after four generations of multi-trait selection. © 2013 Elsevier B.V.


Thodesen Da-Yong Ma J.,Akvaforsk | Rye M.,Akvaforsk | Wang Y.-X.,Hainan Progift Aqua Technology Co. | Yang K.-S.,Hainan Progift Aqua Technology Co. | And 2 more authors.
Aquaculture | Year: 2011

Genetic parameters and selection responses were obtained for growth of Progift Nile tilapia (Oreochromis niloticus) in China after six generations of multi-trait selection. About 64,000 tagged fingerlings representing 787 full-sib families in seven generations of Nile tilapia originating from the GIFT breed were tested in freshwater earthen ponds, floating cages in reservoirs and a brackish water earthen pond in Guangdong and Hainan Provinces of China. Individual body weight was recorded on 25,000 of these at the expected time of sexual maturation and 50,000 at harvest to estimate genetic parameters for growth rate. Heritability (h 2) estimates for body weight showed large variation in magnitude (0.00-0.52) when analyzing data from each test environment and generation separately. Estimates obtained in floating cages and a brackish water pond was comparable or lower in magnitude than those obtained in freshwater earthen ponds. The h 2 estimates for body weight at harvest became more stable (range 0.13-0.20) when data from previous generations were included in the analysis. Including all data, the effect common to full-sibs (c 2) accounted for 10% of the total phenotypic variance for body weight at harvest. Genetic correlation between growth recorded at expected time of sexual maturation and at harvest was 0.8, but seemed to decrease in later generations. The genetic correlations between growth in freshwater earthen ponds and other test environments were of similar magnitude. Breeding candidates in the base population (G 0) were ranked according to their individual breeding values for growth (recorded as body weight at harvest), while those in later generations (G 1-G 5) were ranked according to a selection index including individual breeding values for growth and family breeding values for fillet yield. The selection response for growth was, on average, 11.4% per generation of selection (range 7.4-18.7%) when estimated based on control groups representing the parental generations. A genetic trend analysis based on all data (h 2=0.20, c 2=0.10) predicted an accumulated selection response of more than 200g and an average selection response of 8.0% per generation of selection when using the LS mean of the G 0 as a base line for the comparison. The average inbreeding coefficient (F) was estimated to be 5.0% after six generations of selection. The results are discussed in a practical context of developing selective breeding programs for tilapias and it is concluded that the ongoing selective breeding of Nile tilapia in China has resulted in considerable genetic improvement of growth (60-90% larger body weight at harvest) after six generations of multi-trait selection. © 2011 Elsevier B.V.

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