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12   |   Chapter 1
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                natural food.  Semi-intensive production systems are characterized by moderate                         for example, Genetically Improved Farmed Tilapia (GIFT) (Pullin et al., 1991; Eknath
                input use, pond fertilization using manures or inorganic fertilizers to boost natural                  et  al.,  1993; Bentsen  et  al., 1998)  and FaST(Bolivar, 1998), GenoMar Supreme
                food production,  use of supplementary homemade or commercial feed, higher                             Tilapia  (Zimmermann and Natividad, 2004) and GET-EXCEL  (Tayamen, 2004).
                stocking density than extensive production systems, and Nile tilapia can be farmed                     Among the Nile tilapia selective breeding programs, the GIFT breeding program is
                in monoculture or polyculture system. Earthen ponds without aeration are most                          the  most important non-commercial breeding  program. The  GIFT project  was
                commonly used in both extensive and semi-intensive production systems. Absence                         started in 1988 in the Philippines and executed by the International  Center  for
                of aeration results in recurrent high dissolved oxygen fluctuation during the day.                     Living Aquatic Resources Management (ICLARM), now WorldFish, in collaboration
                Nile tilapia requires a normoxic environment (dissolved oxygen above 5 mg/L) for                       with partner organizations (Pullin  et al., 1991). The base population was formed
                optimal  growth.  However, tilapia  are known to tolerate  dissolved oxygen levels,                    from four wild stocks from Egypt, Ghana, Senegal and Kenya and four commercial
                which often drop below 3 mg/L during nights.                                                           Nile tilapia strains farmed in the Philippines (Pullin et al., 1991; Gjedrem, 2012).
                                                                                                                       After six generations of selective breeding in the Philippines, WorldFish continued
                Intensive production systems are characterized by high  input  use, high  stocking                     the selective breeding of the GIFT strain in Kedah State, Malaysia, from generation
                density, use of a nutritionally complete pelleted diet, use of continuous aeration for                 six after receiving 63 full sib groups of 35 fish each from the Philippines towards the
                an optimized environment. Intensive Nile tilapia  production is practiced in                           end of 2000 and the beginning of 2001 (Ponzoni et al., 2011b). Currently, the GIFT
                raceways, cages and ponds. Extensive and semi-intensive production systems are                         strain has been selected for 20 generations in Malaysia and disseminated to more
                probably the dominant production systems, but exact numbers are not available.                         than 16 countries worldwide (Agha et al., 2018; WorldFish, 2021).
                Hereafter, both extensive  production systems and  semi-intensive production
                systems are referred to as smallholder production systems.                                             The Genetically Improved Farmed Tilapia (GIFT) breeding program benefited from
                                                                                                                       the experiences gained in salmon breeding  that started in 1971 in Norway
                                                                                                                       (Gjedrem, 2012).  Genetic gains in harvest  weight ranging  from 7-11%  per
                                                                                                                       generation over four to six  generations of  GIFT breeding  program  have been
                                                                                                                       published (Khaw et al., 2008; Ponzoni et al., 2011a; Thodesen et al., 2011). After six
                                                                                                                       generations of selection, the GIFT strain grew up to 85% faster than the fish used in
                                                                                                                       the base population (WorldFish, 2021).  The estimated selection response ranges
                                                                                                                       from 10  to 15%  in the last ten generations (Khaw,  2015).  Recently estimated
                                                                                                                       average selection response for GIFT  strain was 7% for 17 generations, indicating
                                                                                                                       continued response to selection (Benzie et al., 2021). Data from breeding programs
                                                                                                                       conducted with other Nile tilapia strains by WorldFish in Abbassa, Egypt, indicate
                                                                                                                       that on average 3%  selection responses have been achieved for 12  generations
                                                                                                                       (Benzie et al., 2021).

                                                                                                                       Other Nile tilapia selective breeding programs also reported considerable selection
                                                                                                                       responses. In China, on average 11.4% (range 7.4 to 18.7%) selection response was
                          Figure 1.1 World tilapia production from 1990 to 2019 (FAO, 2021).                           recorded for Progift Nile tilapia body weight (Thodesen et al., 2011). For GenoMar
                                                                                                                       Supreme  Tilapia  the average selection response over  11 generations  was  17%
                1.3.  Nile tilapia selective breeding programs                                                         (Gulzari, 2017).
                Many selective breeding  programs have been established for Nile tilapia.  Until
                2005, seventeen breeding programs were established for Nile tilapia (Neira, 2010),

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