Scienceline Publications World’s Veterinary Journal 2322-4568 2 2 2012 June Growth Performance, Proximate Muscle Composition and Dress-Out Percentage of Nile Tilapia (Oreochromis niloticus), Blue Tilapia (Oreochromis aureus) and their Interspecific Hybrid (♂ O. aureus X ♀ O. niloticus) Cultured in Semi-Intensive Culture System 17 22 http://wvj.science-line.com/attachments/article/13/World's%20Vet.%20J.%202(2)%2017-22,%202012.pdf EN Waleed N. El-Hawarry Department of Animal Husbandry, Faculty of Veterinary Medicine, Alexandria University, Egypt O. niloticus and O. aureus and their interspecific hybrid (♂ O. aureus x ♀ O. niloticus), frys were produced in early September 2008 from a mass spawning of brooders in earthen spawning ponds. Frys for each genotype were nursed and overwintered in deep nursery ponds. Thereafter; six earthen growout ponds were used for communal stocking of each genotype (two replicates genotype-1). The growth performance of purebred O. niloticus, O. aureus and their interspecific hybrid (♂O. aureus x ♀O. niloticus) were studied. The highest records of final body weight (FBW), average daily gain (ADG, g fish-1 day-1), specific growth rate (SGR, % day-1), total fish yield (TFY, kg feddan-1 day-1) and net fish yield (NFY, kg feddan-1 day-1) were achieved by interspecific hybrid (♂O. aureus x ♀O. niloticus) compared with the other purebred genotypes of tilapia. O. niloticus, O. aureus and their hybrids reached 237.81±36.65g, 142.97±11.45g, 281.23±45.52 g, respectively, at the end of a 112 day culture period. Both purebred genotypes and their interspecific hybrid had similar moisture, crude protein content and crude lipid content; however; it should be noted that value of the crude lipid content was lower in the interspecific hybrid (♂O. aureus x ♀O. niloticus) than in purebred genotypes. Meanwhile, the hybrid dress-out% was intermediate to the purebred parental genotypes. These advantages of hybrid (♂O. aureus x ♀O. niloticus) together with its characteristics for salinity, cold tolerance and disease resistance as reported in previous works are highly indicative for the commercialization of hybrid tilapia farming in Egypt. It should also pointed out that it is not an intention to promote hybridization as the only method of genetic improvement, but simply as one method of improvement that has potential for some immediate gains. Desirable traits can usually be passed to the hybrid in one generation but it should be appreciated that hybridization can be a hit and miss proposition. Additionally; it may be desirable to backcross to either parental line or to breed the hybrids together and then select the best animals, thus combining hybridization and selective breeding. Purebred Oreochromis niloticus Oreochromis aureus Inter-Specific Hybrid Tilapia Growth Production Traits