A comparative study of growth and feed utilization efficiency of sex-reversed diploid and triploid Nile tilapia, Oreochromis niloticus L.

Growth performance, survival and feed utilization of diploid (2n) and triploid (3n) sex-reversed male and female Nile tilapia were evaluated at maintenance feeding (1% body weight (BW) day(-1)), fixed feeding (3% BW day(-1)) and apparent satiation feeding levels in a freshwater recirculation system comprised of thirty-six 1-m(3) concrete tanks at the Asian Institute of Technology, Bangkok, Thailand. Triploid Nile tilapia (3n) was produced by subjecting fertilized diploid (2n) tilapia eggs to heat shock. After hatching, fish were sex-reversed to all-male and all-female populations by oral administration of 17 alpha-methyltestosterone (60 mg kg(-1) feed) and ethynylestradiol (100 mg kg(-1) feed) respectively. There was significantly higher growth with increased ration levels in both male and female groups. There were no significant differences in final BW, specific growth rate, survival rate, feed conversion ratio and protein efficiency ratio between diploid and triploid fish. Triploids had lower gonad weights than diploids, and this was particularly evident at the satiation feeding level. Triploid fish had a significantly higher apparent net protein utilization and percentage of gutted weight than diploids at all feeding levels. Higher protein utilization efficiency of triploids might be an advantage for commercial tilapia culture but further research is necessary to make such a conclusion.