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This study evaluated the effects of various temperatures on growth of 17 alpha Methyl Testosterone treated Nile tilapia (Oreochromis niloticus) fry in Western Kenya. Nile tilapia larvae of Lake Victoria strain which had just hatched were subjected to different temperatures and Hormone concentrations in 40L aquariums in a 4 x 3 x 3 factorial experiment set up in a complete randomized design. The fry were fed on 10% body weight rations over a period of (28, 34 or 40 days) at 0800 hours, 1100 hours, 1400 hours and 1700 hours with equal amounts of the MT treated feeds. This paper reports an increase in growth of fry with increasing temperature (p<0.05) whereas MT concentration did not affect growth (p>0.05). The study showed that 60 mg MT/kg feed for 28 days at 30 0C are the optimal conditions for growth of Oreochromis niloticus fry grown by hatchery farmers in western Kenya.
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... In the study optimum growth for tilapia temperature is achieved at 30 to 31.5°C. The study by Odinga et al. [32] also showed that 60 mg MT/kg feed for 28 days at 30°C are the optimal conditions for growth of Oreochromis niloticus fry grown by hatchery farmers in western Kenya. Water pH and temperature were in optimum ranges for tilapia growth [25]. ...
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With the purpose of solving some practical problems concerning the complete masculinization of Oreochromis niloticus by oral administration of 17α-methyltestosterone (17α-MT) with respect to the dose of the hormone used, different doses of 17α-MT (40, 60 and 80 mg of 17α-MT/kg of feed) were orally administered to sexually undifferentiated fries from the 7th to the 28th day posthatching to produce all male tilapia population.After 15, 35 and 75 days and 1 year of treatment, growth parameters, survival rate, sex ratio and gonad histology of the resulting larvae and fish were demonstrated. The results showed that the highest survival rates of the fry were recorded in the group treated with 60 mg of 17α-MT/kg of feed compared to the control group, 40 and 80 mg of 17α-MT/kg of feed treated groups. The maximum sex ratios of males (95% and 97%) were recorded at 60 mg of 17α-MT/kg of diet after 75 days and one year of treatment respectively.After the first year, the degree of sex stability was observed significantly shifted towards males. The histological examination showed that the treatment caused an increase in male gonad recrudescence in most of the treated fish. In presumed genetic females, there are oocytes of young stages, gonial germ cells and different stages of degenerating oocytes within the period around 35 days posthatching.The present results concluded that 17α-MT has a potential effect in directing gonadal sex differentiation of OreochromisOreochromis niloticus towards males according to the dose involved in the treatment.
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