Optimization of dose of methyl testosterone ( MT ) hormone for sex reversal in tilapia ( Oreochromis niloticus L . )

This paper describes the optimization of dose of methyltestosterone (MT) hormone for masculiniza ti on of ti la pia (Oreoclzromis nilolicus). Five treatments (i.e. T 1> T 2, T 3, T_1 and T 5) with different doses such as 0, 40, 50, 60 and 65 mg of MT hormone were mixed with per kg of feed for each treatment and fed the fry four times a day up Lo satiation for a period of 30 days. The stocking density was maintained 10 spawn/liter of waler. The growth of fry at different treatments was recorded weekly and mortality was recorded daily. AL the end of hormone feeding the fry were reared in hapas fixed in ponds for another 70 days and at the lOOth day the fish were sexed by the gonad squashing and aceto-carmine staining method. The analysis of growth data did not show any significant variation in length and weight of fish among the different treatments. High mortality of fry ranging 66% to 81.6% was observed in different treatments and highest mortality was observed during the first twelve days of the experiment. The sex ratio analysis showed that T 2 (40 mg/kg) and T, (65 mg/kg) produced 93.33% of sex reversed male and T 3 (50 mg/kg) and T 4 (60 mg/kg) produced 96.66% sex reversed male, and these ratios were significantly (p<0.05) different from 1:1 male: female sex ratio. The control, T 1 (0 mg/kg) contained 43.33% male progeny. From these results it is suggested that either 50 mg/kg or 60 mg/kg of MT with a feeding period of 30 days could be considered as an optimum dose for masculinization of tilapia (0. niloticus).