Hormonal Masculinization and Growth Performance in Nile Tilapia (Oreochromis niloticus) by Androgen Administration at Different Dietary Protein Levels

The study was planed to determine the effects of different doses of hormone 17a-methyltestosterone (MT) and different protein level of feeding on masculinization and growth performance in Nile tilapia (Oreochromis niloticus). The experiment was conducted in two phases. In phase-I, two experiments were performed in six glass aquaria with two replicates. In each aquarium, 50 fry of tilapia were stocked. In experiment A, three glass aquaria were used having the size of 3.0 x 1.5 x 1.0 ft. In this experiment, aquarium -1 was used as control (no hormone given) while in aquaria-2 and 3, the MT were given@ 60 and 70 mg MT/kg of feed containing 30% crude protein. In experiment B, aquarium - 4 was used as control (no hormone added) while in aquaria-5 and 6, the MT were given@ 60 and 70 mg MT/kg of feed containing 40% crude protein. Both the experiments were run parallel for 30 days. In phase-II, the fry were shifted to 6 earthen ponds in which feed was given without hormones on the same protein level as in phase-1, to monitor their growth performance for 183 days. At the final harvest frequency of males and females was determined by morphomatric characteristics and examination of gonads. Results showed that MT treated groups had significantly higher number of males than control and maximum fish growth was recorded in treatments fed with 40% CP level as compared to 30% CP level. The highest percentage of male (93-100%) was recorded at the hormone dose of 70 mg MT/kg of feed with 30 and 40% protein levels. Masculinized tilapia showed maximum growth performance (final body weight 162.4 g & weight gain 160.4 g) with maximum fish production i.e., 2000.7 kg/ha/year at 40% CP diet with 70 mg MT/kg of feed. Among all the sexes (male, female & inter sex), females showed the highest gonadosomatic index (GSI), which was lowest in males. In conclusion, higher hormonal dose and higher dietary protein level increased masculinization and growth in fish. © 2010 Friends Science Publishers