A Feasibility Study on Sex Reversal of Nile Tilapia (Oreochromis niloticus) Fry using Different Doses of 17- Methyl Testosterone at Different Protein Levels

Abstract

This research was undertaken to investigate the effect of two protein diets (30% and 40%) and two hormonal doses 40 and 60 mg 17- methyl testosterone (MT)/ 1 kg diet on the sex reversal of Nile tilapia, Orechromis niloticus using validated microscopic examination of the gonads and sex determination of the fish. Nile Tilapia fry (seven days post hatching) receiving following diets for 28 days. Diet A - containing 30% CP (crude protein) without hormones as control 1; Diet B -40 mg MT with 30% CP; Diet C-60 mg MT with 30% CP; Diet D - containing 40% CP without hormones as control 2; Diet E- 40 mg MT with 40% CP; Diet F - 60 mg MT with 40% CP. The frequency data of males and females after treatment and microscopic characteristic showed that the % of males obtained by B (82% ), C (94%), E (92% ) and F (98% ) treatments were higher than the control groups (A and D), and a dose of 60 mg MT/1 kg of diet C and F were more efficient in sex reversal, resulting in 94 -98% males. Among diets, the treatment F (60 MT / kg and 40% CP) was better than the treatment C (60 mg MT with 30% CP). These results indicated that male sex reversal increase with increasing dose of MT and crude protein. The water quality parameters, recorded during the present study in rearing hapas such as Water Temperature (29- 35)°C,water pH(7.2- 8.5), Dissolved Oxygen content (3-.5.6)mg/L,Alkalinity (75-100) mg/L, Hardness (85-111) mg/L, and Ammonia(0.365-0.658) mg/L in the optimal water quality ranges for Nile tilapia. Results showed that fish growth was significantly affected by protein level and 17 methyl testosterone. The highest growth performance (final weight, and growth rate (GR) of fry were obtained with the 40% protein diet with 60 mg MT/kg.