Efficacy of Gokshura (Tribulus terrestris) on Sex Reversal and Growth Performance of the Nile Tilapia (Orechromis niloticus) Fries Reared in Prolonged Water Exchange

          A total of 2000 fries of the Nile tilapia (Oreochromis niloticus) were obtained from private hatcheries to study the hormonal or gokshura extract and powder treatments on growth and sex reversal ratio under prolonged water exchange conditions. The 100-day experiment was applied using a completely randomized design. Fries were distributed in eight fiberglass tanks, with a volume of  1.5 m³, fitting for a stocking density of 250 fries/ tank. The initial average weight was recorded as 24.25± 12.65 mg/ fry. The experiment was divided into two stages, the first one (Sex reversal) lasted for 28 days, while the second (Sex differentiation) extended for 72 days. Four experimental treatments were conducted as follows: T₁ was considered as the control diet without any addition; T₂; a diet with the addition of 100mg of 17α-methyltestosterone hormone/ kg of diet; T₃ formed the diet supplemented with 200g/kg of Tribulus terrestris plant powder, and T₄ diet which contained 2g/ kg extraction of Tribulus terrestris plant. Feeding for all experimental treatments with hormone and plant (extract and powder) lasted for a period of 28 days concerning the first stage, with a diet containing 40% of crude protein, followed by a seventy-two- day rearing, during which fish samples were fed on a diet containing 30% of crude protein without any addition. The results showed that T₄ gave the best performance, feed conversion ratio and survival rate, followed by T₃. However, less performance was obtained for T₂ and control. The highest male percentage was recorded for hormonal treatment (T₂), followed by T₄, T₃ and control. The results of sex reversal ratio for the Nile tilapia fries revealed that the use of 2g/ kg diet extract of Tribulus terrestris (T₄) showed no significant difference with the hormonal treatment using 17α-MT (T₂). The present results proved that the use of 2g/kg extract of Tribulus terrestris is an eco-friendly, safe and economical aquaculture technique replacing synthetic hormones in commercial hatcheries.