THE EFFECTS OF α17-METHYLTESTOSTERONE ON SEX REVERSAL OF RED TILAPIA (OREOCHROMIS NILOTICUS X OREOCHROMIS MOSSAMBICUS) IN THE FREE-SWIMMING STAGE

The effects of 17α-Methyltestosterone (MT) on sex reversal of Red tilapia (Oreochromis niloticus x Oreochromis mossambicus) in the free-swimming stage by immersion and feeding techniques were studied at the Department of Fisheries, Faculty of Agricultural Technology, Rajamangala University of Technology Thanyaburi, Pathumthani Province from April to July 2017. The experimental design was a factorial experiment in CRD which studied two factors: 1) sex reversal by immersion treatment of 17α-MT (0, 150 and 300 μg/l) for 3 hours (T1, T2, and T3) and 2) sex reversal by feeding treatment of 17α-MT (40, 60 and 80 mg/kg) for 28 days (F1, F2 and F3). Results from these studies indicated that during the free-swimming stage, the immersion treatment of 17α-MT in 300 μg/l for 3 hours (T3) had the highest growth rate in terms of weight, total length (28 days), ADG, FCR and survival rate (0.731 g, 3.340 cm, 0.024 g/d, 0.627 and 95.443 % respectively). The immersion treatment of 17α-MT in 150 μg/l for 3 hours (T2) had a medial growth rate among the other factors. The immersion treatment of 17α-MT in 0 μg/l for 3 hours (T1) had a minimal growth rate but had the highest sex ratio of males (83 . 889 %). The effects on sex reversal by feeding treatment of 17α-MT in 60 mg/kg for 28 days (F2) had the highest growth rate in terms of weight, ADG and FCR (0.644 g, 0.022 g/d and 0.714 respectively). The effects on sex reversal by the feeding treatment of 17α-MT in 80 mg/kg for 28 days (F3) had a medial growth rate and the highest survival rate (95 . 037 %) and sex ratio of males (85 . 667 % 33T). The effects on sex reversal by feeding treatment of 17α-MT in 40 mg/kg for 28 days (FR1R) had a good growth rate but the other factors were minimal33T.