With the purpose of solving some practical problems concerning the complete masculinization
of Oreochromis niloticus by oral administration of 17a-methyltestosterone (17a-MT) with
respect to the dose of the hormone used, different doses of 17a-MT (40, 60 and 80 mg of 17a-
MT/kg of feed) were orally administered to sexually undifferentiated fries from the 7th to the
28th day posthatching to produce all male tilapia population