Effect of 17α-methyl testosterone, tamoxifen, and letrozole on growth performance and sex reversal of rainbow trout (Oncorhynchus mykiss)


Artemia and Aquaculture Research Institute, Urmia University, Urmia, Iran.



Sex reversal and producing a monosex population is one of the most preferred growth promotion techniques of rainbow trout culture. Thus, the effects of 17α-methyltestosterone (2 mg/kg), tamoxifen (2, 20, and 100 mg/kg), letrozole (2, 20, and 100 mg/kg), and a combination of tamoxifen (100 mg/kg) and letrozole (100 mg/kg) on growth, masculinization and serum steroid content of rainbow trout were investigated in this research. Ethanol-dissolved chemicals were sprayed on commercial trout diet, and ethanol was evaporated overnight. The fish were fed the treated diet for two months and afterward, they were fed a commercial diet for six months. Results showed that 17α-methyltestosterone reversed the sex of rainbow trout effectively. The proportion of males, intersex, and females in this group were 76.67%, 10%, and 13.33%, respectively. In contrast with 17α-methyltestosterone, using tamoxifen and letrozole showed no effect on sex reversal of rainbow trout. Growth performance was adversely affected by all chemical-treated diets. However, compensatory growth occurred during first month after ending treatment period.