Efficacy of trenbolone acetate in sex inversion of the blue tilapia Oreochromis aureus

Trenbolone acetate (TEA) is a synthetic anabolic androgenic steroid approved in the United States as a growth promoter for beef cattle. Pooled populations of blue tilapia Oreochromis aureus with more than 98% males were produced by feeding diets containing TEA. This hormone effectively inversed the sex of blue tilapia when doses of 25-100 mg/kg of diet were fed for 28 d. Fish treated with 60 mg of 17-alpha-methyltestosterone (MT)/kg of feed resulted in 88.7% males. The percentage of male tilapia masculinized with TEA was significantly higher (P <0.05) than with MT. Intersex fish were found in both control and hormone-treated groups, and were significantly more common (P <0.05) in the MT-treated batches. Survival, feed conversion ratio, and average weight of O. aureus fry fed diets containing either TEA, MT or no hormone were not different (P >0.05) at the end of the 28-d treatment period.