|BOWMAN, MOLLY - Us Fish And Wildlife Service|
|BOWKER, JIM - Us Fish And Wildlife Service|
|CARTY, DANIEL - Us Fish And Wildlife Service|
|Straus, David - Dave|
|Ledbetter, Cynthia - Cindy|
Submitted to: Aquatic Animal Drug Approval Partnership (AADAP)
Publication Type: Other
Publication Acceptance Date: 2/1/2012
Publication Date: 2/17/2012
Citation: Bowman, M.P., Bowker, J., Carty, D.G., Straus, D.L., Farmer, B.D., Mitchell, A.J., Ledbetter, C.K. 2012. The safety of 17a-methyltestosterone administered in feed to larval Nile tilapia. Aquatic Animal Drug Approval Partnership (AADAP). Drug Research Information Bulletin (DRIB) 28. 3 p.
Technical Abstract: Techniques developed to control sexual differentiation in fishes have typically involved androgen or estrogen (i.e., steroid) treatment, which directs sexual differentiation toward males or females. Treatment regimens have included immersion of larval fish in water containing a steroid, incorporation of a steroid in the larval diet, or both. Gonadal differentiation in tilapia (Oreochromis spp.) occurs at 8-25 d post-hatch, and these fish begin to reproduce at 3-6 months of age. Such early reproduction is the primary impediment to their commercial production. To prevent reproduction from occurring, oral administration of the synthetic androgen 17a-methyltestosterone (17MT) to newly hatched tilapia (3-12 days old) for approximately 28 consecutive days produces populations of >90% males. We conducted a study to estimate a margin of safety associated with administering 17MT-treated feed to larval Nile tilapia O. niloticus at 0x, 1x, 3x, or 5x the proposed maximum efficacious dosage of 9 mg 17MT per kg fish body weight per day) for 28 consecutive days. We concluded the margin of safety associated with administering 17MT-treated feed to larval Nile tilapia reared at a water temperature of approximately 28 degrees C extends to at least 3x the recommended dose.