Fish and Aquatic Conservation

17α-methyltestosterone INAD #11-236

Tilapia at a commercial farm.
Credit: USFWS


17α-methyltestosterone (MET) is an aquaculture premix and is only available through Rangen Inc. The primary goal of studies conducted under INAD #11-236 is to generate data evaluating the efficacy of MET administered in feed to larval tilapia to produce populations comprised of >90% male fish. The treatment option that is allowed is a dose of 9 mg active drug/kg of fish biomass. MET will be incorporated into tilapia feed by Rangen, Inc. at a rate of 60 mg MET/kg feed. Therefore, based on standardized procedures for tilapia production, newly hatched tilapia fry should be fed 150 g MET-medicated feed/kg fish biomass/day (i.e., fed at 15% body weight daily). MET-medicated feed should be fed to tilapia fry for 28 consecutive days. No retreatment will be allowed. Investigational Withdrawal requirements (days or individual fish weight) depend on whether fish are reared in a “batch culture” system (120-d Investigational withdrawal period) or a “partial-harvest/restock culture” system (individual fish must weigh at least 350 g before being taken to market).This INAD requires all participants to be approved by the FDA Environmental Team prior to participation – this review will take 90 days. To participate in the INAD Program for MET visit the data collecting site.

Please read the Study Protocol prior to any treatments. It contains the protocol, MSDS, and a copy of the forms to be used as a guide for collecting data that will be entered into the online INAD database. The FDA authorization letter(s) for this INAD is currently only available by emailing Bonnie Johnson .

INAD objective/purpose: Collect supportive and pivotal data needed to establish the effectiveness of 17-α methyltestosterone when fed as a feed additive to larval tilapia to produce populations comprising over 90% male fish.

Drug Name
17-α methyltestosterone (MET)

Drug Source
Rangen Inc.
P.O. Box 706
Buhl, ID 83316

Attention: David Brock
Phone: 1-800-657-6446 x ext. 1332
Fax: 208-543-8037

Target pathogen(s): Not Applicable

Method of administration: Medicated feed treatment

Treatment dosage:

  • 9 milligrams (mg) MET per kilogram (kg) fish per day
  • Note: MET will typically be incorporated into standard tilapia feed at a rate of 60 mg MET per kg feed; fish should be fed at 15% body weight per day.

Treatment regimen:

  • 28 consecutive days

Investigational Withdrawal period:

  • Batch Culture: 120 days (from last day of treatment).
         Note: Batch culture is defined as when all fish in a group/lot enter and leave the lot at the same time.
  • Partial Harvest/Restock Culture: individual minimum weight of 350 grams per fish.
         Note: Partial harvest/restock culture is defined as the mixing of different lots of fish during the grow-out period and selective harvest from the production unit at      various times.

Required test parameters:

  • Investigator needs to report general fish behavior and any adverse effects relating to treatment.

Limitations or restrictions on use of drug:

  • No re-treatment of fish is allowed. Investigator must follow all instructions in the Study Protocol for INAD 11-236 regarding drug acquisition and handling, fish treatment and disposition, and data reporting requirements. The FDA/CVM Environmental Team requires each facility to provide their MET effluent information to them prior to their participation under the INAD. Each facility that would like to participate under INAD #11-236 must provide the AADAP Office with written assurance that procedures and/or mitigations are in place to insure MET will not be released in effluents or leached to groundwater. Treated water cannot be used through grow out tanks or on fields where vegetation may be harvested for food. Therefore, each facility will need to send an email or letter to the AADAP Office describing how MET effluent from treated tanks is discharged and give assurance that zero MET is discharged into public surface waters. Please note you may want to include a diagram of your facility. The AADAP Office will then submit your facility's information to FDA/CVM's Environmental Team for approval to participate under this INAD. Note: this approval process usually takes 90 days so please plan accordingly.
  • Drug discharge must be in compliance with local NPDES permitting requirements.

Required INAD fee: $700/facility/year

AADAP Contact Information:
Ms. Bonnie Johnson, FWS-AADAP
Phone: 406-994-9905
Fax: 406-582-0242