Title: The safety of 17a-Methyltestosterone medicated feed to tilapia Authors
Submitted to: Annual Drug Approval Coodination Workshop
Publication Type: Abstract Only
Publication Acceptance Date: June 30, 2010
Publication Date: August 3, 2010
Citation: Straus, D.L., Bowker, J., Bowman, M., Carty, D., Mitchell, A.J., Farmer, B.D. 2010. The safety of 17a-Methyltestosterone medicated feed to tilapia [abstract]. Annual Drug Approval Coodination Workshop. 16:123-130. Technical Abstract: 17a-Methyltestosterone (17MT) is used in U.S. aquaculture under an Investigational New Animal Drug exemption to produce male populations of tilapia. Efforts to gain FDA-approval include this Target Animal Safety study. A study was designed to determine its histological safety to tilapia when fed at the therapeutic rate of 9 mg 17MT/kg body weight/day, and at 3 and 5 times this rate, for 28 consecutive days. Five day old tilapia fry were randomly stocked into 20 tanks at the rate of 50 fish per tank. There were 4 replications of each treatment (0, 9, 27, and 45 mg 17MT/kg body weight/day), and 4 surrogate tanks. The surrogate tanks were used to determine fish weights at weekly intervals to calculate the proper feeding rate. Glass aquaria contained 15 L of well water which was recirculated with an outside biological filter to oxidize ammonia. Water temperature and dissolved oxygen were measured daily and pH, alkalinity and hardness levels were recorded weekly. Total ammonia and nitrite-nitrogen were measured two times each week. Medicated feed was top-coated with 17MT and fed at 15% body weight/day; feed was offered 4 times daily. After the acclimation period, fish were fed their respective diets for 28 consecutive days. Fish were monitored for feeding activity, mortality, and morbidity. There were few mortalities and fish ate all feed offered. Gross pathology and histopathological examinations will be discussed.