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Safety of Feed Treated with 17α‐Methyltestosterone (17MT) to Larval Nile Tilapia
Author(s) -
Straus David L.,
Bowker James D.,
Bowman Molly P.,
Carty Daniel G.,
Mitchell Andrew J.,
Farmer Bradley D.,
Ledbetter Cynthia K.
Publication year - 2013
Publication title -
north american journal of aquaculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 41
eISSN - 1548-8454
pISSN - 1522-2055
DOI - 10.1080/15222055.2012.758211
Subject(s) - nile tilapia , methyltestosterone , biology , oreochromis , tilapia , zoology , larva , gonad , aquaculture , fishery , aquaculture of tilapia , fish <actinopterygii> , toxicology , endocrinology , ecology
As a synthetic androgen, 17α‐methyltestosterone (17MT) is frequently used to redirect the course of sex differentiation by exposing the undifferentiated gonad to a sufficient dosage. This hormone has been widely accepted as a safe and effective treatment for sex reversal in many fish species, and it is administered to larval tilapia (3–12 d old) for ∼28 consecutive days to produce populations of >90% males. This study assessed the safety of 17MT‐treated feed when administered to larval Nile Tilapia Oreochromis niloticus at one, three, and five times (i.e., 1×, 3×, and 5×) the proposed dosage of 9 mg 17MT/kg fish daily for 28 consecutive days. Despite elevated total ammonia nitrogen levels measured during the last 5 d of the study, environmental conditions were acceptable for rearing tilapia. Fish fed aggressively regardless of the concentration of 17MT in the feed, behavior was considered normal with no dose‐related differences detected, and no mortality was observed in the 3× treatment group. Fish that were treated with five times the proposed therapeutic dosage had significant pathological changes. Based on the results of this study, the 17MT margin of safety extends to at least 3× (27 mg 17MT/kg fish daily) the proposed dosage of 9 mg 17MT/kg fish daily when administered in feed for 28 d to Nile Tilapia.