Residual levels of 17α-methyldihydrotestosterone in Nile tilapia (Oreochromis niloticus) fry following feeding supplementation

Abstract

Intensive tilapia culture requires male-monosex population for its better yield and allowing more effective management of a single crop. Androgenic hormones are usually applied during the fish farming process to produce male-monosex population. This study investigated the residue of a synthetic androgenic steroid, 17α-methyldihydrotestosterone (MDHT) after a course of feeding supplementation in Nile tilapia (Oreochromis niloticus) fry at a dose of 80 mg/kg feed for 15 and 23 consecutive days. An analytical method using liquid chromatography tandem mass spectrometry was developed to determine the residual MDHT in tilapia fry at 1, 2, 3, 5, 7, 14 and 21 days after the last dose. The levels of MDHT on day 1 after hormone withdrawal were 3.198 ng/g in the 15-day treatment, and 3.224 ng/g in the 23-day treatment. MDHT was not detectable in fry after hormonal withdrawal for 5 days in both treatments (limit of quantitation, 0.95 ng/g), which suggests that negligible levels of MDHT will be present in Nile tilapia after 6–8 months hormonal withdrawal during the grown out period.