Masculinization, growth and survival of tilapia Oreochromis niloticus using natural and synthetic aromatase inhibitors

Tilapia masculinization using flavonoids

Abstract

The effect of natural and synthetic aromatase enzyme inhibitors on growth, survival, and masculinization in Nile tilapia offspring was evaluated. Five flavonoids: chrysin (CRI), 7-hydroxyflavone (7-HF), apigenin (NA), naringenin (NAR), and 7-methoxyflavone (7-MF) at 1 000, 1 500, and 2 000 mg kg^-1; a non-steroidal compound: letrozole (LT) at 50, 100, and 200 mg kg^-1; and two synthetic steroids: exemestane (EXE) at 1 000, 1 500, and 2 000 mg kg^-1, and 17 α-methyltestosterone (MT) at 60 mg kg^-1 (C+), with a negative control free of compounds (C-). Each treatment was conducted in triplicate with n = 30 fish per replicate (0.012 ± 0.01 g) in cylindrical tanks (6 L) with continuous flow at 28°C. The 7-HF groups at 1 000 and 2 000 mg kg^-1 showed significantly higher specific growth (16.08 ± 0.63% and 8.38 ± 2.11%, respectively). Survival was 100%, except for 7-HF 2,000 mg kg^-1, NA 1,500 mg kg^-1, 7-MF at 1 500 mg kg^-1, and EXE at 1 500 and 2 000 mg kg^-1, with 80 and 90%. The percentage of males in MT, EXE, and LT was 100%, but the flavonoid treatments varied, increasing from 57% males in C- to 71 to 86% for CRI 2 000, 7-HI 1 500, and all inclusion levels of 7-MET, NA, and NAR treatments. Further evaluation is expected to establish the concentration of natural inhibitors closer to 100% males.