Sexual control through hormone treatments is widely used in Nile tilapia due to its simplicity and high efficiency. However, possible impacts of hormone residues introduced in the environment are still a topic of concern.
One way to minimize the environmental impact of hormonal treatments is to use close aquaculture systems, such as Biofloc Technology (BFT). However, BFT systems can provide constant additional feed and there is the possibility that the feed with masculinization hormone offered would not be fully ingested, resulting in a lower ratio of males in relation to the traditional hormonal inversion protocols. Hence, different feeding frequencies and hormonal concentrations, superior to conventional protocols of masculinization, should be tested.
A team of international researchers elaborated a masculinization protocol that would allow better growth and higher masculinization percentages for Nile tilapia in BFT. Nile tilapia fry were raised in BFT and submitted to different concentrations of 17α-methyltestosterone (60, 90, 120, 150 and 180 mg kg−1) which was offered five or eight times a day. The control group consisted of fry raised in clear water tanks fed with 60 mg kg−1 hormone diet provided five times a day.
Animals submitted to BFT systems presented higher survival and uniformity when compared to the clear water group. Higher hormone concentration treatments presented less proportion of males in contrast to 60 mg kg−1 groups and no differences were found between feed frequencies tested.
Researchers concluded that it is possible to achieve ≥94% masculinization rates in tilapia using 17α-methyltestosterone at 60 mg kg−1 on BFT systems, under a five times per day feeding regime.
Check out the study here.