Elise Worthington reported this story on Wednesday, April 1, 2015 18:30:00

MARK COLVIN: New research has raised questions about a potent androgenic steroid used to beef up Australian cattle.



It's called trenbolone, and it's been banned in the European Union for decades.



Last year it was at the centre of an international trade dispute when Russia claimed it found traces of the chemical in Australian meat, and blocked exports.



The new research shows that trenbolone can cause male guppies to mate forcibly with unconsenting female guppies.



Scientists say that could have serious ecological and population effects.



Elise Worthington reports.



ELISE WORTHINGTON: In a small lab at Melbourne's Monash University, PhD student Michael Bertram has spent weeks watching guppies mate.



MICHAEL BERTRAM: They'll either dance for the female, which involves the male sort of presenting himself in front of the female. So it will flash in front of her, and then sort of contort his body into an S shape.



He'll flick in front of her and display his colours, and then if she's receptive - it's quite nice to watch actually - she will glide through the water and then he will come and fertilise her.



ELISE WORTHINGTON: Mr Bertram was part of a team from Monash and Åbo Akademi University in Finland studying the effects of a potent androgenic steroid called trenbolone, which is used to increase muscle mass in cattle.



The group used extremely low concentrations of the chemical to mimic the levels caused by naturally occurring run-off and filmed the guppies’ reaction.



As they reviewed dozens of hours of footage, they noticed the male guppies exposed to trenbolone became less likely to attempt to impress the females.



MICHAEL BERTRAM: They will actually instead favour what we call a sneaking behaviour, which involves the male sneaking up behind the female and copulating with her without first performing courtship.



The male actually insert a modified anal fin, which serves as a sort of sperm transfer organ. This is how they circumvent female choice in the sense that she doesn't get to first see the males and decide who she wants to mate with. She is just mated with.



ELISE WORTHINGTON: Co-author, Associate Professor Bob Wong, says it's not yet known exactly why exposed fish exhibited forceful mating behaviour, but there could be serious consequences.



BOB WONG: So, we know that sexual selection operating through processes such as mate choice can play a very important role in determining the number and also the quality of offspring that are produced.



And in turn, influence population dynamics, and that in turn can affect ecological and evolutionary processes.



ELISE WORTHINGTON: Trenbolone is an endocrine-disrupting chemical that has been banned in the European Union since 1988, but is widely used in beef production in Australia, the United States, South America, Japan and New Zealand.



In Australia, trenbolone is the most commonly used steroid in the 40 per cent of adult cows who are injected with drugs to promote growth.



Dr Wong says researchers studied the effect of the hormone on guppies because the results can translate into other small species.



BOB WONG: The amount of sperm that males can actually, I guess, give to the females. In the cases of the sneak copulations are usually much less than in matings that have the female's consent.



ELISE WORTHINGTON: Last year, Russia suspended imports of Australian beef after it detected traces of trenbolone in meat samples.



An Australian Department of Agriculture review found no evidence of the hormone, but the ban has remained.



A 2003 review by the Australian Pesticides and Veterinary Medicines Authority concluded there was unlikely to be any health risk to consumers from trenbolone or other growth promotants.



Mr Bertram says he's hoping this study will prompt further research and investigation by the authority.



MICHAEL BERTRAM: I expect the attention that this study will receive might mean that it's put on that watch list. And it's great to have something like that that means we can monitor the use of these chemicals.



ELISE WORTHINGTON: Meat and Livestock Australia and the Cattle Council of Australia have been contacted for comment.



The study was published in the international journal Hormones and Behaviour.



MARK COLVIN: Elise Worthington.