A racehorse in Sydney, Australia, has been revealed to be a hermaphrodite or intersex mare.

Trainer Les Kosklin told local newspapers that, following a convincing win in a harness race at Bankstown, a swab test on the promising four-year-old had detected elevated levels of testosterone.

Racing stewards asked the Newcastle Equine Centre to examine the mare and officials raided Mr Kosklin’s Newcastle stables in search of evidence of doping.

A reproductive specialist confirmed the mare, Tuscan Abbe, had internal testes, which were producing the large amounts of testosterone and the presence of a male Y chromosome.

“The mare doesn’t look like she has a uterus, and potentially has two testicles inside her abdomen,” explained Dr Patrick Kelly of Newcastle Equine Centre.

“We can’t be sure they are testicles, we assume they are because they are the right size, right consistency and are in the right place…they are certainly not ovaries.”

Mr Kosklin, who says the mare sometimes shows aggressive stallion-like behaviour, believes that her testosterone levels are cyclical.

And this seems to be borne out by a second veterinary swab that was negative for testosterone, whereas one taken two weeks later showed substantially elevated levels.

After the win at Bankstown, Tuscan Abbe won the $10 000 Sires Stakes race for fillies, and was placed third in the Sires Stakes Final at Harold Park, collecting another $10 000.

But the revelations about her gender have put her future racing career in question as it is unlikely that she will be allowed to compete in mares events.

Although rare, there have been other cases of intersex horses.

In Victoria, Australia, there is an intersex racehorse, fittingly named What Am I, which has never raced exclusively against females.

And earlier this year the Canadian standard-bred Arizona Helen was discovered to have the anatomical features of a male and a female.