LES KOSKLIN admits there were times when his promising four-year-old mare, Tuscan Abbe, showed the aggressive behaviour of a stallion, particularly when she was near other mares.

At first the harness racing trainer thought nothing of it. But then the horse won at Bankstown and a swab revealed elevated levels of testosterone.

Officials suspected doping and raided Kosklin's Newcastle stables in search of evidence. They found none and it was only when the pacer was given an internal examination by a reproductive specialist that the truth emerged.

Tuscan Abbe is a hermaphrodite: a female horse possessing a male Y chromosome and internal male testes that produce large amounts of testosterone known in racing circles as an intersex mare.

The case, which comes after revelations about South Africa's world champion 800-metre runner, Caster Semenya, has serious implications for Tuscan Abbe. It is likely she will no longer be able to compete in fillies and mares events.

''I actually said to the owners early on, she's a Ladyship Mile horse next year,'' said Kosklin. ''But we might have to change that to the Miracle Mile now.''

Reproductive vet Dr Cecelia Cortina Di Favria did an ultrasound and concluded something was amiss.

A DNA test confirmed the presence of a Y chromosome.

Kosklin believes Tuscan Abbe's testosterone levels are cyclical. A second swab was negative, but two weeks later its testosterone levels were ''through the roof''.

While it is rare, Tuscan Abbe's circumstances are not unique.

A Canadian standardbred called Arizona Helen was found this year with features of a male and female. There is also a horse in Victoria called What Am I - which has never raced exclusively against females in any of its 15 starts - that is also intersex.