This gruesome picture of a bull with two faces has become an internet sensation after the animal was sold at auction in Australia.

The photo of the mutant bull with its two faces and extra snout was posted to Facebook by farm workers in Mareeba, near Cairns, and has been shared thousands of times.

Yard chairman Gerry Collins said the deformity was due to a "genetic variation".

"Sometimes the genetic engineering doesn't quite work according to plan," he told the Brisbane Times.

But Collins said the animal was perfectly normal in every other respect and was able to digest its food.

He added it was not the first time he had noticed two-headed animals during his 30 years in the cattle industry.

"There was a fair bit of curiosity and interest but I don't know whether there was a lot of interest in a commercial sense," he said.

He would not comment on who had bought the bull.