She is the third bovine cloned from adult cells to be born in the United States but the first copy to be made of a Jersey cow.

US researchers say she was cloned using a quicker and less complicated method than that used to create Dolly the sheep.

The brown and white calf, whose name Millie is short for Millennium, was born on 23 August.

"Cloning procedures are more simple than we first thought," said Dr Lannett Edwards, who led the research team at the University of Tennessee.

Nevertheless, the success rate of cloning experiments remains extremely low. Millie was born after 95 cloning attempts.

It took 277 attempts to produce Dolly the sheep, and the Tennessee researchers hope to improve on their success rate in future experiments.