Cloned calves at the double

The two cloned calves have not yet been named

Scientists in Japan say they have succeeded in cloning a cow.

The researchers at the Ishikawa Prefecture Livestock Research Centre said two cloned calves were born on Sunday, exactly two years after the birth in Scotland of Dolly the sheep, the world's first mammal copied from the genetic material in an adult cell.

The calves were born more than a month premature and were about 40% underweight at about 17 and 18kg each, but scientists in charge of the research say the animals are in good condition.

Experts said it proved that Dolly was not just a one-off.

They said by cloning adult cows with particular qualities, scientists could begin developing herds to produce more milk or better beef.

Dolly: The mammal cloned from an adult cell

The BBC's Toyko correspondent, Juliet Hindell, says the Japanese have in recent years acquired a taste for beef and milk - they eat a lot more of it than they did traditionally.

She also noted that the innovation could make it cheaper to breed cattle in countries where food is short.

Japan has banned research into cloning human beings but is promoting the cloning of livestock.

The Japanese scientists said they placed cells from an adult animal into unfertilised eggs whose nuclei had been removed.

They then fused them using small electric jolts to produce embryos that were later implanted into the wombs of surrogate cows.

In all, five cows were implanted with artificially cultivated embryos.

Four other cows are due to give birth to calves next month.