"
The animal has been particularly sprightly and her death was very unexpected
"
Rob Lewis, South Australian Research and Development Institute
An autopsy failed to find any reason for the merino ewe's abrupt death last Saturday, Rob Lewis, director of the South Australian Research and Development institute, said.
The cremation of the carcass triggered criticism among opponents of cloning, who said that there would be no further opportunity to determine what killed Matilda.
Matilda was born in April 2000 from cloned embryos using a similar technology to that used to produce the world's first cloned sheep, Dolly, in Scotland in 1996.
'Unexpected death'
Mr Lewis said that Matilda died on Saturday at the research institute near the southern city of Adelaide, but her decomposing carcass was only found the next day.
"
Animal's don't die and decompose in five minutes. That's not really very plausible
"
Bob Phelps, Gene Ethics Network
"The animal has been particularly sprightly and her death was very unexpected," he said.
"There was nothing that was grossly obvious in the organs and outer body. The body's been cremated because it was in a very bad state. To be honest, it was clearly pongy, very pongy."
Mr Lewis said Matilda's death was a blow for the institute's efforts to produce rare sheep with outstanding genes to boost meat and fleece production.
"She was the one that provided the confidence to our science community that we could do this technology. She was the one that gave us standing internationally."
But Mr Lewis said the programme would continue.
Critics of cloning and gene technology said the institute should have made greater efforts in establishing the exact cause of death.
"Animal's don't die and decompose in five minutes," said Bob Phelps of Australia's Gene Ethics Network.
"That's not really very plausible."