KNOXVILLE, Tenn. (AP) _ The third cow cloned from adult cells born in the United States was found dead in a pasture and researchers don't know how it died.
Born nine months ago, Millie, short for millennium, also was the first clone of a Jersey cow, a top milk-producing breed, and the first using standard cell-culturing techniques.
Millie had been out in a pasture at the University of Tennessee's Experiment Station in Knoxville. She was found dead there early Monday.
Except for a slight variation in the size of one her kidneys, the cow showed no visible signs of abnormalities, said veterinary pathologists Philip Bochsler and Malcolm McCracken, who performed a necropsy.
``We don't know why she died,'' said Patricia Clark, a spokeswoman for the university's Institute of Agriculture.
Researchers were checking to see if the animal was the victim of a lightening strike or ingested a toxin, including poisonous weeds. No other animals at the station appeared to be affected.
``Other than the fact that we knew she was a clone, she was just like any other young cow,'' McCracken said. ``At this point, we cannot conclude why she died.''
Millie passed her last veterinary exam on April 30. ``She was healthy and fine and happy,'' Clark said.
``As far as the cloning procedures themselves, I doubt very seriously that it will change the program,'' Clark said. ``But it is a setback, no doubt.''
The first two cloned cows born in the United States were produced by researchers at Texas A&M and the University of Connecticut.
Researchers have said that cloning offers the cattle industry a possibility for increased reproduction from prized bulls, increased milk production and greater resistance to disease.