The researchers said Monday that a brown and white calf named Millie, short for Millennium, was born full-term on Aug. 23, weighing 62 pounds. She is the third bovine cloned from adult cells born in the United States, but the first Jersey and the first using standard cell-culturing techniques.
"Cloning procedures are more simple than we first thought," said Dr. Lannett Edwards, who studied as a visiting U.S. Department of Agriculture scientist with researchers in Scotland who cloned Dolly in 1996. She led the effort here with her husband and colleague Dr. Neal Schrick.
The two other cloned cows born in the United States have been produced by researchers at Texas A&M and the University of Connecticut within the past year.
Using ultrasound technology, the Tennessee researchers collected ovarian cells from a cow named Teresa. Next, Edwards removed the DNA from the egg of another cow, leaving behind egg cytoplasm.
Edwards then joined one of the cultured cells from Teresa to the remaining egg cytoplasm, using a technique called electrofusion. The result was a one-cell cloned embryo that began developing with nuclear DNA entirely from Teresa.
Ninety-five embryos were cultured in the laboratory, allowed to mature for seven days, then transferred to 17 surrogate black Angus beef cows. Millie was among nine pregnancies that resulted and was born after 278 days. A normal pregnancy for Jerseys is 280 days.
The researchers said this was achieved without patented techniques to slow the development of the donor egg cells -- a so-called quiet state used in cloning two other cows in the United States and Dolly the sheep.
"We basically were able to use routine cell culture methods in the laboratory," which could make cloning on a commercial basis more affordable, Edwards said.
"It is significant just to see another lab produce another clone," said Jerry Yang, director of the Transgenic Animal Facility at the University of Connecticut, which cloned a cow using frozen ear cells of a prize Japanese bull. "It is very complicated technology."