(Photo: Sina.com)

    WASHINGTON, May 23 (Xinhuanet) -- Scientists said Sunday they have successfully conducted serial cloning or cloning of a clone of a large animal, which could be of great implications for animal breeding industry in the future.

    The scientists at the University of Connecticut and their Japanese colleagues have confirmed two live births of second generation clones of a famous Japanese breeding bull, according to a press release faxed to Xinhua.

    The second generation cloned bulls were actually born on Jan. 23, 2000, and March 6, 2000 separately. Although one of the two calves died of anemia and infection shortly after birth, the second has survived over four years in apparent good health, indistinguishable to peers from natural reproduction, the press release said.

    "The reason that we held off reporting this major achievement until now is that we wanted to be sure that the second generation bull clone could mature normally, and prove fertile with its health certain," said Dr. Xiangzhong (Jerry) Yang, professor and director of the University of Connecticut's Center for Regenerative Biology, who led this successful research team.

    "Only then we should claim our success," he added.

    A paper describing the somatic cell nuclear transfer cloning technique used to produce the second generation bull clones will appear in the May 23, 2004 issue of the journal"Nature Biotechnology."

    The research is the result of collaboration between the laboratories of Dr. Yang and Dr. Chikara Kubota of the Kogashima Cattle Breeding Development Institute in southern Japan.

    The surviving second-generation bull clone, was given the name "Sho-zaburo" (English name Dr. Lederman) to reflect the Chinese/Japanese culture in their dedication to this collaboration, which started about ten years ago.

    In 1998, Yang and Kubota, who previously worked and collaborated in the Yang laboratory at the University of Connecticut, successfully produced four cloned calves from the earskin cells of a genetically elite, 17-year-old Japanese Black bull,which had sired over 160,000 offspring in Japan.

    The production of these clones represented the world's first male clones of a farm animal, and was cited as "the largest clones in the world" by the Guinness World Records.

    Ear skin cells were collected from one of these cloned bulls for re-cloning and led to the birth of the world's first second-generation clone in a non-rodent species.

    Serial somatic cell cloning was initially reported in mice in 1998, but attempts around the globe to clone a clone (including Dolly) have failed.

    In their attempt, Yang's team manipulated 665 eggs and produced 358 cloned embryos. Nineteen embryos were transferred to19 recipients, which led to two live births of second-generation cloned bulls.

    The researchers reported that they attempted to produce third-generation clones from the same bull, but their efforts failed after implanting 30 cloned embryos in 30 recipient cows. Enditem