1. Division of Animal Biotechnology, National Institute of Animal Science, Rural Development Administration, Suwon 441-706, Korea.
2. Department of Biological Science, Sungkyunkwan University, Suwon 440-746, Korea.
3. Division of Dairy Science, National Institute of Animal Science, Rural Development Administration, Suwon 441-706, Korea.
4. Department of Animal Science and Biotechnology, Chungnam National University, Daejeon 305-764, Korea.