1. Department of Animal Science & Biotechnology, Chungnam National University, Daejeon 305-764, Republic of Korea
2. National Livestock Research Institute, Rural Development Administration, Suwon 441-350, Republic of Korea
3. Department of Agricultural Science, Korea National Open University, Seoul 110-791, Republic of Korea
4. Department of Animal Science & Technology, Sunchon National University, Suncheon 540-950, Republic of Korea