1. Department of Animal Science, Chungbuk National University, Cheongju, Chungbuk 286-44, Republic of Korea.
2. Division of Animal and Dairy Science, Chungnam National University, Daejeon, Choongnam 341-34, Republic of Korea.
3. Department of Animal Resource and Science, Dankook University, Cheonan, Choongnam 311-16, Republic of Korea.