1. Department of Animal Science & Technology and BET Research Institute, School of Bioresource & Bioscience, Chung-Ang University, Gyeonggi-Do 456-756, Korea
2. Dairy Cattle Improvement Center, National Agricultural Co-operative Federation, Gyeonggi-Do 412-030, Korea
3. National Institute of Animal Science, Rural Development Association, Kangwon-Do 232-950, Korea
4. Department of Animal Sciences, The Ohio State University, OH 43210, USA