1. Department of Animal Breeding and Reproduction, National Institute of Livestock and Grassland Science, Ibaraki, Japan
2. Shimane Prefectural Animal Husbandry Experiment Station, Shimane, Japan
3. Ibaraki Livestock Research Center, Ibaraki, Japan
4. Koibuchi College of Agriculture, Ibaraki, Japan
5. National Agricultural Research Center for Tohoku Region, Iwate, Japan
6. Developmental Biology Department, National Institute of Agrobiological Sciences, Ibaraki, Japan