1. Department of Veterinary Surgery; Obihiro University of Agriculture and Veterinary Medicine; Obihiro Hokkaido 080-8555 Japan
2. Department of Animal Reproduction; Obihiro University of Agriculture and Veterinary Medicine; Obihiro Hokkaido 080-8555 Japan
3. Veterinary Teaching Hospital; Obihiro University of Agriculture and Veterinary Medicine; Obihiro Hokkaido 080-8555 Japan
4. Department of Veterinary Internal Medicine, Faculty of Agriculture; Iwate University; Morioka Iwate 020-8550 Japan