The horse's name is Koha (meaning "gift" in Maori) and was donated by the New Zealand's Government, as a token of friendship. The "sacred horse" designation means that he is used in the shrine ceremonies (and he is the only sacred horse from abroad in a Japanese shrine).
Travel tip: If you wish to see Koha, you have to visit Shinkyu-Sha between 10am and 2pm, since the rest of the time he is kept in a different, modern stable.
EXIF info:
Nikon D80
Lens: VR 18-55mm F/3.5-5.6G
Focal Length: 18mm
Aperture: F/5.6
Shutter Speed: 1/100s
ISO Sensitivity: ISO 100