Shadowfax is the last of an ancient breed of horses, a horse king. In the Lord of the Rings trilogy, what is the name of the horse or horses that were honored to play Shadowfax?
The principal horse, however, was another Andalusian stallion named Domero (bold is my emphasis, italic is McKellen's):
Gandalf of course isn't as sentimental as this Englishman, although I had him whispering to the chestnut Clyde who dropped him off at Bag End in the first film's opening scene. Gandalf's equine faith lies other than in the likes of Bill and Clyde. As he tells Pippin: "Shadowfax will have no harness. You do not ride Shadowfax: he is willing to carry you - or not. If he is willing, that is enough. It is then his business to see that you remain on his back, unless you jump off into the air." He is speaking of a marvel and Peter Jackson has cast a white 16 year old Andalusian stallion called Domero who, standing at 16 hands is more than up to the part, at least as far as looks are concerned. His alert ears pivot above his noble skull, his mane is thick and in no need of the false hair that some of the other horses, including Bill, wear in the film.
Unfortunately, Domero succumbed to melanoma in 2003.