In the films, Shadowfax was portrayed by Andalusian stallions Blanco and Demero, adding to the majestic depiction of this legendary steed.
Shadowfax, a descendant of Felaróf and chieftain of the Mearas, the finest horses in Middle-earth, was an exceptional horse known for his intelligence, speed, and silvery-grey coat. Originally belonging to Théoden, King of Rohan, Shadowfax was too wild for the Rohirrim to tame. Gandalf the Grey, after escaping imprisonment, chose Shadowfax, much to Théoden’s displeasure, and tamed him.
Shadowfax’s extraordinary speed and understanding of human speech made him invaluable during the War of the Ring, where he served Gandalf faithfully.
SHDOWFAX, THE HORSE RIDDEN BY GANDALF IN THE LORD OF THE RINGS