A Mountable creature can be equipped with Barding, which shares the same armor class values as Armor from the Armor tables.

The cost of barding is equal to the base armor cost + 100 gold for every size larger than Medium.

Mounts do not have to be proficient in Barding to use it, but they do have to be willing when they are being equipped in it.

Equipping and Unequipping barding unto a Mount takes 20 minutes.

See: Mounted Combat