Some Kentucky estates come with an impressive equestrian pedigree. Castleton comes with more than two centuries of it. The sprawling Lexington property dates to 1793 and has played a role in Thoroughbred, Standardbred and American Saddlebred history, with horses ranging from Kentucky Derby winner Ben Brush to three-time Eclipse Award winner Gio Ponti connected to its pastures. Now, all 951 acres are...