AFAIK there never were any at USIOA; were you thinking of Busch Gardens in Tampa?
If so, the answer is that the matched white-stockinged bay Clydesdales owned by Anheuser-Busch left BG when the park was sold, but the new owner replaced them with a smaller herd of black Clydesdales. There are not enough for an 8-hitch, but they are still pretty.