LAS VEGAS (AP) — Declaring Las Vegas a “cowboy town,” dozens of riders on horseback have traditionally kicked off the Wrangler National Finals Rodeo by galloping into the arena and then lining up their horses side by side as the riders tip their hats to cheers. But an equine virus outbreak this year has loomed over one of the world's most prestigious rodeos and the threat was apparent from the start: Riders walked out during the grand entry on foot. Their horses were safely kept away with strict health precautions in place.