Well, sort of! Horses can be cowboys, too. :D There's a poem I read called "The Best Cowpokes Aren't Always Human," which is actually about an ape that's a cowboy, but I originally thought the poet was talking about horses. They're such partners in the cowboy life, and treated on a par with the human cowboys. Or should be, anyway (ie, No Rest for the Horse).

Ooh, what an interesting idea! I'd like to read that poem, if you ever get around to writing it.