Amusing Joke

An old, blind cowboy wanders into an all-girl biker bar by mistake.
He finds his way to a bar stool and orders some coffee.
After sitting there for a while, he yells to the waiter, 'Hey, you wanna hear a blonde joke?'

The bar immediately falls absolutely silent. In a very deep, husky voice, the woman next to him says,
'Before you tell that joke, Cowboy, I think it is only fair, given that you are blind, that you should know five things:
1. The bartender is a blonde girl with a baseball bat.
2... The bouncer is a blonde girl.
3. I'm a 6-foot tall, 175-pound blonde woman with a black belt in karate.
4. The woman sitting next to me is blonde and a professional weightlifter.
5. The lady to your right is blonde and a professional wrestler.
'Now, think about it seriously, Mister. Do you still wanna tell that joke?'
The blind cowboy thinks for a second, shakes his head, and mutters,
'No...not if I'm gonna have to explain it five times.'

I don't get it.If he's old and blind how can he round up cattle?

he may have been a deputy, and not have anything to do with cattle