Sticks and Stones

When a horse has a small penis, the other horses tease him by saying he's hung like a human.

Green and Laughs

Q: What's green and laughs at you while riding away?
A: A Leprechaun on a race horse!

Cowboy's Three Requests

A cowboy was riding through an old abandoned canyon trail when he was captured by a group of ruthless banditos intent on killing him. In their drunkenness, they decided to go easy on him and grant him three requests. For his first, he asked for his horse. He whispered something to his horse, who then rode off and returned with a beautiful woman. The cowboy spent the night with the woman. The same thing happened the second day. But when the horse returned on the third day with another woman, the cowboy lost his temper and yelled, "You stupid horse! I said 'posse!"