In the old west an old farmer took a young wife

As they got into the wagon to go home one of the horses bucked. The old farmer hit it with his whip and said, "That's one."
On the trail the horse bucked again and the old farmer smacked it with the whip again and said,
"That's two."
As they pulled up in front of the farm the horse bucked again and the old farmer said,
"That's three", pulled out his shotgun and shot it dead.
"Oh my God," the young wife screamed, "What did you do that for/"
The old farmer looked at her and said  
"That's one."