Where is that cow from?

Heard on A Prairie Home Companion podcast:

Oli was visiting Sven who had recently bought a new cow.

Sven: This cow is funny. She farts whenever I milk her. Oli: Let me see…

They walked over to the cow, Oli sat down on the stool, pulled at her udder and the cow let out a fart.

Oli: Hmmm. Is this cow from North Dakota? Sven: Yes. How did you guess? Oli: My wife is from there and she does the same thing.

I had taken a sip of my coffee just before Garrison delivered the punch-line. It was so unexpected, most of that coffee ended up on my monitor. Had to do a major cleanup. Thanks, Mr. Keillor!