Two cows in Britain

There are two cows out in a field in Britain.

One cow turns to the other and asks, "Are you worried about this Mad Cow disease?"

The other cow responds, "Nope."

The first cow exclaims, "How can you say that? Cows all over England are getting it. I'm scared stiff!"

The other cow just looks at him and says, "Mad Cow disease, why should I be worried? I'm a helicopter."