"Strike Up Conversation" joke

These 2 cows are standing in a paddock. They strike up a conversation, as cows are want to do.
"Hi, how are you?"
"Good, how are you"
"Oh, pretty good.. . actually that's not quite true. I'm a little worried really"
"Good heavens, why. What could you have to worry about?"
"Well, it's Mad Cow Disease, actually"
"But we're in Australia; it's not going to effect us"
"You never know. Viruses are very good at traveling. You can never be sure where they're going to turn up next. To be honest, I can't believe you're not concerned yourself"
"About Mad Cow disease?"
"Yeah"
"Well it's not really my problem is it"
"Why not!"
"Well I'm a rabbit"