Where do cows go, when they go out at night? To the Moo-vies of course!
Why did the cow jump over the moon? Because the farmer had cold hands.
Why don't cows have money? Because the farmers milk them dry.
Why do cows wear bells? Because their horns don't work.
Why don't cows listen to you? Because it goes in one ear and out the udder.
What do you call a cow that plays a banjo? A moo-sican
What sound does an exploding cow make? "COW-BOOM!"
Why does a milking stool have only three legs? Because the cow's got the udder.
Why did the cow go to drama school? To become a moo-vie star.
What do you call a cow eating grass? A lawn moo-er.
What do you call a cow that can't give milk? An udder failure.
GilraenH
Pro 
Those are some groaners and no mistake.