Probably because they'd find it hard to get up stairs.

They're scared. Reminds me of the book Wayside School is Falling Down. :)

Cows can go up but not down. It's cos o evolution. They're used to living in open fields with no slopes, especially slopes in the form of stairs. Their bone structure won't allow it

there is too much weight in their rear wheels. their back legs arent designed for stairs. they could probably propel themselves up stairs with their back legs.

Because they are not allowed upstairs. They make the place smell.

They can they just wont.

They can ! They're just too lazy !! They'd rather lay around upstairs , eat Bon Bons and watch soap operas all day !!! I hear they are especially big fans of the Chick-fil-A commercials .

1) "It is possible to lead a cow upstairs but not downstairs, because a cows' knees can't bend properly to walk back down." Source: http://www.bluemoo.net/45cowfacts.html http://www.nal.usda.gov/outreach/facts.htm 2) "OK, imagine you are a cow. Now walking up, most of the weight of your body is down and back, and your knees bend helping you push yourself up. Now walking down, most of the weight is on your front legs, and your knees bend and point down the stairs, and with all the weight and the very real possibility that you could tumble down frontwards, you just won't do it. But, you say, I see cows go down hills all the time in John Wayne movies. Yes, they do down hills, but the sides of the hills are not broken up by STEPS that cause you to , as it were, go on faith that the next step is short enough that you won't trip. Think of it as you would a child, kids will first start to climb UP steps, but getting them to go down takes a lot of patience and care by the parents, till they learn to walk down." Source and further information: http://wiki.answers.com/Q/Why_won't_a_cow_walk_downstairs 3) Here a forum about this question (with some suggestions): "Why can't cows walk downstairs?" "they can in fact walk down stairs but the steps have to be wider (about 20 inches). Thinking about it I doubt if a cow can raise it's leg much at the 'hip' or 'shoulder' equivalent " Source and further information: http://www.qi.com/talk/viewtopic.php?t=8874&view=previous&sid=de2aae089586caf2f41dab16146b3f80 4) "You know how it is - you've led a cow up some stairs, forgetting the basic fact that cows can't walk down stairs! We've all done it - but what to do about it? There's a simple solution - call BOVINE DESCENDERS. With over fifteen years experience of getting cows downstairs, we can help you with practically any cow-stuck-upstairs scenario. We've worked with most of the big names in the cow/stairs industry, several famous rock bands, and hold exclusive cow-descending contracts with over half of England's local authorities." Source and further information: http://www.hyperactive-stage.co.uk/bovinedescenders/ 5) Further information: - "Can cows walk down stairs?" http://www.answerbag.com/q_view/60509 - Humor with cows: http://www.dmoz.org/Recreation/Humor/Animals/Cows/

They have a hard time moooooooving that way.

I've spent a good portion of my life on a Ranch with cows. I think if a cow had a good reason too, it could climb down stairs. It may not do it very quickly or gracefully but it could do it. If not, it would probably just jump. Believe it or not, cattle can jump very well.