i have a cow that just started stepping higher than normal with her front feet and staggering with her backend .She still gets up and down and is still eating and drinking but is really loose , like just water coming out of her.
Get someone to look at this cow - vet or a neighbour who knows a lot about cows - or otherwise shoot her. Doesn't sound like this is a case where you can spend the time debating it on an online forum.
I assume by now your cow is either dead or alive (guess there aren't many other options).
Ideas are too late, but since it's fun to speculate, and for future reference, my first thought is getting too much carbohydrate - either grain, fruit, bread, or whatever. Signs of carbohydrate overload do include diarrhea and staggering.
She is still alive and doing better .Walking fine ( i think she had infection that affected her nervous system )she lost alot of weight but is doing better now.
Might have done like the old rancher I used to work for when I was a teenager.
I have been sittin a horse a many a time with him and heard him say , I'll be surprised if that old cow makes it as we rode away.