I had a mare that as soon as she would come into a clean or freshly bedded stall she would urinate. I think it is probably a marking thing. It didn't matter if it was her stall or a different stall, she always did. Now if she came into her stall and I had not added fresh shavings or rebedded it completely she would not urinate. But if it had new or added that was the first thing she did, You would barely get the halter off and she would be marking.