This morning when I went out to feed my geese, I noticed one that cannot stand up. It was running around with all the others last night. I picked her up and looked at her legs and can't find anything noticeable. She tried to flap her wings and get away so it appears to be a leg issue. I'm new to geese and I've read a lot about niacin and brewers yeast when I did a search, so I'm wondering if that might help. I currently feed them Purina Flock Raiser. I hope someone can give me some advice. Thanks!