My adult female pekin duck named Berkeley has diarrhea for several weeks. losing weight. she has as 12 or more poops a day. some are mostly normal but many are very runny. various colors reflecting what she is eating. she is eating well(crumble and greens) plus some celery in morning and some tomato in evening. I put some rolled oats and sometimes cracked corn in the crumble. I also add some grit for her. I give her some oyster shells on the side since she is a layer, diet had not changed when this began. I think the only difference was new bag of nutrena layer feed which she had before. the vet says the tests show bacterial infection. kidneys are fine, no foreign objects found and she is laying normally. vets have tried several antibiotics-septra SMZ/TMP in suspension, nystatin, and Ceftazidine by injection. The Ceftazidine helps a bit but not much. the vet won't even discuss probiotics-she barely asked what i fed her. will probiotics help? could the bag of Neutrena have tainted feed? I bought it at a feed store. Please help.