I am not exactly sure. I treated our two pups Yuna and Tidus for Coccidia as a preventative- and they never, ever had the runs or diarrhea ever since. This was when they were just little pups. Now Jesse would have bouts of 'slimey' poos before we put her on Fromm, and many times she could not hold it til morning. I think hers had to do with her intestines and digestive system and finding her the right food. Never had a slimey poo since.