You are describing exocrine pancreatic insufficiency (EPI). This is a rare problem in ferrets. What other signs is he showing besides the weight loss (ravenous appetite, large amount of feces/mucoid diarrhea, anemia from malnutrition)? If it is EPI then the 2 big things to treat it would be : 1) a bland diet such as Gerber's baby food (chicken or turkey), or Hill's a/d and 2) a powdered pancreatic enzyme product to add to his food. Some will also need an antibiotic for bacterial overgrowth and a vitamin-mineral supplement. Treatment will likely be needed for the rest of his life. Hope that helps, Jerry Murray, DVM [Posted in FML issue 3470]