Vet seems to think dog has above and wants him on a low fat diet. Has recommended one of the science diets dry foods which you can only get on prescription, or on line from certain places. Obviously this is very expensive. I have at the moment put him on chicken, fish and potato. Obviously he is not getting the full mineral and vitamins he needs. What else can I give him for fibre ? Also vet does not want him on vegetables either because they might ferment in his tum? Any input gratefully received