I have a 3 year old English Mastiff. Ill be honest and say I do not feed him expensive food, but I think I do need to feed him better food maybe. he has been on pedigree large breed for about a yearish, and will go through times where his stool is ok one day but a few days later its very runny. This is happening a lot more recently. been to the vet had stool sample tested. nothing found wrong, gave him some stuff to help stiffen up his stool. everything was fine for a while now its back to very runny watery. thinking maybe I should try a better food.