I changed my cat's food rather suddenly a few weeks ago (ran out of the old food and didn't realise so had to start the new kind) and he's had runny poo ever since. He's seen the vet who suggested changing it back gradually. Anyone else had experience of this? I know if you chop and change a cat's food it upsets their innards (heaven knows why given that they catch and eat mice and all kinds of other things) but I would have expected his insides to settle by now.