I had my lovely old dog at the vet on Friday, was really about his leg but while there I mentioned that Cracker gets an upset tummy quite a lot 
We did realise a while back that anything with gravy affected him so we cut that out but the tummy upsets are getting a bit more frequent and to be honest it's no fun getting woke up in the middle of the night and having to clean up poo!
Anyway the vet suggested changing his food from his usual Winalot to Chappie, she says it's easier to digest.
But, I forgot to ask her if I should change his food straight away or perhaps give him 1 tin of Chappie mixed with 1 tin of Winlot for a few days till he gets used to it then give him all Chappie.
Any advice? or does it really not matter, just dont want to upset his tummy if at all possible.