dodgy tummy - what are the possible triggers?

[paddythepooch]

Pooch has had dodgy tum lots. Moved him to Nature diet and that really helped. Have worked out that he gets a runny bum with anything with wheat in it - so really careful to avoid that now. However, he still gets the runs from time to time and I am trying to work out what it might be: his treats are either pure turkey or pure liver and he has a carrot a day.

Am trying him on one of the flavours of the nature diet at a time to try and eliminate a particular flavour. He has the fish, rabbit and turkey or the chicken one.

Trying to work out what the possible trigger is. Any ideas?