
Hi Lisa,
He could be allergic to the rice? Rice along with several other grains is contained in most dog foods and although regarded as the least likely to cause a reaction can and does cause problems for some dogs. It can also be the case that while your dog has been able to eat boiled rice as prepared at home, he may not cope so well with the processed version in dry kibble.
There are so many ingredients in commercial diets that finding what is causing a reaction can be difficult and it may be worth asking the vet to arrange for tests to be done to isolate the allergen(s). If not insured it can be an expensive procedure and therefore it may be worth looking at a minimum content diet such as Wafcol's Salmon & Potato. For this trial to be effective, everything including treats, titbits, chews, rawhides, sips of your morning cuppa :P etc must be
completely excluded.
Having said that it may not necessarily be a food intolerance which is causing the diarrhoea - has your vet done a faecal sample and full blood panel to rule out other causes?
Good luck, hope your vet is able to shine more light on possible cause. Let us know please. Teri :)