I have 2 dogs that cant tollerate chicken at all, it gives them terrible collitus (snotty pooh), they quite often get the runs if i give them anything other j.wellbelloved dry mix, but we still like to spoil them with treats, after many expensive trips to the vets a lady who keeps alot of dogs down our road told me about Kalin and morphine you can get it from the pharmicist, I spoke to the vetsand showed her the bottle before giving it my dogs and she said it was the same as what they prescribe for diarroha its only �2.39 a bottle and you only need about 4 drops as apposed to �10.00 for the vets stuff plus consultation fee..... Try frozen white fish from asda �2.99 10 fillets with the rice instead of chicken for a week and gradualy add the dogs main diet back into it along with k&m till he is back to normal, also phone the vets to ask for advice.
hope it helps