Possible allergy to chicken and use of Hills z/d dog food

Our customer asked:

We think our dog has an allergy to chicken (to be confirmed) we have been
advised to put him on Hills ZD but notice from the ingredients that this has
chicken in, however the vets say that this chicken has been treated in such
a way that the dogs body will not recognise it as chicken. Please help we
are desperate to find a food that agrees with him, he has constant upset
tummy. He has also had giardia parasite which we think has also not helped
but our poor dog only weighs 25kg for an adult golden retriever.

Our reply:

If you dog has a food allergy, then Hills z/d should be suitable, regardless of what the allergy is to. This is because z/d is processed in such a way that none of the proteins are present in a form which can trigger the allergy. The protein molecules are massively reduced in size adn the immune system cannot recognise them as chicken. It should be OK to use. That does not mean that it will definitely be the answer to your dogs digestive trouble, but it might well be. Lots of dogs do respond extremely well to it, so you should certainly try it I would say.

Giardia may or may not be contributing to the problem, but your dog will probably shed this parasite in time anyway. If not, there is medication which could be tried. However, I would try the diet first. (Purina HA would be an alternative product. It is based on the same idea, but no chicken is used in its manufacture. It seems to work very well indeed for many dogs.)

You could try adding Pro-kolin Enterogenic to the food for a while. This is proving to be a very popular product, and many dogs seem to get a great deal of benefit from taking it. It can be given with any food.