
Hi Fiona,
I've used JWB previously and found it didn't agree with my youngster (frequent large & soft bowel motions). I switched all my dogs onto Wafcol Salmon & Potato - which is also a hypoallergenic food that is also soya free (an irritant to many dogs with recurrent tummy problems). They do a Salmon & Corn version but I personally would not feed a maize/corn based diet to a dog presenting wheat intolerances- especially not a Shepherd.
GSDs are renowned for suffering a variety of GI problems :( Has your vet done blood and faecal samples on your dog? I realise these can be quite expensive and switching to a novel protein diet is certainly a good course of action as first base, (please also remember to eliminate ALLother foods from his diet including treats, chews, table scraps). However if you find that he is not improving on this diet change I would strongly recommend having the tests done - there are numerous complaints presenting as runny stools or vomitting which genuinely require meds along with diet monitoring but food intolerances can rapidly develop to multiple sources so messing around with diet too long inhibits potential choices in the future.
Good luck with him, HTH, regards Teri :)