I think this topic of gse is very confusing. In the Parrots for Dummies book, a book I have seen referred to as many parrot owners bible they talk ALOT about the use of gse. It is stated that it is even more effective than surgical soap in killing germs. I am not sure about the rules of quoting from other publications so I am just going to mention that this is the cleaner of choice in this book. There seems to be lots of contradicting evidence on this topic.
I am not a fan of that book. I bought it and gave it away almost immediately. "Birds for Dummies" is co-authored by a vet and is a lot more grounded IMO. The author of "Parrots for Dummies" is a very experienced owner and trainer of parrots, but is not a biologist or vet. IMO she states as fact many things which are opinion and for which there is little evidence. It was hard in the book to sort out those things which were strictly opinion from those where there was evidence, as references were rarely cited. That kind of writing in a nonfiction work makes me insane. But I know people like it... I'm just not one of them. If it is the only book in your library, you might want to get something like Gallerstein's "Complete Pet Bird Owner's Handbook".
In the case of GSE, the evidence is contradictory and that's the point. I stated it earlier, but maybe it bears repeating... We don't know if it has any effectiveness at all. The early studies with it were very promising. However, those tests were carried out using GSE that contained preservatives. Subsequent tests using GSE that did not contain preservatives did not show a significant effect. Why is unknown, but speculation that the preservatives were actually the effective ingredient seems somewhat logical, although that has not been tested.
I use GSE with preservatives in making sprouts, but I'd never rely on it in any kind of critical situation. OTOH, it's not clear to me that trying to make our birds environments hospital-sanitary is the right answer anyway.
I guess I'd also like to point out that there is no such thing as a completely safe substance that is also a very effective disinfectant. It's sort of inherently contradictory. Germs are, after all, biological matter and anything that kills them destroys or disrupts biological matter. Granted that a mild acid like acetic acid in vinegar is not likely to kill cells in the digestive tract, which is also acidic -- but nor is it going to kill bacteria adapted to an acidic environment.
Use of these things in non-critical situations is something I'd consider myself in the vein of "probably won't hurt, has some possibility to help" and I did experiment with cider vinegar in the drinking water, but don't really like salad-scented birds. If I had an outbreak of some disease, however, you'd better believe I'd have the commercial grade kennel disinfectant out!
Hope that helps.
