Well, actually, there are excellent guidelines on dog and cat nutrition (there are even FDA rules for them) because we know A LOT about them and they are, after all, not only domesticated species but also we've been feeding them for, literally, tens of thousands of years so, with them, it's just a matter of accessing the data out there and making a decision: crap food made out of soy, grains and meat by-products (but cheap), or good food made out of real meat (and expensive). It's parrots nutrition that we don't really know about... Nobody knows enough, not the breeders, not the food manufacturers, not the avian vets, not the biologists, not anybody! And, yes, there are all these opinions about what is right and what is wrong but I do see a very strong trend towards feeding more and more fresh food instead of processed. Me, I am a control freak and a perfectionist so I not only have to know for a fact that I am giving them the best but also that I know EXACTLY what they are getting. So far (25 years and counting), it has worked very well because I've never lost a single bird to anything related to nutrition (and I include eggbinding here!), quite the contrary, birds that have come with conditions caused by malnutrition have gotten better so, the way I look at it, my way is most definitely 'not broke'