Boy does this topic hit close to home.
Carbohydrates are absolutely NOT necessary for ANY dog. Ever.
I went through about a 7 month battle with my Corgi. Constant diarrhea, extreme weight loss no matter how much or what I fed him. A couple thousand dollars in tests later, we discovered that he had a type of SIBO that is triggered by carbohydrates in the diet, which are unable to be used by his body, and just kind of "hang out" rather than pass.
While not every dog will have this problem, and most dog will do seemingly fine with carbs in the diet, the whole experience atught me a few things about my dog.
1. Carbohydrates are almost on the same level as toxins for a carnivore.
2. Feeding a diet that is not natural to his species is asking for serious trouble.
3. Carbohydrates are the root of MANY problems, not just this rare one, so why risk it at all? Cancer, diabetes, SIBO... no, thanks.
4. While I feel that SOME dog food companies really do care about the welare of dogs, NONE care about them as much as they do their bottom line. Carbs are cheap. Meat is expensive.
Unfortunately there is no such thing as a dog food with the appropriate carb content. (zero) While I had interest in raw for some time, I kept putting it off and putting it off because I thought kibble was "working" so why change it? Then the vet looked at me and told me if we don't intervene, I would lose my Corgi... my absolute best friend in the world. While the vet opted to put him on an extreme steroid treatment as well as an extreme high dose of atibiotics that would affect his quality of life for the worse. I opted to simply remove the carbs, and after TWO days he was already improved incredibly. I raw feed two of the three dogs living with my. My Corgi and my Boxer both eat nothing but raw meat, bones, and organs from the grocery store intended for human consumption. Even though my Boxer never had health issues to begin with, I see such an incredible difference in both of them verses kibble fed dogs.