I don't think it would be a problem, no. They're just saying as nutrition, it is bad. Generally, dog food is not nearly high enough in protein, and ferrets need a high protein food. In fact, the occasional dog food kibble is probably better than like the commercially available "yogies" which are really high in sugar. I'd only be careful they don't choke on the chunks of the bigger kibble.
Actually, I feed my dogs Innova Evo small bites dog food (mixed with Chicken soup for kittens), and they do well on it...but the Innova is like 42% protein? (I think).
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