I think it's because these foods have a low meat content and have lots of additives in, so basically it's like giving a kid smarties. These foods can send dogs hyper.
Although some dogs do, do well on it.
My lab used to be fed pedigree wet food, until I found out what was in it, we've now changed to Nature Diet and although he's still a hyper lad, he's a lot calmer than what he was.

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