Cecil nailed it (of course – how could it be otherwise?) with dog and cat food. Humans, in addition to believing that food (and wine) tastes better the more they pay for it, and that “natural” has any meaning when applied to foodstuffs (turds are natural), and that “farm-grown” vegetables are better than … what? manufactured vegetables? … blindly accept the claim that wheat, corn, soy, and other vegetables are either not liked by pets or in any way deleterious to their well-being.
The worst offender in selling this nonsense is Blue: their commercials talk about how our dogs and cats are descended from wolves and tigers, and that since these critters ate a lot of meat, that’s what’s best for the dogs and cats who descended from them.
Sorry, Blue, they ate what they could get to (hopefully) get the nutrients they needed, and – lacking multiple stomachs or the ability to follow recipes – they couldn’t obtain enough nutrition to support a lifestyle more active than browsing in meadows. [I know, the evolution of carnivores was more complex than this, but the bottom line is that they evolved in ways that led to high-protein diets being best for them … in the wild]
Humans, of course, know better than to accept the fallacy that what our ancestors ate is the best thing for us to eat – no, wait, isn’t that what the Paleo diet is all about? Oh, well, then maybe it’s not so surprising that we’ll buy the same argument when applied to our pets.
Pet foods that contain no corn, wheat, or soy are in fact better – for Blue and other pet food companies: they’re raking in the green. Millions – no, probably over the years, “billions and billions” of dogs and cats – have not just survived but thrived on foods that contain corn, wheat, and soy.
And, as Cecil notes, there’s no intrinsic benefit (other than yuck factor) to muscle meat over “by-products” in terms of nutritional value. And yuck factor isn’t a consideration to a critter that will eat rotting corpses and turds, even if they knew (and cared) that they were eating snouts, ears, and innards. In fact, they may well think “Yum!”
The dogs who have been members of our pack have all gone absolutely ape over cheese, peanut butter, and popcorn, none of which was presumably available to their ancestors; and other than the popcorn they’ve had pretty good nutritional instincts. But for their primary nutrition, they’ve all eaten a high-quality dry food with a good nutritional profile – check out the FDA website and the AAFCO website (which the FDA page endorses) for guidance.
I’d say I was surprised that people are so easily gulled by pseudo-science and outright lies, but in a country where almost half of the population rejects evolution, and a failed real-estate magnate can make it into a presidential election, all bets are off.