You're entirely correct. Clearly I spoke without thinking. I am sure that corporations are using every part of the animals. If they do not feed them to one another, they take everything they are not legally allowed to sell to humans and mash it up to make poison that they then market as "quality dog food."
It actually really bothers me that I am forced to be a part of the meat industry, because I have a large puppy, and I cannot be sure that that vegetables will provide him with everything he needs to grow. But, I would never buy him that cheap shit that they claim to be "food."
We, as a people, eat an awful lot they tell us is food that is not. As long as it tastes good people will eat it