Sad thing is, I fed Science Diet (for dogs) many years ago. Paid a premium price for a food that I thought was premium. Never questioned the ingredients list... the packaging label told me all I needed to know! Maybe that is why our Danes were stolen... someone wanted to feed them better.
Don't feel bad, Lola. I fed the "prescription" carp to my cats because I didn't know what else to do, I was desperate to get them to keep their food down, and I didn't know enough about pet food at the time to question my vet. I still remember looking at the ingredients and wondering why there were so many plants/carbs in them, and then I told myself, "well, there's grains in a mouse's stomach . . ."
Not realizing how small a mouse is, and it's stomach is even smaller, and not realizing that the mouse is pre-digesting the material for the one that eats it.
We live and learn.