Corn is a cereal plant that yields large grains. Whole corn, like you eat on the cob, is considered a vegetable. The corn kernel itself (where popcorn comes from) is considered a grain. Corn lacks in nutritional value for dogs, so it's best to stay away from any dog food that contains corn.
how to feed
Corn has a high glycemic index, it is often genetically modified, which takes away all nutrients and minerals, and although corn is gluten-free, it can still aggravate sensitive digestive systems and you will notice the corn come out the same way it went in! Corn also lacks in nutritional value for dogs and cats.
There are debates out there saying that corn seed is actually a vegetable, fruit and grain. Although it's delicious for humans, it has no nutritional value for our furry friends, therefore you should skip it!