The simplest answer is that when your dog gets loose it does not run to the nearest grain field and eat the grain. The just don’t naturally eat wheat, corn, rice, barley, oats, canola, sorghum, and/or soybeans.
The more complex answer is that your dog’s digestive tract has formed to digest meats and fats. A dog releases hydrochloric acid when eating and this is why they can eat road kill or something dead in your yard without getting sick. Your dog is not a ruminant like a cow, sheep, goat, deer, elk, etc. These animals have four chamber stomachs, chew the cud, have a digestive tract 20 time the length of their bodies, and enzymes that aid in grain digestion. Your dog has a single stomach, does not chew the cud, has a digestive tract 2 1/2 times the length of their bodies, and has enzymes that aid in meat and fat digestion. Knowing these things about your dog is so important because 70-80% of your dog’s immune system is in their digestive tract. Feeding your dog grain will stress their immune system which opens the door for a multitude of diseases to come in. On top of weakening their immune system, your dog will also not be able to extract the proper nutrients from the grains, because they are not designed to. Without proper nutrients your dog is left under nourished and with a weak immune system.
We feed grain free food to our dogs so that they have strong immune systems, receive proper nutrients, and are as healthy as possible.