What You Need to Know About Fillers in Dog Food

Field of wheat, one of the grains that can be useful for homemade dog foodField of wheat, one of the grains that can be useful for homemade dog food

“I only feed my dog a grain-free dog food because it doesn’t have fillers which are bad for pets.”

I hear this a lot during my nutritional consultations with pet parents. The word “filler” is used to describe a “bad” ingredient and generally refers to grain products in pet food.

Grains are carbohydrates. But so are the potatoes, sweet potatoes, beans, and tapioca typically used in grain-free diets. So, why is one type of carbohydrate given the bad name “filler” and another type of carbohydrate considered better nutrition?

What is a filler?

By definition, any filler is an ingredient that adds bulk to a diet without adding any nutritional value. The only ingredients in pet food that fit that requirement are fibers. Beet pulp, tomato pumice, the fiber in beans, potatoes, sweet potatoes, and vegetables are true fillers. People and pets do not get direct nutritional benefits from fiber but it adds to the bulk of the diet.

But even though it is a filler, fiber feeds the “good” bacteria in the colon. In proper amounts, fiber is a healthy filler. In excessive amounts, it can interfere with proper digestion and absorption of important amino acids, fats, minerals, and vitamins. So how are carbohydrates different from fiber?

Carbohydrates Contain Energy

All dogs require lots of energy, even when they are at rest. Lost energy or calories need to be replaced by the calories in food. Only 3things in food have calories: proteins, fats, and carbohydrates. That’s it. Protein and carbohydrates contain the same number of calories per unit of weight and fat has more than twice the number of calories per unit of weight.

Dog food, commercial or homemade, is made based on the calorie needs of dogs and cats.

Protein and fats are added in amounts to ensure that all of the protein, amino acid, and essential fatty acid daily requirements are met. But protein is more expensive than carbohydrates. Carbohydrates like grains, beans, potatoes, or tapioca can be used to supply the rest of the needed daily calories. In fact, pet food cannot be “popped” into kibble unless it contains at least 50% carbohydrates.

All carbohydrates, including grains, also contribute small amounts of protein, vitamins, and minerals to the diet. These qualities hardly make grains a filler, but rather an inexpensive source of calories and other nutrients. That is why it is possible to feed a dog dry, kibbled dog food for less than $1 per day.

Using grains in homemade dog food also makes those recipes more affordable.

By adding calories in the form of barley, cornmeal, oats, rice, macaroni to homemade diets, more pet parents can afford to feed their dogs a food that is superior to regular, commercial dog food. Dogs that don’t tolerate the “grain meals or glutens” in commercial dog food generally have no problems when it is in the form of grains or grain products (macaroni) in homemade dog food.

In truth, carbohydrates and fiber are not fillers. Used in proper amounts, they can contribute to a healthy homemade diet.

Dr Ken Tudor, veterinarian who created Hearthstone Homemade


Dr. Ken Tudor is a recognized expert and leader in the field of pet nutrition and fitness. In addition to co-founding a national campaign to help fight dog obesity, he developed a pet weight management program and served on the American Animal Hospital Association task force to develop their Weight Management Guidelines for Dogs and Cats.