URBANA, Ill. – For decades, kibble has been our go-to diet for dogs. But the dog food marketplace has exploded in recent years, with grain-free, fresh, and now human-grade offerings crowding the shelves. All commercial dog foods must meet standards for complete and balanced nutrition, so how do consumers know what to choose?

A new University of Illinois comparison study shows diets made with human-grade ingredients are not only highly palatable, they’re extremely digestible. And that means less poop to scoop. Up to 66% less.

“Based on past research we’ve conducted I’m not surprised with the results when feeding human-grade compared to an extruded dry diet,” says Kelly Swanson, the Kraft Heinz Company Endowed Professor in Human Nutrition in the Department of Animal Sciences and the Division of Nutritional Sciences at Illinois, and co-author on the Journal of Animal Science study. “However, I did not expect to see how well the human-grade fresh food performed, even compared to a fresh commercial processed brand.”

Swanson and his team fed beagles four commercially available diets: a standard extruded diet (kibble); a fresh, refrigerated diet; and two fresh diets made using only USDA-certified human-grade ingredients. These fresh diets include minimally processed ingredients such as beef, chicken, rice, carrots, broccoli, and others in small chunks or a sort of casserole. The dogs consumed each diet for four weeks.

The researchers found that dogs fed the extruded diet had to eat more to maintain their body weight, and produced 1.5 to 2.9 times as much poop as any of the fresh diets.

“This is consistent with a 2019 National Institute of Health study in humans that found people eating a fresh whole food diet consumed on average 500 less calories per day, and reported being more satisfied, than people eating a more processed diet,” Swanson says.

The researchers also found that the fresh diets uniquely influenced the gut microbial community.

“Because a healthy gut means a healthy mutt, fecal microbial and metabolite profiles are important readouts of diet assessment,” Swanson says. “As we have shown in previous studies, the fecal microbial communities of healthy dogs fed fresh diets were different than those fed kibble. These unique microbial profiles were likely due to differences in diet processing, ingredient source, and the concentration and type of dietary fibers, proteins, and fats that are known to influence what is digested by the dog and what reaches the colon for fermentation.”

Commercially available, fresh prepared whole-food diets have been around for a decade and despite anecdotal reports of health benefits, some nutrition experts were concerned about a lack of scientific evidence to support the feeding of these diets. Swanson published an earlier study in roosters to show the same human-grade fresh diets were up to 40% more digestible than kibble, and his new study in dogs strengthens those findings.

The article, "Nutrient digestibility and fecal characteristics, microbiota, and metabolites in dogs fed human-grade foods,” is published in Journal of Animal Science [DOI: 10.1093/jas/skab028x]. Authors include Sungho Do, Thunyaporn Phungviwatnikul, Maria de Godoy, and Kelly Swanson. Funding was provided by JustFoodForDogs LLC.

The Department of Animal Sciences and the Division of Nutritional Sciences are in the College of Agricultural, Consumer and Environmental Sciences at the University of Illinois.