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The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.

Genetics Markers Prove Dogs Have Evolved to Digest Carbohydrates and Starches

One could spend all day, or more, engaging in (sometimes heated) dialogue about what our pets should eat. Depending on your personal beliefs, education, and experience, your perspective could be vastly different from another pet owner. Even within the veterinary community, there are a wide range of recommendations as to what is the most appropriate style of feeding for our companion canines and felines.

Should your pet eat a whole-food based diet made up of nutrients identical or similar to the form created by nature, or a highly processed diet engineered into a dehydrated (and seemingly devitalized) piece of kibble?

What about the components that make up a particular diet? Should pet food have whole meats, vegetables, fruits, and grains? Or is it sufficient to feed protein and grain meals and by-products that have been coated with rendered fat and infused with artificial colors to increase palatability and appeal to owner aesthetics (respectively)?

Should you be feeding grains and starches to your pooch? Can dogs even digest them? Recently, a study published in Nature magazine proved that dogs’ domestication complements environmental and geographical changes associated with their role as companions to humans. It’s proven in their genes, which have evolved similarly to man’s and reflect dogs’ ability to digest grains and starches.

The authors of the study, titled The Genomic Signature of Dog Domestication Reveals Adaptation to a Starch-Rich Diet, conducted "whole-genome resequencing of dogs and wolves to identify 3.8 million genetic variants used to identify 36 genomic regions that probably represent targets for selection during dog domestication. Nineteen of these regions contain genes important in brain function, eight of which belong to nervous system development pathways and potentially underlie behavioral changes central to dog domestication.

“Ten genes with key roles in starch digestion and fat metabolism also show signals of selection. We identify candidate mutations in key genes and provide functional support for an increased starch digestion in dogs relative to wolves. Our results indicate that novel adaptations allowing the early ancestors of modern dogs to thrive on a diet rich in starch, relative to the carnivorous diet of wolves, constituted a crucial step in the early domestication of dogs."

As domesticated dogs are believed to have evolved from wolves nearly 11,000 years ago, their evolutionary process parallels a similar genetic shift seen in humans. Today’s dogs and humans eat and can digest a wider variety of foods in comparison to the primarily meat protein meals that were hunted, killed, or scavenged by their lupine and Cro-Magnon predecessors.

To fit modern times, we should be providing our canine companions some variety in their diets. I am an advocate of both dogs and cats eating whole food meals instead of processed diets. As ChooseMyPlate.gov does not advocate that we humans regularly eat highly processed foods, the same basic principles should apply to our canine and feline companions.

Even though today’s dogs can digest grains and starches, I don’t recommend that such nutrients form the majority of a dog’s diet. Any grains or starches made to be consumed by our pets should be whole-food based, cooked, and included in a small to moderate quantity (30% or less of the volume of a particular meal), complementing the larger percentage of meat, vegetable, and fruit ingredients.

Although commercially available and home prepared diets that are 100 percent free of grains and starches are popular, there are nutritional benefits stemming from their inclusion. Whole grains like brown rice, barley, etc., are good sources of minerals (Selenium, Manganese, etc.) and can even serve as substrates (pre-biotics) on which beneficial bacteria (pro-biotics) grow. Starches like russet and sweet potatoes, banana, etc., are rich in vitamins (A, B6, E, etc.) and minerals (Potassium, Manganese, etc.).

Part of where my concern about pets eating commercially available pet foods containing grains and starches lies in the quality of the ingredients. The majority of canine and feline diets are made with ingredients that are "feed-grade," which are of lower quality than "human-grade" and have higher potential to contain unhealthy substances (e.g., deoxynivalenol [vomitoxin], aflatoxin, etc.) according to the FDA Regulatory Guidance for Toxins and Contaminants.

Short or long term consumption of these toxins can cause inflammatory bowel disease, kidney and liver damage, or even cancer (see petMD article: Are You Poisoning Your Companion Animal by Feeding 'Feed-Grade' Foods?).

How you feed your pet is your personal choice. Nobody can force you to feed a particular commercially available or home prepared option. My best suggestion is to model your pet’s diet after that which humans are recommended to eat, which means choosing a variety of whole foods and minimizing processed foods.

What’s your perspective on how our companion canines (and felines) should eat?

Dr. Patrick Mahaney

Image: Chopstick Joe - Joe eating rice by Nicole Hanusek / via Flickr

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