As a quick refresher from our earlier blog post, the microbiome is the ecosystem of bacteria and other microorganisms living on or inside an animal, and in this case, our dogs. There can be many microbiomes in a single animal, including the gut, skin, and mouth. Both humans and dogs have microbiome communities like this! The microbiome is extremely complex, and the source of both emerging and ongoing research. Every dog has a gut microbiome that is unique to them. Your dog’s age, breed, weight, exercise levels, genetics, antibiotics taken, and more, can affect what their microbiome is made up of. As you may suspect, diet also has a significant impact on the constituents of your dog’s microbiome. In this article we will examine diet in more detail, and some of the latest insights from the science community.
Which bacteria make up our dog’s microbiome?
Most of our dogs’ gut microbiome can be found in the intestines.1 The small intestine is home to a broad diversity of bacteria, while the large intestine only is home to anaerobic bacteria1 – or those that can only grow and survive without any oxygen present.
When scientists discuss bacteria, we often classify them into taxonomic groupings, based on the bacteria’s structure or function. Genus and Phylum are two examples of taxonomic groupings. Phylum is broader than genus. When it comes to gut health, there are three main bacteria phyla: Fusobacterium, Bacteroidetes, and Firmicutes and within each, dozens of genuses.1 Each of these phyla serve a special and unique role when it comes to breaking down the various macronutrients in your dog’s food –fats, proteins and carbohydrates - and digesting each of them into appropriate micronutrients that can be absorbed by the body.
Interestingly, when your dog consumes more of one macronutrient than another, their microbiome changes to accommodate the function needed to create viable micronutrients for the body. For example, when there is an abundance of carbohydrates in a dog’s diet, the bacteria that thrive on carbohydrates can flourish, and then constitute a relatively larger percentage of the microbiome compared to other bacteria that rely on fats or proteins. These carb-loving bacteria will happily consume these carbs, since this is their main source of energy. In other words, their metabolic activity (their way of creating energy) relies on that specific macronutrient in some way.2 All macronutrients are necessary to create a balanced, complete diet. Carbohydrates are essential during times of high energy needs such as growing as puppies, gestation periods, and during lactation.3
Taking the diet-specific comparison one step further, let’s talk two specific canine dry-food diets: a low-carbohydrate and high-carbohydrate diet [for reference, according to published literature, the minimum nutritional protein requirement for dogs is 18% and a maximum of 29%.]3. Li et al.4 established that indeed, in a low-carb diet, there was in an increase in specific bacterial genuses (Clostridiaceae, Lachnospiraceae, and Ruminococcaceae) and a decrease in others (Erysipelotrichaceae, Veillonellaceae, and Lactobacillaceae). Interestingly, this study also showed that there was a higher ratio of Bacteroides: Prevotella. Inversely, with a high-carb diet, there as an increase in Bacteroides and Firmicutes phyla as well as a 4.6x increase in Prevotella than in the low-carb diet. There was also a higher ratio of Bacteroides: Firmicutes phyla in the HCLP diet.
What is Prevotella?
Prevotella is a member of the Bacteroidetes phylum, with many species. It is an anerobic, single-cell, non-motile bacteria that lives in our dog’s gut. As discussed above, Prevotella has shown to have a strong association to the levels of carbohydrates in a diet, especially those derived from plants.4 This is because the purpose of Prevotella is to help breakdown complex carbohydrates, present in fruits and veggies. This species can breakdown tough fibers like xylan in plants (like the grass our dogs are bound to eat) but also simple sugars like glucose. Prevotella is also associated with different types of chronic digestive ailments. For example, it is sometimes observed that a decrease in Prevotella can accompany a gastrointestinal disease. This decrease of bacterial species reduces the energy source (short chain fatty acids) for the cells in the colon.
Scientists at DIG Labs are learning how to use Prevotella as a biomarker for carbohydrate load in a dog’s diet. This is important because, despite dog parents’ best attempts to balance a diet, carbs can sneak in, through treats, table scraps and more, and create a macronutrient imbalance, especially when there is a weight management or chronic condition being managed.
Why are the dietary microbiome differences important?
As discussed, in the high-carb diet, overrepresentation of carbohydrate digestion and absorption and absorption of minerals was shown. This finding indicates that the changes in abundance of the happy bacteria in the gut microbiome are capable of transforming the carbohydrates that they’re ingesting, which increases the availability of minerals, and promotes absorption in the large intestine.4 Bacteria that feast on carbohydrates (or ferment them) may produce a compound called butyrate when breaking down fiber into glucose, a simple sugar molecule that can be readily absorbed by the body. In addition to prevotella, firmicutes are also known to have high carbohydrate fermenting power.
Other bacteria can be proteolytic. Proteolytic bacteria refer to those that produce proteolytic enzymes which are enzymes that break the bonds in protein molecules into amino acids that can be used for energy. Examples of proteolytic bacteria include bacteroides and proteobacteria2.
While the dog gut microbiome is still being extensively researched, we do know the basics. Our dogs’ genetics, age, breed, weight, activity levels, and diet affect their gut microbiome composition. Most commercial kibble brands are relatively high-carbohydrate (and therefore low protein), due to the limitations of dry food manufacturing, so we tend to see higher levels of Prevotella, Clostridium, Lachnospiraceae, and Ruminococcaceae species in the gut microbiome. While these bacteria are great at fermenting all those carbs that our dogs are consuming to meet their energy needs, it may also be an indicator of a macronutrient imbalance. Importantly, Prevotella is a versatile bacterium that can break down molecules both complex and simple. Knowing how your dog’s diet affects their microbiome and their body overall will allow you to make more tailored decisions on what you feed them.
References
- Pilla S. The Role of the Canine Gut Microbiome and Metabolome in Health and Gastrointestinal Disease. Frontiers in veterinary science. 2019;6:498-498. doi:10.3389/fvets.2019.00498
- Bartges, J. Gut Microbiome and Obesity. Hill’s Global Symposium, 2019.
- Sanderson, S. Nutritional Requirements and Related Diseases of Small Animals. MERCK MANUAL Veterinary Manual. Merck Sharp & Dohme Corp. 2013.
- Li L. Effects of the dietary protein and carbohydrate ratio on gut microbiomes in dogs of different body conditions. mBio. 2017;8(1):e01703-16-. doi:10.1128/mBio.01703-16