The Gut Microbiome And Your Dogs Health

A healthy, and Functioning Gut Microbiome is an important part of maintaining proper health. The Gut Microbiome is the group of organisms within the digestive tract. They aid in digestion and helps modulate the immune system. 

Several studies have shown that Probiotics supplementation can improve digestibility, decrease flatulence, and improve stool consistency and volume. See (Administration of Bacillus subtilis) (The influence of a probiotic product with Bacillus subtilis)

Research does indicate however that in order for probiotics to be effective the minimum is One million Colony Forming units per day, but the recommended amount is closer to one billion CFU’s per day on dogs that are experiencing stress.

Many companies vary their listing of Colony Forming units. Some list them per Ounce, Some Per Gram, Some Per half teaspoon. So it is important to read the label.

Oftentimes when discussing the gut microbiome we concentrate primarily on how it affects your pet’s gastrointestinal health. Whether giving pre and probiotics helps with Bladder Stones, Flatulence, Acute and Chronic Diarrhea, preventing infections, repairing the gut microbiome after antibiotics. Much attention has been given to the research on the effects of metronidazole, and how it impacts your pets microbiome.

When the Gut Microbiome is not functioning properly this is called Dysbiosis. Dysbiosis has been shown in humans and rats to contribute to kidney disease, inflammatory bowel disease, obesity and even heart failure. The Gut microbiome brain axis is gaining more widespread acceptance, and is being further investigated everyday. For example there is research suggesting that the gut microbiome also plays a role in anxiety and depression.

I remember listening to a podcast probably between 8 or 9 years ago about fecal matter transplants, and how it was being used to treat people with Multiple Sclerosis. Since that time the use of fecal matter transplants has been gaining more widespread acceptance and is being looked at as a possible treatment for a myriad of neurological conditions.

Whether the effects of dysbiosis also applies to dogs is not yet fully known, but it is starting to be investigated. More research needs to be conducted on the wide ranging effects of the gut microbiome on our pets health. We need research to determine what truly constitutes a healthy gut microbiome for our dogs and cats. There needs to be more research comparing Raw Fed Dogs with Kibble Fed Dogs. There needs to be research comparing the different raw feeding models. ie Commercial Complete and Balanced Raw, BARF, Primal. There needs to be research looking at those feeding a gently cooked diet.

In this post we are going to look at two early studies that I believe demonstrate the need for more research on the potential role of gut microbiome on our pets health.

Heart Disease

Heart disease in dogs is a growing concern of many owners especially those of large and giant breed dogs.

The First study we are going to look at involved 50 dogs. 15 Healthy Dogs and 35 dogs with Congestive Heart Failure. The group with Heart Failure was compromised of 16 dogs with LCHF, 15 RCHF and 4 with BiCHF.

The causes were myxomatous mitral valve degeneration, dilated cardiomyopathy, congenital heart disease affecting the tricuspid and pulmonic valves, and pulmonary hypertension.

All of the healthy dogs and most of the CHF dogs were eating commercial dog food, but more owners of CHF were also giving their dogs human foods. Given that many dogs will lose their appetite with the development of CHF, it is often recommend to feed different types of foods to avoid cardiac cachexia (Body Wasting).

It should be noted that the CHF group had a lower body condition score, muscle condition score and appetite than the control group.

Now to the results.

There was little to no difference in the Alpha Diversity. In one of the analysis in Beta Diversity there did appear to be a trend toward greater diversity.

Phylum Control CHF
Firmicutes 46.8 47.3
Fusobacteria 25.8 20.6
Bacteroidetes 17.7 17.7
Proteobacteria 2.6 6.6
Actinobacteria .06 .8

As you can see there is significantly more Proteaobacteria in the CHF Group. When they looked closer the researchers found a marked increase in E Coli and several unclassified species of Enterobacteriacae, Roseburia, Enterococcaceae, and Parabacteroides. There was also an increase in Parabacteroides Distasonis and Bacteroides Uniformis.  

In the healthy dogs there was an increase in unclassified species of Prevotella, Catenibacterium,  Erysipelotrichaceae. There was also an increase Clostridium Cocleatum, and Eubacterium biforme.

There was no statistical difference between the three different groups of those with CHF. It was a small sample size so it is still possible that there was a difference.

There was also an increased presence of E. coli, and Enterococcaceae in dogs with CHF. This is consistent with studies in human patients with heart disease, and could be related to a vulnerable state of the gastrointestinal tract in both species. Metabolic studies have shown that certain genera of Enterococcaceae, E. coli and other related species may be more competitive in conditions of oxidative stress. So it is possible that they were able to thrive as a result of the heart condition.

Only one bacterial species was found to be influenced by dogs eating human food. This was the unclassified species of Catenibacterium a member of the Erysipelotrichaceae family. In dogs with CHF there was a decrease in abundance. The significance of the loss of Erysipelotrichaceae with CHF is however unknown.


The Researchers concluded that dogs with CHF have quantifiable dysbiosis with an increase in abundance of Proteobacteria (Enterobacteriaceae and E. coli). This was a small sample size, but it does raise the question about whether Dysbiosis contribute to the heart disease, or whether the heart disease was a contributing factor in causing dysbiosis.

Gastric Dilatation-Volvulus (Bloat)

This study took fecal samples from 38 Healthy Great Danes, and 37 dogs with at least one occurrence of Gastric Dilation Volvulus.

There GDV were generally fed more protein 186.5 vs 173.3, fewer carbs 276 vs 301.7, and were older 6.6 vs 4.5. The age at GDV onset was 4.6 years.

Alpha diversity varied between the control and GDV dogs.

Control GDV
3.37 ±0.92 4.1 ±0.65

The Researchers also found significant differences in the abundance of different bacteria phylums between control and GDV dogs.

Phylum Control GDV
Firmicutes 25.68 38.71
Fusobacteria 7.8 6.56
Bacteroidetes 62.98 47.93
Proteobacteria 3.09 5.84
Actinobacteria .14 .49

They found differences in the amount of ten different specific bacteria between control and GDV dogs. These were Collinsella, Prevotella, Lactobacillus, three members of the Clostridales, and three members of the Proteobacteria, including Helicobacteria and Escherichia/Shigella group.

In the dogs with GDV, Collinsella, Lactobacillus, two members of the Peptostreptococcaceae, a member of the Escherichia Shigella group in the Enterobacteriaceae, and another gamma-Proteobacteria were enriched in the microbiome. It is important to note that the Actinobacteria only contained one genera, Collinsella.

In addition, there were significant differences in diversity between control and GDV dogs with at least one risk allele.

More specifically, Actinobacteria were significantly higher in dogs with at least one risk allele in TLR5 and Firmicutes were significantly enriched in dogs with one risk allele in DRB1. 


While genetic factors may be the highest risk factor for Gastric Dilation Volvulus, and environmental factors may also play an important role.

The research suggests that variations in the gut microbiome may predispose dogs to Gastric Dilation Volvulus. They do acknowledge the possibility that previously suffering from GDV (Bloat), may have altered the gut microbiome. They did however limit stool samples to 3 months after any surgery, antibiotic treatments, or symptoms of any gastric issues.

Ultimately no one knows what causes Bloat, and trying to discover the root cause of bloat is almost impossible as it is not something that can be predicted.

Testing this hypothesis would ultimately require a long term study involving thousands of dogs at risk of bloat, and monitoring their gut microbiome over time and seeing if there is any pattern in the dogs that have an occurrence of bloat.

Overall Conclusion

Both studies did find different percentages of the various phylum’s in the dogs gut microbiome. In both studies the dogs with CHF and GCV had higher amounts of Proteobacteria and Actinobacteria than the control groups.

This research is still too early to tell us anything definitively, and the researcher admit as much. The research does demonstrate the need for more long-term studies, with larger sample sizes to see whether the gut microbiome is changed by GDV or Heart disease, or whether dysbiosis helps contribute to Heart Disease and GDV.

Hullar MAJ, Lampe JW, Torok-Storb BJ, Harkey MA. The canine gut microbiome is associated with higher risk of gastric dilatation-volvulus and high risk genetic variants of the immune system. PLoS One. 2018 Jun 11;13(6):e0197686. doi: 10.1371/journal.pone.0197686. PMID: 29889838; PMCID: PMC5995382.

Seo, J., Matthewman, L., Xia, D. et al. The gut microbiome in dogs with congestive heart failure: a pilot study. Sci Rep 10, 13777 (2020).