The Gut Microbiome and It’s Links to Overall Health: Healthy Gut, Healthy Dog

• Dog Physiology, General Health & Wellness, Health Conditions

In ‘The Dog’s Digestive System: Go With Their Gut‘ you read about the anatomical features of a dog’s digestive system in, but what about the physiology? This blog delves into the gut microbiome, and how it affects a dog’s overall health and susceptibility to disease.

What is the Gut Microbiome?

The gut is lined with a mucosal barrier, which assists with the maintenance of host bacteria balance(1). When microbial communities become imbalanced, there can be a negative impact on the normal gut microbiota, and breaching of the intestinal barrier, resulting in gut dysbiosis(2). In a healthy, balanced gut, the commensal bacteria provide the host with resistance to pathogen colonisation, where resident microbes outperform pathogens for resources(3). Commensal bacteria also support all aspects of digestion, from nutrient breakdown, production of short chain fatty acids (SCFAs), and providing energy for both the host and other commensal gut bacteria(4).

The gut microbiota release nutrients and metabolites, which influence immune cells and inflammatory functions(1,5). There are around 1010-1014 microorganisms within the intestines of dogs(6), and between these resident bacteria and host cells there is a symbiotic relationship. Commensal bacteria are important for producing postbiotics such as SCFAs, secondary bile acids (SBAs) and metabolites, the levels of which influence gut health(6). The conversion of primary bile acids (PBAs) to SBAs is very important for modulating the gut microbiota, influencing digestion and potentially impacting overall health(7).

Several factors can influence gut microbe balance and composition, with a pet’s health status being a strong contributor(8). Dietary changes, stress, illness, antibiotics, NSAIDs, and agrichemicals can also affect the balance of the gut microflora. Balance of microbes and pathogens is key to ensure a healthy pet with a strong immune system, after all, 70-80% of immune cells and present in the gut(4). Whilst some are typically associated with enteric diarrhoea, these same pathogens are also found in the gut of healthy animals – thus, it’s all about balance!(3,9). Having a diverse and varied microbe population will ensure healthy digestion, assist in absorption of essential nutrients and regulate the immune, metabolic and nervous systems. Having a good gut biodiversity score can also favour species of good gut bacteria associated with a healthy ageing process, such as F.perfoetens (4,10).

How Gut Health Impacts Overall Health

Food Intolerances and Leaky Gut

Food intolerances often manifest with gut symptoms, and can be mistaken for conditions such as IBD, due to symptom overlap(1). A food intolerance results from the inability to breakdown a certain food substance, and prolonged feeding of this substance can cause a condition known as leaky gut. Leaky gut results in weakening of the usually tight barrier junctions in the intestinal epithelium, allowing the passage of partially digested food molecules (and bacteria) into the bloodstream, where the body may develop an immunological response to them. This is due to triggering of an immune cascade, where these food particles are tagged as invaders(18).

Common symptoms of leaky gut include bloating, flatulence and diarrhoea, and can also cause systemic, non-specific symptoms, such as itching, redness and inflammation. As we know, our dogs do not really ‘chew’ their food due to their lack of lateral jaw movements, thus when consuming a food with a lower digestibility, such as kibble, an extra burden is placed on the digestive system. This burden increases as pets age, and their levels of digestive enzymes naturally decrease.  Treating the root cause of leaky gut is the most effective way to manage it. See our blog on Elimination Diets: Troubleshooting Allergies and Intolerances for guidance.

Heart Health

Several microbial metabolites (TMOA, SBA, SCFA) play an important role in regulating heart function, which indicates that the gut metabolome may be able to regulate the development of cardiovascular diseases(11). Dogs with severe myxomatous mitral valve disease (MMVD) have been found to have a lower concentration of P. hiranonis in the gutcompared to healthy dogs, which is linked to reduced SBAs(11). Additionally, SCFA end products of microbial fibre fermentation may be important in the regulation of MMVD, as dogs diagnosed with the condition had a lower abundance of SCFA producing microbes(11).

See our Guide to Heart Health for additional information on keeping your dog young at heart.

Chronic Kidney Disease (CKD)

Gut dysbiosis in human patients with CKD is associated with an elevated level of uremic toxins, which in turn speeds up the progression of CKD(12). In dogs, specific bacteria species known for their inflammatory effect were found to be overgrown in those suffering from CKD(13). Additionally, in cats with CKD, there was decreased diversity of the faecal microbiome compared to healthy cats(14).

See our blog on Chronic Kidney Disease in Dogs for further insight into the role diet plays into renal health.

Body Condition

Research in dogs found that a higher body condition score (6-8) has a negative effect on the balance and biodiversity of the gut microbiota(10). On the 1-10 scale, a dog with an ideal body condition should sit between 4-5. Thus, in overweight and obese dogs, the commensal gut bacteria are repressed, which allows an increase in the percentage of opportunistic bacteria.

See our blog on Obesity and Diet In Dogs for further information.

Pancreatic Conditions

Certain illnesses can affect the microbiome, such as exocrine pancreatic insufficiency (EPI), where an insufficient number of digestive enzymes are produced, which can cause an abnormal amount of food in the intestinal lumen(15). This issue may also be the result of feeding a diet with poor digestibility or inflammatory diseases. An altered gut microbiome has also been associated with development of diabetes in dogs, with a decline in microbial diversity and reduction in butyrate producing bacteria, compared to healthy animals(16). This is significant, as butyrate is a SCFA produced during fibre fermentation in the gut, which is known to benefit digestive health through its anti-inflammatory and antineoplastic properties(17).

Behaviour

Research has also shown that raw fed dogs have higher faecal levels of gamma-aminobutyric acid (GABA), an important inhibitory neurotransmitter which decreases certain activity in the brain and exerts a calming effect(8). It could also be considered a postbiotic mediator of the gut-brain axis. Decreased GABA levels are implicated in the pathophysiology of hyperactivity, depression, and anxiety disorders(18).

Further Information On Gut Health

See our gut health chapters linked below:

  1. The Dog’s Digestive System: Go With Their Gut
  2. The Gut Microbiome and It’s Links to Overall Health: Healthy Gut, Healthy Dog
  3. Common Gut Conditions in Dogs
  4. How Diet Impacts Gut Health: Food For Thought

References

  1. Wernimont, S. M. et al. (2020) ‘The Effects of Nutrition on the Gastrointestinal Microbiome of Cats and Dogs: Impact on Health and Disease,’ Frontiers in Microbiology, 25(11), 1266. Available here
  2. Stavropoulou. E. et al. (2021) ‘Focus on the Gut–Kidney Axis in Health and Disease,’ Frontiers in Medicine, 21(7), 620102. Available here
  3. Blake, A. B. and Suchodolski, J. S. (2016) ‘Importance of gut microbiota for the health and disease of dogs and cats,’ Animal Frontiers, 6(3), 37-42. Available here 
  4. Hughes, C. (2023) ‘The role of gut microbiology in veterinary science,’ Improve Veterinary Practice. Available here
  5. Tizard, I. R. and Jones, S. W. ‘The Microbiota Regulates Immunity and Immunologic Diseases in Dogs and Cats,’ Veterinary Clinics of North America: Small Animal Practice, 48(2), 307-322. Available here
  6. Atuahene, D. et al. (2024) ‘Gut Health Optimization in Canines and Felines: Exploring the Role of Probiotics and Nutraceuticals,’ Pets, 1(2), 135-151. Available here
  7. Herstad, M. V. et al. (2017) ‘A diet change from dry food to beef induces reversible changes on the faecal microbiota in healthy, adult client-owned dogs,’ BMC Veterinary Research, 13(147). Available here
  8. Schmidt, M. et al. (2018) ‘The fecal microbiome and metabolome differs between dogs fed Bones and Raw Food (BARF) diets and dogs fed commercial diets.’ PLoS One, 13(8), 0201279. Available here
  9. Marks, S. L. et al. (2011) ‘Enteropathogenic Bacteria in Dogs and Cats: Diagnosis, Epidemiology, Treatment, and Control,’ Journal of Veterinary Internal Medicine, 25(6), 1195-1208. Available here
  10. You, I. and Kim, M. J. (2021) ‘Comparison of Gut Microbiota of 96 Healthy Dogs by Individual Traits: Breed, Age, and Body Condition Score,’ Animals, 11(8), 2432. Available here
  11. Rindels, J. E. and Loman, B. R. (2024) ‘Gut microbiome – the key to our pets’ health and happiness?’ Animal Frontiers, 14(3), 46-53. Available here
  12. Khiabani, S. A. et al. (2023) ‘chronic kidney disease and gut microbiota,’ Heliyon, 9(8), 18991. Available here
  13. Kim, K. et al. (2023) ‘A pilot study of alterations of the gut microbiome in canine chronic kidney disease,’ Frontiers in Veterinary Science, 10,1241215. Available here
  14. Summers, S. C. et al. (2019) ‘The faecal microbiome and serum concentrations of indoxyl sulfate and p-cresol sulfate in cats with chronic kidney disease,’ Journal of Veterinary Internal Medicine, 33(2), 662-669. Available here
  15. Suchodolski, J. S. ‘Analysis of the gut microbiome in dogs and cats,’ Veterinary Clinical Pathology, 50(1), 6-17. Available here
  16. Kieler, I. N. et al. (2019) ‘Diabetic cats have decreased gut microbial diversity and a lack of butyrate producing bacteria,’ Scientific Reports, 9, 4822. Available here
  17. Goncalves, P. and Martel, F. (2013) ‘Butyrate and Colorectal Cancer: The Role of Butyrate Transport,’ Current Drug Metabolism, 14, 994-1008. Available here
  18. Brady, C. (2021) Feeding Dogs: The Science Behind The Dry Versus Raw Debate

Lucy James, BSc (Hons) Bioveterinary Science

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