Similar to humans, the gut microbiota of dogs is a diverse and dynamic community of microorganisms that plays a vital role in maintaining health. It contributes significantly to metabolism, immune function, and resistance to disease. In recent years, research has increasingly focused on understanding the composition and development of the canine gut microbiota, the factors that influence it, and potential interventions to support or restore gut health.
The dominant bacterial phyla in the dog gut include Firmicutes, Bacteroidota, Fusobacteriota, Pseudomonadota, and Actinomycetota. These groups are consistently present in healthy dogs, although their relative abundance can vary depending on individual characteristics and environmental conditions (Huang et al., 2020; You & Kim, 2021).
But what does this actually mean? What specific roles do these bacterial phyla play in the canine gut?
Let’s see what’s going on under the surface!
- Firmicutes: Representing the most dominant phylum in the canine gut microbiota, Firmicutes includes the highly diverse and abundant class Clostridia. A key function of these bacteria is the synthesis of butyrate, a short-chain fatty acid that serves as a primary energy source for colonocytes and supports intestinal health (Garrigues et al., 2022).
- Bacteroidota: Representing the second most abundant phylum in the canine gut, Bacteroidota includes members of the genus Bacteroides, which are particularly noteworthy for their capacity to metabolize glycans and interact with host gut tissues. This interaction not only contributes to the host’s defense against pathogenic microorganisms but also supports the nutritional requirements of other microbial populations within the gut ecosystem (Garrigues et al., 2022).
- Fusobacteriota: This phylum is predominantly represented by the genus Fusobacterium, which constitutes approximately 20% of the total microbial population in the canine gut. These bacteria are particularly efficient at degrading proteins into amino acids and peptides, thereby playing a pivotal role in protein metabolism—especially in carnivorous species (Garrigues et al., 2022).
- Pseudomonadota: This phylum plays a multifaceted role in the canine gut, contributing to essential metabolic processes such as the degradation of proteins, carbohydrates, and vitamins. Additionally, it supports the maintenance of an anaerobic environment, which is critical for sustaining gut homeostasis (Garrigues et al., 2022).
- Actinomycetota: Although this phylum constitutes the least abundant group in the adult canine gut microbiota—approximately 4%—emerging research suggests it may have implications for cognitive health. Lower levels of Actinomycetota, as observed in healthy dogs, have been associated with enhanced memory performance, indicating a potential link between this microbial group and cognitive aging processes (Kubinyi et al., 2020). These findings highlight that not only the presence of specific microbial taxa but also their relative abundance may be critical to host health.
Several factors contribute to the varying abundance of these phyla—here are the key drivers:
- Age is a significant determinant of gut microbiota composition in dogs, with notable shifts occurring throughout the lifespan. In older dogs, certain bacterial taxa such as Fusobacterium perfoetens (an opportunistic pathogen associated with intestinal diseases) tend to be more prevalent (You & Kim, 2021). Conversely, the gut microbiota of puppies undergoes rapid development, shaped by maternal transmission, environmental exposure, and host-specific factors. Early colonization by anaerobic bacteria is particularly critical for healthy physiological development, and disruptions during this formative period can predispose puppies to metabolic and gastrointestinal disorders (Garrigues et al., 2022).
- Body weight and diet are closely linked to variations in the canine gut microbiota. Overweight dogs have been shown to harbor higher levels of Fusobacteriota, particularly F. perfoetens, indicating a potential microbial signature associated with excess body weight (Chun et al., 2020). In addition to body condition, the composition of the diet—especially the presence and type of dietary fiber—plays a crucial role in shaping the gut microbial community. Fiber influences the abundance and activity of specific microbial taxa, thereby affecting overall gut health and metabolic function (Panasevich et al., 2015).
- Health status is widely recognized as a key determinant of the composition and diversity of the canine fecal microbiome. Dogs affected by medical conditions such as exocrine pancreatic insufficiency (EPI) and inflammatory bowel disease (IBD) exhibit distinct microbial profiles compared to healthy individuals. These conditions are associated with significant structural alterations and a marked reduction in microbial diversity, highlighting the impact of disease on gut microbial homeostasis; for example IBD dogs showed decreased abundance of Bacteroidota (Isaiah et al., 2017; Minamoto et al., 2015). In addition to disease, other health-related factors—such as medication use—also play a critical role in shaping the gut microbiota. For instance, antibiotic administration can lead to profound disruptions in microbial composition, characterized by a loss of richness and diversity, with some changes persisting long after treatment ends (Schmid & Tolbert, 2024; You & Kim, 2021).
✨ Coming Up Next! ✨
We’re just getting started. In the upcoming posts, we’ll explore how different diets shape your dog’s gut microbiota, dive into the science behind prebiotics and probiotics, and uncover practical tips to boost your pup’s digestive health.
🐾 Stay tuned—there’s a lot more to discover!
REFERENCES
Chun, J., Ji, S., Lee, S., Lee, Y., Kim, B., & Kim, K. (2020). Difference of gut microbiota composition based on the body condition scores in dogs. Journal of Animal Science and Technology, 62(2), 239–246. https://doi.org/10.5187/jast.2020.62.2.239
Garrigues, Q., Apper, E., Chastant, S., & Mila, H. (2022). Gut microbiota development in the growing dog: A dynamic process influenced by maternal, environmental and host factors. Frontiers in Veterinary Science, 9, 964649. https://doi.org/10.3389/fvets.2022.964649
Huang, Z., Pan, Z., Yang, R., Bi, Y., & Xiong, X. (2020). The canine gastrointestinal microbiota: Early studies and research frontiers. Gut Microbes, 11(3), 635–654. https://doi.org/10.1080/19490976.2019.1704142
Isaiah, A., Parambeth, J. C., Steiner, J. M., Lidbury, J. A., & Suchodolski, J. S. (2017). The fecal microbiome of dogs with exocrine pancreatic insufficiency. Anaerobe, 45, 50–58. https://doi.org/10.1016/j.anaerobe.2017.02.010
Kubinyi, E., Rhali, S., Sándor, S., Szabó, A., & Felföldi, T. (2020). Gut microbiome composition is associated with age and memory performance in pet dogs. Animals, 10(9), 1488. https://doi.org/10.3390/ani10091488
Minamoto, Y., Otoni, C. C., Steelman, S. M., Büyükleblebici, O., Steiner, J. M., Jergens, A. E., & Suchodolski, J. S. (2015). Alteration of the fecal microbiota and serum metabolite profiles in dogs with idiopathic inflammatory bowel disease. Gut Microbes, 6(1), 33–47. https://doi.org/10.1080/19490976.2014.997612
Panasevich, M. R., Kerr, K. R., Dilger, R. N., Fahey, G. C., Jr., Guérin-Deremaux, L., Lynch, G. L., Wils, D., Suchodolski, J. S., Steer, J. M., Dowd, S. E., & Swanson, K. S. (2015). Modulation of the faecal microbiome of healthy adult dogs by inclusion of potato fibre in the diet. British Journal of Nutrition, 113(1), 125–133. https://doi.org/10.1017/S0007114514003274
Schmid, S. M., & Tolbert, M. K. (2024). Harnessing the microbiome: Probiotics, antibiotics and their role in canine and feline gastrointestinal disease. The Veterinary Record, 195(S2), 13–25. https://doi.org/10.1002/vetr.4915
You, I., & Kim, M. (2021). Comparison of gut microbiota of 96 healthy dogs by individual traits: Breed, age, and body condition score. Animals, 11(8), 2432. https://doi.org/10.3390/ani11082432