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The Microbiome’s Influence on Animals' Behavior

Author: DVM Dana Hogg

Analyzing behavior in animals can be a very complex process. Behavioral issues can arise at any point in an animal’s life, and there is not always an immediately identifiable underlying cause. A variety of components, including genetics, environmental and physical stressors, or learned behaviors can influence an animal’s behavior at any time. Behavioral changes in animals can manifest in a variety of different ways, from anxiety, to aggression, to self destructive tendencies.

The microbiome and animals' behaviour

The gut microbiome is critical for healthy digestion, immunomodulation, and metabolism. Research is ever growing in relation to the microbiome and its influence on the central nervous system. Studies have suggested that the microbiome can influence and alter certain behaviors as well as influence the onset of certain neurological diseases. The term “gut-brain axis” has been coined to refer to the guts communication to the central nervous system. The gut brain axis is defined as “inclusive of gut microbiota, gut epithelium, liver, enteric, parasympathetic and sympathetic nervous systems, brain and spinal cord, neuroendocrine connections, metabolites, cytokines, neuropeptides, and signaling molecules” (1) Research in animal models has shown that the microbiome influences cognitive behavior as well as brain biochemistry and function, however, there is still a lot to explore in this field.

Studies on the Microbiome of Distressed Animals

Stress is defined as a normal physiological response to an adjustment or change. A study in mice examined the effects of psychological distress on the microbiota. The mice were exposed to chronic social defeat stress. This stressor caused a change in behavior as well as a reduction in the richness of the microbiome. Additionally, researchers found alterations to cells in the nervous system as well as the immune system. (2)

Aggression and anxiety along with a multitude of behavioral issues are seen frequently in veterinary practices. There is question as to whether animals with certain behavioral issues may have different microbiomes when compared to animals with no behavioral issues. A study analyzed a small group of dogs, half of which were defined as aggressive and the other half which were not. Through analysis of stool samples, it was determined that the microbiome of “aggressive” vs. nonaggressive dogs was in fact different. While it is unclear the exact mechanism by which an alteration in the microbiome influences aggression or vice versa, it does not dispute that there is a correlation between the two and further research should be investigated. (3)

Behavioral concerns in animals strongly impact the human-animal bond and sometimes if left untreated can result in relinquishment of animals. Treatment commonly includes medications, behavioral supplements, as well as behavioral modification plans which are all targeted to the individual. A study in mice examined the effects of supplemental lactic acid bacteria on the microbiome, nervous system, and behavior. They concluded that the addition of Lactobacillus rhamnosus “reduced stress-induced corticosterone and anxiety- and depression related behavior” through studying its impacts on GABA, a main central nervous system neurotransmitter. (4)

While there is still more to investigate on the microbiome, its effects on the central nervous system, and it’s influence on behavior, there is some benefit in considering the addition of probiotics in behavioral therapies in the future.   

Sources
  • Carabotti, Marilia et. al. “The Gut-Brain Axis: Interactions between Enteric Microbiota, Central and Enteric Nervous Systems.” Annals of Gastroenterology, 2016, pp. 203–09. PubMed, www.ncbi.nlm.nih.gov/pmc/articles/PMC4367209.
  • Bharwani, Aadil, et al. “Structural & Functional Consequences of Chronic Psychosocial Stress on the Microbiome & Host.” Psychoneuroendocrinology, vol. 63, 2016, pp. 217–27. Science Direct, www.sciencedirect.com/science/article/abs/pii/S0306453015009348.
  • Kirchoff, Nicole S, et al. “The Gut Microbiome Correlates with Conspecific Aggression in a Small Population of Rescued Dogs(Canis Familiaris).” PeerJ, vol. 7, 2019, p. e6103. Crossref, www.ncbi.nlm.nih.gov/pmc/articles/PMC6330041.. 
  • Bravo, J. A., et al. “Ingestion of Lactobacillus Strain Regulates Emotional Behavior and Central GABA Receptor Expression in a Mouse via the Vagus Nerve.” Proceedings of the National Academy of Sciences, vol. 108, no. 38, 2011, pp. 16050–55. PubMed, www.ncbi.nlm.nih.gov/pmc/articles/PMC3179073.

Dr. Dana Hogg graduated in 2015 from North Carolina State University. She grew up in Wilson, North Carolina. Growing up with several animals, Dr. Hogg was drawn to the field of veterinary medicine at a young age. She completed her undergraduate degree at NCSU in 2009 and her master's degree in 2011.

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