Gastrointestinal (GI) ulcers in dogs are more than just a localized wound in the stomach or intestinal lining. They represent a significant disruption to the entire digestive ecosystem — and the ripple effects on the gut microbiota can complicate healing and long-term health. As veterinary professionals, understanding this relationship opens the door to more comprehensive, integrative treatment strategies.

How GI Ulcers Disrupt the Gut Microbiota

The GI tract houses an estimated 70-90% of the immune system, and the gut microbiome plays a central role in maintaining that immune competence. When ulceration occurs — whether from NSAIDs, corticosteroids, Helicobacter infection, mast cell tumors, or hypoadrenocorticism — the mucosal barrier is compromised. This breach disrupts the delicate balance between beneficial and pathogenic bacterial populations.

Key microbiome disruptions seen with GI ulceration include:

• Dysbiosis — a shift away from commensal bacteria such as Lactobacillus and Bifidobacterium species toward potentially pathogenic organisms
• Reduced short-chain fatty acid (SCFA) production — SCFAs like butyrate are essential for colonocyte health and mucosal repair
• Increased intestinal permeability — sometimes called “leaky gut,” this allows bacterial translocation and systemic immune activation
• Altered local pH — ulcer-related bleeding and acid dysregulation further stress microbial communities

A study by Suchodolski et al. (2012) in PLOS ONE demonstrated that dogs with chronic GI disease showed significant reductions in Faecalibacterium species — bacteria known for their anti-inflammatory properties. This dysbiosis can both result from and perpetuate mucosal damage, creating a difficult cycle to break.

Conventional Treatment: The Foundation

Before integrative strategies are layered in, conventional management remains the cornerstone. Standard of care typically includes:

• Proton pump inhibitors (PPIs) such as omeprazole to reduce gastric acid
• H2 receptor antagonists as an adjunct acid-reducing strategy
• Sucralfate for mucosal coating and cytoprotection
• Addressing the underlying cause — removing offending drugs, treating neoplasia, or managing hypoadrenocorticism

It is critical to identify and eliminate the primary etiology before any integrative approach will be fully effective.

Integrative Strategies to Support Microbiome Recovery

1. Probiotics

Probiotic supplementation is one of the most evidence-supported integrative tools available. Enterococcus faecium (strain SF68) and Bifidobacterium animalis (strain AHC7) have demonstrated efficacy in canine GI disease. Products such as Fortiflora and Proviable have published efficacy studies supporting their use. Probiotics help normalize intestinal pH, compete against pathogenic bacteria, and support SCFA production — all critical to ulcer healing and microbiome restoration.

Prebiotics — fermentable dietary fibers — feed beneficial bacteria and support their repopulation. Fructooligosaccharides (FOS) and psyllium are commonly used in clinical practice to support microbiome diversity.

A highly digestible, low-fat, novel protein or hydrolyzed protein diet reduces the antigenic load on an already stressed GI system. Reducing dietary fat decreases gastric acid secretion and supports mucosal healing.

Fish oil supplementation provides EPA and DHA, which have demonstrated anti-inflammatory effects on the GI mucosa. Care should be taken to source products free of heavy metal contamination.

While robust canine clinical trials are limited, slippery elm bark (Ulmus rubra) has been used traditionally as a mucosal demulcent. L-glutamine is an amino acid that serves as a primary fuel source for enterocytes and may support mucosal barrier repair.

References

• Suchodolski JS, et al. (2012). The fecal microbiome in dogs with acute diarrhea and idiopathic inflammatory bowel disease. PLOS ONE.
• Marks SL, et al. (2011). Enteropathogenic bacteria in dogs and cats. Journal of Veterinary Internal Medicine.