👆 Key points at a glance
- SIBO refers to an unfavourable bacterial overgrowth or imbalance in the small intestine. In pets, it is usually a clue to another digestive problem—not a stand-alone diagnosis.
- For dogs and cats, blood and faecal tests can help narrow down important underlying causes.
- In horses, the focus is usually on hindgut dysbiosis and abnormal fermentation in the caecum and colon. In rabbits and guinea pigs, gastrointestinal stasis is often the central concern. Neither is equivalent to classic small-intestinal SIBO.
- Diet, antibiotics and probiotics are not one-size-fits-all treatments. Veterinary diagnosis and nutrition appropriate for the species are essential.
✔ Medical note: This article explains veterinary topics in plain language. It does not replace a veterinary examination, diagnosis or individual nutritional advice. If acute symptoms occur, seek veterinary care without delay.
SIBO in Pets: What Small-Intestinal Dysbiosis May Mean in Dogs, Cats, Horses and Small Mammals
Gas, diarrhoea, weight loss or a noticeably gurgling abdomen can have many causes in pets. Sometimes the term SIBO comes up—meaning bacterial overgrowth or imbalance in the small intestine. The important point is that, in animals, this is rarely the complete explanation. It is usually more useful to ask why the digestive system has become unbalanced.
1. What does SIBO mean in pets?
2. SIBO in dogs: symptoms and diagnosis
3. Cats: intestine, pancreas and triaditis
4. Horses: hindgut dysbiosis rather than classic SIBO
5. Rabbits and guinea pigs: GI stasis and emergencies
6. Feeding: practical dos and don’ts
7. Treatment: the cause matters
8. Summary
9. FAQs
10. Sources
1. What does SIBO mean in pets?
SIBO is short for 
Small Intestinal Bacterial Overgrowth. It refers to excessive bacterial growth or an unfavourable change in bacterial composition in the small intestine. Put simply, bacteria multiply in the wrong location or in a balance that can interfere with digestion.
In veterinary medicine, the term small-intestinal dysbiosis is often more accurate. The issue may not only be the quantity of bacteria, but also their type and metabolic activity. Gas may be produced, the intestinal lining may be irritated, and nutrients may be absorbed less effectively.
Several mechanisms normally protect the small intestine:
- Stomach acid reduces many organisms taken in through food and water.
- Gut motility moves food and bacteria through the digestive tract.
- The ileocaecal valve acts as a barrier that helps limit backflow between the small and large intestine.
- Bile acids, digestive enzymes, the intestinal lining and the immune system also help maintain balance.
When these protective systems are disrupted, bacteria may shift location or multiply more easily. For this reason, small-intestinal dysbiosis in pets is usually a secondary issue, for example in pancreatic disease, chronic intestinal inflammation, impaired intestinal movement or unsuitable feeding.
Important: do not transfer human protocols to animals
Hydrogen or methane breath tests are commonly used in human medicine. However, they are not standard diagnostic tests in routine veterinary practice for dogs, cats, horses, rabbits or guinea pigs. Do not use human SIBO diets, antibiotics, prebiotics or probiotics without consulting a veterinarian.
2. SIBO in dogs: symptoms and diagnosis
SIBO is mentioned particularly often in dogs. At the same time, the diagnosis is not always clear-cut: many signs can also be caused by parasites, adverse food reactions, chronic enteropathy or pancreatic disease.
Typical signs
- Diarrhoea that recurs over weeks or does not fully resolve
- Weight loss despite a good or unusually large appetite
- Flatulence and noticeably loud intestinal sounds
- Large stool volumes, soft stool or unusually foul-smelling stool
- Signs of nausea, such as lip-smacking, especially in the morning
- Poor use of nutrients from food
Important possible causes
- Exocrine pancreatic insufficiency, or EPI: The pancreas produces too few digestive enzymes. Food is then broken down less effectively, which may alter the intestinal bacterial community.
- Chronic enteropathy: This is an umbrella term for long-lasting intestinal diseases, including dietary reactions and inflammatory conditions.
- Slow intestinal motility: If food remains in the small intestine for longer, bacteria may have more opportunity to multiply.
- Infections or parasites: Intestinal function may take time to recover even after an infection such as giardiasis.
Diagnosis: a sensible pathway
With persistent symptoms, veterinarians do not simply “test for SIBO.” Instead, they work step by step to identify the most likely underlying cause. This usually includes a detailed dietary and medical history, physical examination, faecal testing and blood tests.
- Faecal examination: This can help detect or rule out parasites such as Giardia and worms, as well as other infectious causes.
- TLI testing when EPI is suspected: The test measures trypsin-like immunoreactivity. A low fasting canine TLI value supports a diagnosis of exocrine pancreatic insufficiency in dogs. It reflects blood concentrations of trypsin and especially its precursor, trypsinogen. These substances are produced almost exclusively by the exocrine pancreas. With EPI, much of the functional pancreatic tissue has been lost, so less trypsinogen and fewer digestive enzymes are produced, causing TLI concentrations to decrease.
- Cobalamin and folate: Cobalamin is vitamin B12. Low concentrations may occur with EPI or small-intestinal disease. High folate may be associated with bacterial activity in the small intestine. Both are clues, not stand-alone proof of SIBO.
- cPLI if pancreatitis is suspected: Canine pancreatic lipase immunoreactivity, or cPLI, is a pancreatic marker. It should be interpreted together with clinical signs, examination findings and, when needed, ultrasound; one laboratory value alone cannot establish a diagnosis.
- Faecal microbiome analysis: A dysbiosis index can detect changes in the bacterial community in stool. It reflects dysbiosis in the faecal environment, not bacterial overgrowth in the small intestine. It is an additional piece of information, not a substitute for standard diagnostic work-up.
- Ultrasound or endoscopy: Persistent or severe symptoms may require imaging and, in selected cases, tissue samples.
Scientific literature indicates that indirect markers such as cobalamin and folate cannot reliably confirm or rule out SIBO in dogs on their own. This is why a multi-step diagnostic approach is appropriate.
3. Cats: intestine, pancreas and triaditis
Small-intestinal problems may be less obvious in cats than in dogs. Many cats do not necessarily have marked diarrhoea. Instead, gradual weight loss, recurrent vomiting, reduced appetite or a poor coat may be more noticeable.
One important clinical combination is feline triaditis. This term refers to concurrent inflammatory disease affecting the intestine, pancreas and bile ducts or liver. These conditions can influence each other. For this reason, persistent digestive symptoms in cats should not be prematurely attributed to “gut flora” alone.
Possible signs
- Gradual weight loss
- Recurrent vomiting
- Changes in coat quality or reduced grooming
- Soft, loose or irregular stools
- Reduced activity, withdrawal or altered eating behaviour
Diagnosis in cats
In cats, cobalamin and folate are supportive laboratory markers rather than SIBO tests. If pancreatitis is suspected, the veterinary practice may measure fPLI, or feline pancreatic lipase immunoreactivity. TLI is used in both cats and dogs to assess exocrine pancreatic function, while cPLI and fPLI are species-specific pancreatic lipase tests used as part of the assessment for suspected pancreatitis.
A faecal microbiome analysis can describe dysbiosis in stool, but it cannot independently answer whether bacterial overgrowth is present in the small intestine. Depending on the findings, the diagnostic work-up may include faecal testing, blood tests, ultrasound and, where medically appropriate, tissue samples. In cats especially, the combination of findings is what matters.
4. Horses: hindgut dysbiosis rather than classic SIBO
For horses, “SIBO” is usually not the most appropriate term. Horses are hindgut fermenters: most microbial digestion naturally takes place in the caecum and colon. When bacterial changes arise because of diet or illness, the terms hindgut dysbiosis or abnormal hindgut fermentation are generally more accurate.
If excessive amounts of starch from concentrate feed reach the hindgut, bacteria can ferment that starch rapidly. Acids are produced, pH falls and the microbial balance may shift unfavourably. This mechanism differs from classic human small-intestinal SIBO or the small-intestinal dysbiosis discussed in dogs.
Possible warning signs
- Recurring signs of colic or restlessness
- Reduced performance
- Weight loss or poor feed utilisation
- Free faecal water or noticeable stool changes
- Gas and intestinal sounds
Colic is always an emergency. Free faecal water is not proof of bacterial overgrowth and can have many causes. If a horse has pain, stops eating, sweats, rolls, has a fever or shows circulatory problems, contact a veterinarian immediately.
5. Rabbits and guinea pigs: GI stasis and emergencies
In rabbits and guinea pigs, classic small-intestinal SIBO is also not the most appropriate main explanation. Both species depend on continuous food intake and microbial fermentation in the caecum. In digestive disorders, gastrointestinal stasis, often called GI stasis, is frequently the more relevant concern: gastrointestinal movement slows markedly and, in severe cases, the passage of food can nearly stop.
Reduced food intake, pain, stress, dental disease, unsuitable feeding or inappropriate antibiotics can trigger GI stasis. Food then remains in the digestive tract for longer, gas may accumulate, the gut lining becomes stressed and unfavourable bacteria can multiply. This dangerous cycle can involve the stomach, small intestine, caecum and colon, but it is not the same as classic SIBO.
In rabbits, severe diarrhoea and enterotoxaemia may be associated with overgrowth of Clostridium species. This illustrates why bacterial shifts in the digestive tract should be taken seriously.
Emergency signs
- A bloated or hard abdomen
- Refusal to eat
- Teeth grinding, a hunched posture or marked lethargy
- Very small faecal pellets or no faeces
- Diarrhoea, low body temperature or rapidly increasing weakness
Do not wait: A rabbit or guinea pig with these signs needs immediate veterinary care. Depending on the findings, treatment of GI stasis may include fluid therapy, pain relief, assisted feeding and close monitoring. Before assisted feeding or medication intended to stimulate gut movement is used, a veterinarian must assess whether a mechanical obstruction could be present. A randomly chosen probiotic is not emergency treatment.
6. Feeding: practical dos and don’ts
Nutrition can have a major effect on digestive health. However, it does not replace diagnostics and must fit the species, disease, weight trend and individual tolerance of the animal.
| Species | Dos | Don’ts |
|---|---|---|
| Dog | For chronic signs, discuss a highly digestible gastrointestinal diet or a properly conducted elimination diet using a novel or hydrolysed protein with the veterinary practice. In large-bowel diarrhoea, a fibre-adjusted diet may help depending on the cause and fibre type. | Do not automatically feed “as much fibre as possible.” A very high-fibre diet may not be suitable in dogs with vomiting or small-intestinal diarrhoea. Avoid sudden food changes and do not add unplanned foods or supplements during an elimination diet. |
| Cat | Choose a balanced, well-accepted diet that matches the condition in consultation with the veterinary practice. In unwell cats, adequate energy and nutrient intake, as well as preventing further weight loss, are priorities. | Do not begin an elimination diet or supplement without professional guidance if the cat is already eating poorly or losing weight. A diagnostic elimination diet should be nutritionally complete and veterinary-guided. |
| Horse | Ensure forage is the dietary foundation, review concentrate amounts and divide meals sensibly. A fibre-focused ration adjusted gradually can support a more stable hindgut environment. Make feed changes slowly whenever possible. | Do not feed large single meals of cereal-based or starch-rich concentrate without careful consideration. A cautious guide often used is no more than 1 g of starch per kg of body weight per meal; sensitive horses may need considerably less. The individual ration should be assessed by a qualified professional. |
| Rabbit & guinea pig | Provide good-quality hay at all times and make dietary changes gradually. Loss of appetite, clearly reduced faecal output or abdominal bloating require immediate veterinary assessment. | Do not make sugary or starchy foods the dietary basis. Do not give antibiotics without prescription by a veterinarian experienced with rabbits, guinea pigs or other small mammals. If GI stasis is suspected, do not force-feed or use gut-motility medication without veterinary assessment to rule out obstruction. |
Fibre in dogs: more is not always better
There is no single optimal fibre level for every dog with digestive signs. The right approach depends on the type of symptoms, the suspected cause and the part of the gut affected. With large-bowel diarrhoea, appropriately selected soluble and insoluble fibres may support stool consistency and intestinal movement.
In dogs with vomiting or signs that are more likely to arise from the small intestine, highly digestible, lower-residue diets are often selected. For this reason, high-fibre food or psyllium husk should not be regarded as a general SIBO treatment. The type and amount of fibre should be discussed with the treating veterinary practice.
7. Treatment: the cause matters
There is no universal “SIBO cure” for pets. The appropriate treatment depends on the disease or trigger behind the symptoms.
1. Treat the underlying condition
- With EPI, a dog needs digestive enzyme replacement and suitable monitoring of nutritional status.
- With chronic enteropathy, a targeted elimination diet or hydrolysed-protein diet may be an important early step.
- For horses, adequate forage and review of starch and concentrate feeding are important starting points.
- For rabbits and guinea pigs, emergency care, pain control, fluids and restoration of food intake are key priorities. A possible mechanical obstruction must be assessed by a veterinarian before assisted feeding is used.
2. Use antibiotics selectively
Antibiotics are sometimes necessary, but they are not automatically the right response to diarrhoea or gas. In dogs with chronic enteropathy, they are generally not viewed as the first or only intervention: diet and careful diagnostic work-up are highly important. Unfocused antibiotic use can further alter the gut microbiome and promote antimicrobial resistance.
3. Probiotics and prebiotics: not automatic solutions
Probiotics may be useful in certain situations, but their effect depends on the strain, dose, species and underlying disease. The evidence for dogs and cats with chronic gastrointestinal disease is not sufficiently consistent to mean that every animal should automatically receive a probiotic. Discuss supplements with the treating veterinary practice.
Glossary: simple explanations of key terms
- SIBO
- An unfavourable bacterial increase or shift in the small intestine. In animals, it is often secondary to another condition.
- Dysbiosis
- An imbalance in the gut microbiome. The quantity, composition and function of microorganisms may all change.
- TLI
- Trypsin-like immunoreactivity. A blood test used in dogs and cats to assess exocrine pancreatic function. It is particularly important when EPI is suspected.
- cPLI / fPLI
- Canine or feline pancreatic lipase immunoreactivity. Species-specific blood tests used as part of the overall evaluation when pancreatitis is suspected.
- Cobalamin
- Vitamin B12. Low concentrations in dogs and cats can indicate certain intestinal or pancreatic problems.
- Hindgut dysbiosis
- A disturbance of microorganisms in the caecum and colon. In horses, this term is usually more appropriate than SIBO.
- GI stasis
- A marked slowing of gastrointestinal movement. In rabbits and guinea pigs, it is a serious condition that requires prompt veterinary investigation of the cause.
8. Summary
- Small-intestinal dysbiosis in pets is usually a clue, not a final diagnosis.
- In dogs and cats, TLI, cPLI/fPLI, cobalamin/folate, faecal testing and, if needed, ultrasound can help identify the underlying cause. Microbiome tests can provide additional information but cannot prove small-intestinal SIBO.
- In horses, abnormal fermentation and dysbiosis of the hindgut are the main focus; adequate forage and avoidance of large starch meals are important considerations.
- In rabbits and guinea pigs, GI stasis with abdominal bloating, refusal to eat or absent faecal output is an emergency.
- Antibiotics, probiotics and diets are not universal solutions. Veterinary assessment and treatment of the cause are decisive.
9. FAQs
Can my dog really have SIBO?
Small-intestinal dysbiosis can occur in dogs. However, the symptoms are not specific: EPI, parasites, chronic intestinal disease and dietary reactions can also cause diarrhoea, gas and weight loss. For this reason, diagnosis should not be made from symptoms alone.
What is the difference between TLI and cPLI?
TLI is mainly used to assess exocrine pancreatic function and is important when EPI is suspected. cPLI in dogs and fPLI in cats are pancreatic lipase tests used as part of the overall assessment for suspected pancreatitis.
Can a faecal microbiome analysis diagnose SIBO?
No. A microbiome analysis from stool can provide clues about dysbiosis in the faecal environment. However, it cannot independently prove bacterial overgrowth in the small intestine.
How much fibre does a dog with diarrhoea need?
This depends on the cause, the type of fibre and whether the small or large intestine is mainly affected. A fibre-adjusted diet may help with large-bowel diarrhoea, while a highly digestible, lower-residue diet is often preferred for vomiting or small-intestinal problems. The specific ration should be decided with a veterinarian.
What should I do if my horse has free faecal water or signs of colic?
Free faecal water should be assessed by a veterinarian and through review of feeding management. If there are signs of colic—such as pawing, rolling, sweating, repeatedly lying down or refusing feed—contact the veterinary emergency service immediately.
Is a bloated abdomen in a rabbit an emergency?
Yes. A bloated abdomen, refusal to eat, pain, lethargy or absent faecal output can indicate a severe gastrointestinal disorder. Arrange veterinary care immediately rather than waiting with home remedies. Do not independently use assisted feeding or gut-motility medication until a veterinarian has assessed the rabbit and ruled out a mechanical obstruction.
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10. Sources
- German, A. J., Day, M. J., Ruaux, C. G., Steiner, J. M., Williams, D. A., & Hall, E. J. (2003). Comparison of direct and indirect tests for small intestinal bacterial overgrowth and antibiotic-responsive diarrhea in dogs. Journal of Veterinary Internal Medicine, 17(1), 33–43. Original source via DOI | PubMed
- Rutgers, H. C., Batt, R. M., Elwood, C. M., Lamport, A., & Thomson, H. (1995). Small intestinal bacterial overgrowth in dogs with chronic intestinal disease. Journal of the American Veterinary Medical Association, 206(2), 187–193. Original source at AVMA Journal
- Ruaux, C. G. (2013). Cobalamin in companion animals: Diagnostic marker, deficiency states and therapeutic implications. The Veterinary Journal, 196(2), 145–152. Original source via DOI | PubMed
- Toresson, L., Steiner, J. M., Suchodolski, J. S., Spillmann, T., & Lidbury, J. A. (2019). Review of cobalamin status and disorders of cobalamin metabolism in dogs. Journal of Veterinary Internal Medicine, 33(6), 2491–2502. Original source via DOI
- Texas A&M Gastrointestinal Laboratory. Assays: TLI for exocrine pancreatic function, PLI for pancreatitis, Cobalamin/Folate for small-intestinal function, and Microbiota Dysbiosis Index for canine/feline faecal samples. Original page
- Černá, P., Kilpatrick, S., & Gunn-Moore, D. A. (2020). Feline comorbidities: What do we really know about feline triaditis? Journal of Feline Medicine and Surgery, 22(11), 1047–1067. Original source via DOI | Free full text at PMC
- Richards, N., Hinch, G., & Rowe, J. (2006). The effect of current grain feeding practices on hindgut starch fermentation and acidosis in the Australian racing Thoroughbred. Australian Veterinary Journal, 84(11), 402–407. Original source via DOI | PubMed
- Julliand, V., de Vaux, A., Millet, L., & Fonty, G. (2016). Effect of dietary starch source and concentration on equine fecal microbiota. Journal of Animal Science, 94(8), 3320–3331. Free full text at PMC
- Hassel, D. M., Hill, A. E., & Rorvik, M. M. (2022). Gut health of horses: effects of high fibre vs high starch diet on the gastrointestinal tract and microbiota. BMC Veterinary Research, 18, 323. Free full text at PMC
- Quesenberry, K. E., & Carpenter, J. W. (2013). Gastrointestinal Disease in Guinea Pigs and Rabbits. Veterinary Clinics of North America: Exotic Animal Practice, 16(1), 65–88. Free full text at PMC
- Merck Veterinary Manual. Digestive Disorders of Rabbits. Original page
- World Small Animal Veterinary Association (WSAVA). Global Nutrition Guidelines. Original page
