Gastrointestinal Disease: What the Research Says
Evidence from 24 peer-reviewed studies
What Professionals Should Know
- •Do not routinely recommend probiotic supplements to improve digestive efficiency or prevent common gastrointestinal conditions like colic or salmonellosis in horses
- •Exercise caution with high-dose novel probiotic products, as they may worsen diarrhea rather than improve it
- •Consider multistrain probiotic formulations for performance horses where improved stamina and aerobic fitness are goals, though evidence remains limited
- •Gradual transitions when changing feed and careful management of housing changes are critical preventative strategies, as these are the most evidence-supported modifiable risk factors for colic
- •Owners and managers should implement standardized protocols for any management changes (feed, housing, exercise, water access, carer changes) to minimize colic risk
- •While other risk factors exist, focus preventative efforts on feed and housing management where the strongest evidence base exists
- •If you need to screen foals for abdominal disease, the FOCUS protocol offers a practical time-efficient alternative (median 7 minutes) suitable for emergency situations where speed matters
- •You don't need extensive ultrasound experience to perform these protocols—even clinicians with limited US training achieved good results, making this accessible to most equine practices
- •In stable settings with healthy foals, the more comprehensive 12-window FUS protocol provides better diagnostic coverage; reserve the 7-window FOCUS for emergency cases where single-position imaging is needed
- •Do not rely on ABE alone as a diagnostic or prognostic tool when evaluating colic cases—continue using established clinical and laboratory assessment protocols
- •Recognize that despite extensive research, no single blood marker exists that can definitively predict which colic cases need surgery or how they will progress, so comprehensive clinical evaluation remains essential
- •Consider ABE as part of a broader metabolic assessment rather than a standalone decision-making tool for surgical vs. medical management
- •In emergency settings where cortisol testing is unavailable, eosinophil counts from routine blood work may help predict survival outcomes in horses with abdominal pain—lower counts suggest poorer prognosis
- •Severely stressed horses presenting with abdominal pain typically show both elevated cortisol and eosinopenia; these findings together support a stress leukogram pattern
- •While promising, eosinophil count should not yet replace clinical judgment or other diagnostic parameters; further validation is needed before routine prognostic application
- •When evaluating colic cases, particularly during summer months, watch for fever and elevated lactate as red flags for potential Salmonella shedding, allowing earlier implementation of isolation protocols
- •Development of reflux or persistent fever during hospitalization for colic should heighten suspicion for Salmonella shedding and prompt appropriate biosecurity measures to protect other horses and staff
- •Although Salmonella shedding prevalence in colic populations is relatively low (3.5%), identifying high-risk cases through clinical predictors enables targeted and effective barrier nursing without unnecessary blanket precautions
- •D-dimer can be used as a prognostic marker in critically ill horses, but practitioners should understand that current assays are human-derived and their reliability in horses varies
- •Elevation of d-dimer correlates with systemic inflammation and thrombotic disease severity; clinicians should consider which assay is being used when interpreting results
- •Until equine-specific d-dimer assays are available, understanding the limitations and comparative performance of human assays is essential for appropriate clinical interpretation in horses with colic and systemic disease
- •Implement fecal egg count testing and specific S. vulgaris diagnostics (PCR and serology) as standard practice rather than routine deworming; high seropositivity suggests widespread exposure that needs targeted management
- •Consider S. vulgaris as a differential diagnosis in horses with peritonitis, particularly given rising concerns about this parasite in Sweden since prescription-only anthelmintics were implemented
- •Educate clients on pasture management strategies to reduce parasitic burden, as this appears to be a significant knowledge gap; rotation systems and fecal monitoring should be prioritized over blanket deworming protocols
- •Colic in horses is associated with dysbiosis (reduced bacterial diversity and altered microbial composition), suggesting microbiota analysis may help understand colic pathophysiology
- •Loss of beneficial commensal bacteria and overgrowth of potentially pathogenic organisms in colic cases suggests microbiota modulation (probiotics, prebiotics) could be investigated as therapeutic targets
- •Faecal microbiota profiling could potentially become a diagnostic or prognostic tool for colic, though larger studies across different colic types are needed before clinical application
- •Surgeons can confidently choose either sutured or stapled anastomosis technique for large colon resection based on individual case factors and surgeon preference, as both yield equivalent survival outcomes
- •Expected hospitalization averages 9 days regardless of anastomosis method; counsel owners accordingly for planning and costs
- •Both prophylactic and salvage colectomies showed similar outcomes, suggesting technique rather than indication is the relevant surgical variable
- •When selecting colloid fluid therapy for hypoprotemic horses with GI disease, compare HES formulation options for their specific effects on maintaining colloid osmotic pressure and acid-base status
- •Understanding colloid formulation differences helps optimize supportive care protocols in acute GI disease cases where plasma volume and protein support are critical
- •Do not interpret elevated blood lactate concentrations in ponies and miniature horses with colic the same way as in large breed horses—breed-specific reference ranges may be needed to avoid false suspicion of surgical lesions or poor prognosis
- •Ponies with GI disease consistently show higher vital signs (respiratory rate, temperature) and higher lactate levels as normal variants; use these as context when assessing colic severity and treatment decisions
- •Blood lactate concentration alone is less predictive of outcome in ponies compared to horses, so rely on additional clinical and diagnostic parameters when determining whether surgery is indicated
- •Parenteral nutrition can be used as supportive care in horses with severe gastrointestinal disease, but its direct benefit on survival remains unclear due to disease heterogeneity—prospective studies are needed to establish clear selection criteria
- •Monitor for hyperglycaemia as the most common PN complication; ensure adequate vitamin supplementation as survivors had higher vitamin content in their PN solutions
- •Consider disease type when formulating PN: inflammatory conditions may benefit from higher glucose infusion rates and vitamins, while obstructive cases may require different lipid and glucose protocols
- •Verify herbicide application rates on pastures where horses graze; even small overdoses of MSMA can cause serious poisoning with high mortality rates
- •Suspect arsenic toxicity in horses presenting with gastrointestinal, vascular, or renal signs after pasture herbicide application; confirm via arsenic levels in kidney, liver, or faecal samples
- •Ensure strict coordination between farm managers and veterinarians before any pesticide or herbicide application on horse pastures to prevent accidental overdosing
- •Medical management with appropriate analgesics, antispasmodics, and supportive care is the most effective first-line treatment for colic in your practice
- •Reserve surgical intervention for cases that fail to respond to medical management, as surgery alone shows poor outcomes without concurrent medical support
- •Implement comprehensive fluid therapy combined with antibiotic coverage alongside pain management and antispasmodic drugs for best results
- •Renal lipidosis should be considered a postmortem finding in donkeys, ponies, and miniature horses presenting with concurrent hepatic lipidosis and gastrointestinal or neurologic signs
- •Elevated lactate and GGT at admission may be markers associated with concurrent renal involvement in equids with suspected hepatic lipidosis
- •The clinical significance of renal lipidosis in living equids remains unknown; further research is needed to determine if antemortem diagnosis and intervention are possible or beneficial
- •Fecal microbiota composition and diversity serve as useful biomarkers for monitoring gastrointestinal health in reintroduced wild equines during adaptation periods
- •Elevated stress hormones (cortisol) and immune markers (IgA) alongside dysbiosis may indicate subclinical or clinical diarrhea requiring intervention
- •Supporting beneficial short-chain fatty acid-producing bacteria through dietary management may help prevent or resolve diarrhea in recently released wild horses
- •CAT and plasma-TEG offer new diagnostic tools to assess coagulation status in critically ill horses with GI disease beyond traditional coagulation tests
- •These global hemostatic assays can differentiate hemostatic aberrations between healthy horses and those with mild versus severe GI complications
- •Consider implementing these tests in critical cases to guide therapeutic decisions and monitor treatment response in horses with gastrointestinal disease
- •Do not rely on any single diagnostic test for IBD—use multiple tests (biopsies and metabolic screening) together to build a diagnosis
- •Both duodenal and rectal biopsies should be considered as part of the diagnostic workup, along with glucose tolerance testing
- •Treatment decisions in IBD cases should be informed by the pattern of results across multiple diagnostic modalities rather than one test alone
- •The VSPro offers a clinically reliable benchtop option for measuring plasma fibrinogen in hospitalized horses, enabling rapid assessment of inflammatory status without sending samples to reference laboratories
- •With strong correlation to reference methods and acceptable precision (7-15% CV), results can be confidently used to monitor horses with gastrointestinal or other inflammatory diseases in clinical practice
- •The minimal bias suggests VSPro measurements are directly comparable to standard laboratory results, making it suitable for serial monitoring and clinical decision-making in real-time
- •This research establishes a reliable method for studying equine intestinal barrier function in vitro, which could improve development of treatments for common GI diseases in horses
- •The ability to culture organoids from different intestinal segments allows region-specific investigation of barrier dysfunction and disease mechanisms
- •These organoid models may accelerate drug testing and therapeutic development for equine colic and other GI conditions without extensive in vivo testing
- •This in vitro model offers a new tool for researchers to test potential colic treatments before equine trials, potentially accelerating development of novel therapeutics for this leading cause of equine mortality.
- •The characterization of normal equine intestinal barrier function provides baseline parameters that could help identify mechanisms of barrier dysfunction in colic and post-surgical complications.
- •Understanding intestinal epithelial restitution mechanisms may inform future nutritional or pharmaceutical interventions to support recovery in horses with gastrointestinal disease.
- •Consider firocoxib as an alternative to flunixin for horses with surgical colic, particularly those with severe gastrointestinal disease, to reduce risk of NSAID-related complications
- •Understand the pharmacological difference: COX-2-selective drugs reduce inflammation and pain while preserving the protective gastrointestinal and renal functions provided by COX-1
- •Challenge established protocols—emerging evidence suggests firocoxib may offer superior safety margins in colic cases despite flunixin's entrenched use in equine practice
- •Scintigraphy offers diagnostic capability beyond bone imaging for investigating soft tissue, organ, and vascular disease when conventional imaging is inconclusive
- •Clinicians should request well-validated non-skeletal scintigraphic protocols and be cautious interpreting results from techniques lacking prospective validation studies
- •Economic and clinical value of non-skeletal scintigraphy varies by technique; seek evidence-based guidance before committing to these investigations
Key Research Findings
No clear benefits for probiotic supplementation to improve starch and fiber digestion in horses
No evidence supporting probiotics for colic treatment or salmonellosis prevention
Conflicting results observed for management of scouring in neonatal foals
High doses of novel probiotic species may exacerbate diarrhea and cause adverse events
Multistrain probiotic formulations showed promise for improving aerobic fitness and stamina in exercising horses
Scoping review identified 58 studies with 22 categories of risk factors grouped into horse-related, management-related, and environment-related factors
Systematic review of management changes identified 14 studies (1 cohort, 8 case-control, 5 cross-sectional) showing feed changes and housing changes as largest bodies of evidence for increased colic risk
Feed changes (5/14 publications) and recent housing changes (3/14 publications) were the most frequently studied modifiable risk factors associated with colic
Most included studies (8/14) did not adequately address confounding factors, and marked heterogeneity in study methodologies limited evidence synthesis
A 12-window Focused US (FUS) protocol was successfully developed and demonstrated good feasibility in assessing healthy (n=17) and sick (n=23) foals, with high diagnostic usefulness for gastrointestinal disease and peritoneal effusions
A shortened FOCUS protocol using 7 windows from single right recumbency achieved significantly faster acquisition time (median 7 min, range 3-10 min) compared to FUS
FUS protocol can be performed by veterinarians with limited ultrasound experience, though clinical constraints in emergency settings may limit applicability
FOCUS protocol showed promise in preliminary testing (n=6) but requires further validation before widespread recommendation in clinical practice
Alactic base excess (ABE) does not reliably distinguish surgical from medical colic in horses
ABE is not a sensitive or specific biomarker for predicting mortality in equine colic cases
Evidence Base
The Safety, Tolerability and Efficacy of Probiotic Bacteria for Equine Use.
Cooke C Giselle, Gibb Zamira, Harnett Joanna E (2021) — Journal of equine veterinary science
Risk factors for acute abdominal pain (colic) in the adult horse: A scoping review of risk factors, and a systematic review of the effect of management-related changes.
Curtis Laila, Burford John H, England Gary C W et al. (2019) — PloS one
Development and application of a focused ultrasound protocol in neonatal foals.
Ellero Nicola, Maggi Alessandra, Busoni Valeria et al. (2026) — Veterinary journal (London, England : 1997)
Alactic base excess is not a sensitive or specific diagnostic tool for outcome in horses with colic.
Crosby Corinne E, O'Connor Annette, Munsterman Amelia S (2025) — Frontiers in veterinary science
Association between Eosinophil Count and Cortisol Concentrations in Equids Admitted in the Emergency Unit with Abdominal Pain.
Villalba-Orero María, Contreras-Aguilar María Dolores, Cerón Jose Joaquín et al. (2024) — Animals : an open access journal from MDPI
Prevalence of and risk factors associated with Salmonella shedding among equids presented to a veterinary teaching hospital for colic (2013-2018).
Kilcoyne Isabelle, Magdesian K Gary, Guerra Margherita et al. (2023) — Equine veterinary journal
Investigation of two different human d-dimer assays in the horse.
Honoré Marie Louise, Pihl Tina H, Busk-Anderson Tanne M et al. (2022) — BMC veterinary research
Parasite Occurrence and Parasite Management in Swedish Horses Presenting with Gastrointestinal Disease-A Case-Control Study.
Hedberg-Alm Ylva, Penell Johanna, Riihimäki Miia et al. (2020) — Animals : an open access journal from MDPI
Differences in the equine faecal microbiota between horses presenting to a tertiary referral hospital for colic compared with an elective surgical procedure.
Stewart H L, Southwood L L, Indugu N et al. (2019) — Equine veterinary journal
Technique-associated outcomes in horses following large colon resection.
Pezzanite Lynn M, Hackett Eileen S (2017) — Veterinary surgery : VS
The effect of colloid formulation on colloid osmotic pressure in horses with naturally occurring gastrointestinal disease.
Bellezzo Fausto, Kuhnmuench Timothy, Hackett Eileen S (2014) — BMC veterinary research
Blood lactate concentrations in ponies and miniature horses with gastrointestinal disease.
Dunkel B, Kapff J E, Naylor R J et al. (2013) — Equine veterinary journal
Parenteral nutrition for horses with gastrointestinal disease: a retrospective study of 79 cases.
Lopes M A F, White N A (2002) — Equine veterinary journal
Outbreak of poisoning by sodium hydrogen methylarsonate (MSMA)-an arsenic-based herbicide-in horses in Brazil.
Pereira Gabriella Faria, Blimbliem Maria Clara Hornich, Machado Anna Laura Previato Rosa et al. (2025) — Equine veterinary journal
DIAGNOSIS AND TREATMENT OF COLIC IN HORSES
Zulkyya Abilova, Zoya Mikniene, Madina Khassanova et al. (2025) — 3i intellect idea innovation - интеллект идея инновация
Renal Lipidosis in Horses and Donkeys: 25 Cases (2008-2022).
Slavik Kali, Bender Susan, Sharkey Leslie et al. (2025) — Journal of veterinary internal medicine
Li Zhenghao, Luo Zhengwei, Hu Defu (2024) — Animals : an open access journal from MDPI
A pilot study evaluating the Calibrated Automated Thrombogram assay and application of plasma-thromboelastography for detection of hemostatic aberrations in horses with gastrointestinal disease.
Honoré Marie Louise, Pihl Tina Holberg, Nielsen Lise Nikolic (2021) — BMC veterinary research
Inflammatory bowel disease (IBD) in horses: a retrospective study exploring the value of different diagnostic approaches.
Boshuizen Berit, Ploeg Margreet, Dewulf Jeroen et al. (2018) — BMC veterinary research
An evaluation of the Abaxis VSPro for the measurement of equine plasma fibrinogen concentrations.
Epstein K L, Brainard B M (2012) — Equine veterinary journal
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Functional and molecular characterization of equine intestinal organoids across media conditions and intestinal segments.
Richardson Lauren M, Gordon Julie, Davila Carlos et al. (2026) — BMC veterinary research
Assessment of equine intestinal epithelial junctional complexes and barrier permeability using a monolayer culture system.
Stewart Amy Stieler, Kopper Jamie J, McKinney-Aguirre Caroline et al. (2024) — Frontiers in veterinary science
Sparing the gut: COX-2 inhibitors herald a new era for treatment of horses with surgical colic.
Ziegler A L, Blikslager A T (2020) — Equine veterinary education
Non-skeletal scintigraphy of the horse: indications and validity.
Archer D C, Cotton J C, Boswell J C (2007) — Veterinary journal (London, England : 1997)