Equine Gastric Ulcer Syndrome (EGUS) is a common term used to describe lesions in the horse’s stomach. Whilst prevalence of EGUS is high in performance horses, even populations of horses that are not working have been found to suffer from this common issue. It is likely that for as long as horses have been around, so has EGUS, however, domestication has certainly increased the prevalence of this issue in horses (Ward et al., 2015).
The horse’s stomach can be divided into two regions: the non-glandular (squamous) region, and the glandular region. These regions are defined by the type of lining that is found there. In the non-glandular region, squamous mucosa lines the stomach and glandular mucosa is found in the glandular region.
The correct name for gastric ulcers found in the squamous region of the stomach is Equine Squamous Gastric Disease (ESGS). ESGD affects the non-glandular, squamous lining of the horse’s stomach. Ulcers in the glandular region are defined as Equine Glandular Gastric Disease (EGGD) and these affect the lower, glandular region of the horse’s stomach.
Did you know? – Diarrhoea in adult horses is not a symptom of gastric ulcers but can be associated with gastric ulceration in foals.
Horses suffering from gastric ulceration have been found to exhibit reduced stride length, poor performance and reduced time to fatigue. Treatment studies have shown improvements after ulcer resolution. However, some horses do not show any symptoms whilst other horses may show extreme symptoms, but on gastroscopy, the severity of the ulcers does not correlate with the level of symptoms seen.
ESGD is caused by exposure to stomach acid and these types of ulcers form quickly. EGGD affects the lower 2/3 of the stomach with glandular ulcers being most frequently found in the antrum (the lowest 1/3 of the stomach). Ulcers in this area form slowly and reflect the failure of the mucous lining (Sykes et al., 2015) that protects the glandular tissue from stomach acid.
Symptoms of Gastric Ulcers in Horses
Many horses who have gastroscopic evidence of ulceration won’t show any symptoms, and therefore, will be considered healthy (Van den Boom, 2022). Despite this, prevalence and severity of ulceration has been found to be higher in horses showing symptoms (Murray et al., 1989).
Observations in horses suffering from EGUS usually include weight loss, poor body condition, and colic. Symptoms specifically associated with ESGD include changes in appetite, slowed eating, and poor performance.
Horses suffering with EGGD have less typical symptoms, for example, an aversion to girthing. However, the symptoms shown do not always correlate with the location of the ulcers as both ESGD and EGGD often occur concurrently (van den Boom 2022).
Prevalence of Gastric Ulcers in Horses
This disease does not solely affect performance horses and all types and populations of horses can suffer from gastric ulcers.
An abattoir study identified that 22% of feral horses suffered with EGUS (Ward, et al. 2015) and studies involving horses participating in university riding programmes found that up to 56% of them had gastric ulcers on endoscopy (Prinsloo et al., 2019). Research in high-level endurance horses has identified that 48% of this population suffer with EGUS and this number increases during the race season (Tamzali et al., 2011).
Whilst over 90% of racehorses are estimated to have gastric ulcers (Bell et al., 2017), the prevalence in non-racing disciplines ranges from 40 -60%.
Gastric Ulcer Diagnosis
Gastroscopy is the only way to diagnose gastric ulceration in horses. Observation of symptoms is an unreliable way to diagnose gastric ulcers and should not be used as a marker for ulcer resolution. A repeat gastroscopy should be performed to confirm ulcer resolution. Gastroscopy also allows grading of the ulceration and will identify the region in which the ulcers are located.
Faecal blood / albumin testing for gastric ulcers is not recommended as bleeding from equine gastric ulcers is not a common or consistent finding (Andrews et al., 2015)
Risk Factors for Ulcers in Horses
Exposure of the squamous region to stomach acid occurs during exercise when the stomach contracts and the acid is forced up from the glandular region to the sensitive tissues in the upper region of the stomach (Lorenzno-Figueras & Merrit 2002). Exercising 5 or more days a week also considerably increases the risk of EGGD (Sykes et al., 2019) and this is thought to be due to altered gastric blood flow or physiological stress (Rendle et al., 2018). However, exercise intensity is not the only risk factor in development of EGGD (Luthersson et al., 2009).
Oral stereotypic behaviours are associated with EGUS however they are considered to be a coping mechanism, rather than a risk factor or direct influence (Sykes et al., 2019).
Risk factors for squamous ulcer formation are daytime forage deprivation (Luthersson et al., 2009), lack of access to water, high starch diets (Widenhouse et al., 2002) and stressful events (Buchanan & Andrews 2003) such as a change in environment, routine or travelling. Lack of contact with other horses has also been identified as a risk factor for the development of Equine Squamous Gastric Disease.
While the reasons why the mucosal lining fails are unknown, physical damage from course forage, ingestion of toxic plants or drugs, or altered mucus constituents due to bacterial or physiological means, are thought to be why ulcers occur in this region.
Heliobacteria pylori plays an important role in the development of gastric ulcers in humans and whilst Heliobacteria-like DNA has been observed in some horses with EGGS, not enough is yet know about bacterial contamination and its link to EGUS (Murray 2003).
Additional risk factors such as lack of social contact, inappropriate use of NSAID’s (Ricord et al., 2021; Whitfield-Cargile et al., 2021) and the number of handlers a horse has (Mönki et al., 2016) have all been identified as playing a role in development of EGUS. The number of handlers was shown to increase EGGD in ridden horses and is thought to be linked to stress.
Treatment for Gastric Ulcers in Horses
Squamous ulcers rarely heal spontaneously and require treatment (Andrews et al., 1999), especially if the horse is still in training. Some spontaneous healing of ulcers has been seen in horses with diet induced ESGD when the causative factors were removed (McGowan et al., 2011). However, lesions are unlikely to heal without medical intervention and healing of ulcers occurs more commonly and more rapidly in horses treated with Omeprazole (Murray et al., 1997).
Treating ESGD with Omeprazole for 28 days has been shown to end with the majority of lesions healing within 21 -28 days. When treating EGGD, higher success rates have been found when combining Omeprazole with sucralfate, a mucosal protectant, which increases the healing rate to 68% when used together for 8 weeks, at least (Sykes et al., 2015).
In recent studies, intramuscular injections of Omeprazole have shown good efficiency with healing rates of 97% (Gough et al., 2020).
EGUS has high recurrence rates and treatment should be accompanied by management changes which reduce the risk factors of EGUS (Buchanan & Andrews, 2003).
Maintaining Digestive Health in Horses
Diets containing additional calcium have been found to reduce the effects of stomach acid on the squamous mucosa (Andrews et al., 2006). Ensuring digestive comfort is essential for horses to thrive and perform at their best. A well-rounded approach to digestive health focuses on supporting the entire gastrointestinal system, from the stomach to the hindgut.
Mineral salts such as calcium carbonate, dicalcium phosphate, magnesium hydroxide, and magnesium carbonate work together with the body to maintain a healthy gastric pH and soothe the stomach's mucosal lining. Ingredients like lecithin, which is highly hydrophobic, and pectin, which forms a gel-like substance when exposed to an acidic environment, can help reinforce the stomach's natural protective mucosa. These components are particularly beneficial for horses on high-concentrate diets or those experiencing stress or other challenges to gastric health (Lo Feudo et al., 2021; van der Boom, 2022).
Support for the microbial population in the hindgut can be enhanced through the use of pre-, pro-, and postbiotics. Prebiotics such as fructooligosaccharides (FOS) and mannan oligosaccharides (MOS) act as food sources for beneficial bacteria, while live yeast (Saccharomyces cerevisiae) promotes fibre fermentation and stabilises the hindgut by encouraging lactate-utilising bacteria (Rossi et al., 1995).
Postbiotics, defined as "inanimate microorganisms and/or their compounds that confer health benefits to the host" (ISAPP Consensus, 2021), are a newer addition to digestive support. These include cell components and metabolites that positively influence gut bacteria, boosting volatile fatty acid production and improving fibre fermentation, particularly in horses on high-fibre, low-calorie diets (Morgan et al., 2007). Studies have shown that horses fed postbiotics also experience a more stable hindgut microbial population and improved immunity (Ganda et al., 2022; Trench et al., 2021).
Further digestive and immune support can come from ingredients like kaolin, which helps bind pathogens, specialised beta glucans that promote gut health, and glutamine, an amino acid that provides energy to immune cells.
By focusing on a balanced diet and targeted nutritional strategies, you can help ensure your horse’s digestive system remains healthy, stable, and ready to support their overall wellbeing.
References
Andrews, F.M., Bernard, W., Byars, D., Cohen, N., Divers, T., MacAllister, A., McGladdery, A., Merritt, A., Murray, M., Orsini, J., et al., 1999. Recommendation for the diagnosis and treatment of equine gastric ulcer syndrome (EGUS). Equine Vet. Educ. 11, 262–272.
Andrews, F.M., Buchanan, B.R., Smith, S.H., Elliott, S.B., Saxton, A.M., 2006. In vitro effects of hydrochloric acid and various concentrations of acetic, propionic, butyric, or valeric acids on bioelectric properties of equine gastric squamous mucosa. Am. J. Vet. Res. 67, 1873–1882.
Andrews, F.M., Camacho-Luna, P., Loftin, P.G., Gaymon, G., Garza Jr., F., Keowen, M.L., Kearney, M.T., 2015. Effect of a pelleted supplement fed during and after Omeprazole treatment on non-glandular gastric ulcer scores and gastric juice pH in horses. Equine Vet. Educ. 28, 196–202.
Buchanan, B.R., Andrews, F.M., 2003. Treatment and prevention of equine gastric ulcer syndrome. Vet. Clin. Equine Pract. 19, 575–597.
Ferrucci, F., Zucca, E., Croci, C., Di Fabio, V. & Ferro, E. (2003). Treatment of gastric ulceration in 10 standardbred racehorses with a pectin-lecithin complex. Veterinary Record, 152: 679-681.
Ganda, E., Chakrabarti, A., Sardi, M., Bobel, J.M., Kozlowicz, B., Norton, S.A., Warren, L.K., & Khafipour, E. (2022). A Postbiotic from Saccharomyces Cerevisiae Fermentation Improves Microbiome Robustness in Young Stress-Challenged Horses in Training. Journal of Animal Science, 100(S3): 292.
Gough, S., Hallowell, G., Rendle, D., 2020. A study investigating the treatment of equine squamous gastric disease with long-acting injectable or oral Omeprazole. Vet. Med. Sci. 6, 235–241.
ISAPP (2021). A roundup of the ISAPP consensus definitions: probiotics, prebiotics, synbiotics, postbiotics and fermented foods. Available at: https://isappscience.org/a-roundup-of-the-isapp-consensus-definitions-probiotics-prebiotics-synbiotics-postbiotics-and-fermented-foods/
Lo Feudo, C.M., Stucchi, L., Conturba, B., Alberti, E., Zucca, E., & Ferrucci, F. (2022). Effects of a nutraceutical supplement in the management of mild equine squamous gastric disease in endurance horses. Vet Record, 189(11): e942.
Lorenzo-Figueras, M., Merritt, A.M., 2002. Effects of exercise on gastric volume and pH in the proximal portion of the stomach of horses. Am. J. Vet. Res. 63, 1481–1487.
Luthersson, N., Nielsen, K.H., Harris, P., Parkin, T.D.H., 2009. Risk factors associated with equine gastric ulceration syndrome (EGUS) in 201 horses in Denmark. Equine Vet. J. 41, 625–630.
McGowan, C., McGowan, T., Andrews, F., Al, Jassim, R., 2011. Induction and recovery of dietary induced gastric ulcers in horses. J. Vet. Intern. Med. 2, 603.
Medina, M., Girard, I.D., Jacotot, E., & Julliand, V. (2002). Effect of a preparation of Saccharomyces cerevisiae on microbial profiles and fermentation patterns in the large intestine of horses fed a high fibre on a high starch diet. Journal of Animal Science, 80: 2600-2609.
Mönki, J., Hewetson, M., Virtala, A.-M.K., 2016. Risk factors for equine gastric glandular disease: a case-control study in a Finnish referral hospital population. J. Vet. Intern. Med. 30, 1270–1275.
Morgan, L.M., Coverdale, J.A., Froetschel, M.A., & Yoon, I. (2007). Effect of Yeast Culture supplementation on Digestibility of Varying Forage Quality in Mature Horses. Journal of Equine Veterinary Science, 27(6): 260-265.
Murray, M.J., 2003 A longitudinal study of Helicobacter antibodies in foals. Proceedings of the 21st American College of Veterinary Internal Medicine, Charlotte, North Carolina, United States, June 4th-7th 2003 p. 415
Murray, M.J., Grodinsky, C., Anderson, C.W., Radue, P.F., Schmidt, G.R., 1989. Gastric ulcers in horses: a comparison of endoscopic findings in horses with and without clinical signs. Equine Vet. J. Suppl. 68–72.
Murray, M.J., Haven, M.L., Eichorn, E.S., Zhang, D., Eagleson, J., Hickey, G.J., 1997. Effects of omeprazole on healing of naturally-occurring gastric ulcers in Thoroughbred racehorses. Equine Vet. J. 29, 425–429.
Prinsloo, M., Hynd, P., Franklin, S., Weaver, S., Van den Boom, R., 2019. Hair cortisol concentration is inversely related to the severity of equine squamous gastric disease. Vet. J. 249, 58–59.
Rendle, D., Bowen, I.M., Brazil, T., Conwell, R., Hallowell, G., Hepburn, R., Hewetson, M., Sykes, B., 2018. Recommendations for the management of equine glandular gastric disease. Equine Vet. J. 2, 1–12.
Ricord, M., Andrews, F.M., Yniguez, ˜ F.J.M., Keowen, M., Garza, F.Jr, Paul, L., Chapman, A., Banse, H.E., 2021. Impact of concurrent treatment with omeprazole on phenylbutazone-induced equine gastric ulcer syndrome (EGUS). Equine Vet. J. 53, 356–363.
Rossi, F., Cocconcelli, P.S., & Masoero, F. (1995). Effect of Saccharomyces cerevisiae culture on growth and lactate utilisation by the ruminal bacterium Megasaphera elsdenii. Annales of Zoologici, 44: 403-409.
Sykes, B.W., Bowen, M., Habershon-Butcher, J.L., Green, M., Hallowell, G.D., 2019. Management factors and clinical implications of glandular and squamous gastric disease in horses. J. Vet. Int. Med. 33, 233–240.
Sykes, B.W., Hewetson, M., Hepburn, R.J., Luthersson, N., Tamzali, Y., 2015. European College of Equine Internal Medicine Consensus Statement—equine gastric ulcer syndrome in adult horses. J. Vet. Int. Med. 29, 1288–1299.
Tamzali, Y., Marguet, C., Priymenko, N., Yazrhi, F., 2011. Prevalence of gastric ulcer syndrome in high-level endurance horses. Equine Vet. Journal 43, 141–144.
Trench, M., Bobel, J.M., Bazurto, C., Dolly, J., Hansen, T.L., Kirk, N., Lopez, C., & Warren, L.K. (2021). Dietary Saccharomyces cerevisiae fermentate affects mucosal immunity in young stress-challenged horses in training. Journal of Equine Veterinary Science, 100: 103503.
van der Boom, R. (2022). Equine gastric ulcer syndrome in adult horses. The Veterinary Journal, 283-284: 105830.
Venner, M., Lauffs, S., & Deegen, E. (1999). Treatment of gastric lesions in horses with pectin-lecithin complex. Equine Veterinary Journal, supplement (29): 91-96.
Ward, S., Sykes, B.W., Brown, H., Bishop, A., Penaluna, L.A., 2015. A comparison of the prevalence of gastric ulceration in feral and domesticated horses in the UK. Equine Vet. Educ. 27, 655–657.
Whitfield-Cargile, C.M., Coleman, M.C., Cohen, N.D., Chamoun-Emanuelli, A.M., Navas DeSolis, C., Tetrault, T., Sowinski, R., Bradbery, A., Much, M., 2021. Effects of phenylbutazone alone or in combination with a nutritional therapeutic on gastric ulcers, intestinal permeability, and fecal microbiota in horses. J. Vet. Int. Med. 35, 1121–1130.