Gastric supplements are a large and growing category, driven by wider awareness of stomach ulcers in horses of every type. They are designed to support the stomach, which is a very different environment from the hindgut targeted by most probiotics. This guide explains how the two differ, outlines equine gastric ulcer syndrome, describes the common ingredients cautiously and sets out when your vet must be involved.
Stomach and hindgut: two different problems
The horse's stomach is small relative to its size, and World Horse Welfare describes it as designed for trickle feeding of forage rather than large meals. It has two distinct linings. The upper squamous region is easily damaged by acid exposure, while the lower glandular region secretes acid and relies on its own protective defences. Chewing forage produces saliva, which BETA notes contains bicarbonate that helps neutralise acidity, and BETA advises giving some fibre before intense exercise to reduce acid splashing onto the upper lining.
The hindgut, by contrast, is a fermentation chamber where microbes break down fibre. Problems there usually relate to sudden diet changes or starch overload, covered in our guide to hindgut health. A product designed for one part of the gut should not be assumed to help the other. Our comparison of a gut balancer vs a gastric supplement sets out the differences.
Equine gastric ulcer syndrome: the basics
The European College of Equine Internal Medicine (ECEIM) published a consensus statement on equine gastric ulcer syndrome (EGUS) in adult horses in 2015. It uses EGUS as an umbrella term and divides it into two conditions.
| Equine squamous gastric disease (ESGD) | Equine glandular gastric disease (EGGD) | |
|---|---|---|
| Location | Upper, non-glandular lining | Lower, glandular lining |
| Main mechanism | Increased acid exposure of an unprotected lining | Less well understood; thought to involve failure of normal defences |
| Evidence on diet and management | Stronger | Weaker |
Signs are not specific
According to the consensus statement, signs associated with ulcers include poor appetite, poor body condition, colic, behaviour changes and poor performance. BETA's owner leaflet adds resistance to girthing, a staring coat and irritable behaviour. None of these signs is specific to ulcers, some horses with ulcers show no signs at all, and the severity seen on gastroscopy does not reliably predict how a horse is affected.
Diagnosis needs gastroscopy
The ECEIM statement describes gastroscopy as the only reliable method of diagnosing gastric ulcers in a living horse, and it does not support diagnosing EGUS from clinical signs alone. Your vet passes an endoscope into the stomach of a sedated horse after a period of fasting. The statement also advises against treating on suspicion without gastroscopy. Treatment is with prescription veterinary medicines chosen by your vet, and squamous and glandular disease often respond differently.
Known risk factors
The consensus statement links squamous disease to high starch or cereal intake, gaps of more than six hours between forage meals, straw as the only forage, intensive or prolonged exercise and lack of constant water access in the paddock. These factors are the reason feeding and management sit at the centre of prevention and recovery.
Where gastric supplements fit
Supplements are feeds, not medicines. Veterinary Medicines Directorate guidance states that non-medicinal products may only be presented as maintaining health in healthy animals, and may not claim to treat or prevent disease. BETA runs a feed assurance mark, developed with the VMD, for feeds suitable for horses prone to gastric ulcers. It applies only to feeds, not supplements, and approved packaging must state that the product does not prevent, treat or cure gastric ulcers. A gastric supplement is best seen as one possible part of a wider plan agreed with your vet, typically alongside or after medical treatment.
Common ingredients, described cautiously
The ECEIM statement reviewed the evidence for several nutritional ingredients. Its overall message is that data are limited and often come from experimental models rather than horses in normal work.
Antacids and buffers
Ingredients such as calcium carbonate, magnesium hydroxide, magnesium oxide or seaweed-derived calcium are included to neutralise acid in the stomach. The consensus statement notes that antacids provide only short-lived relief, of around two hours or less, and that their use as a sole therapy is not justified. Some owners give them shortly before exercise or travel for that reason.
Pectin and lecithin
Pectin and lecithin are thought to strengthen the protective mucus layer. The consensus statement reports that pectin-lecithin experimentally increases mucus in gastric juice, but two studies in fed and fasting models failed to show a protective effect. A combination product containing magnesium hydroxide, pectin-lecithin and live yeast was described as showing promise for both squamous and glandular disease, based on limited data.
Organic acid salts, sea buckthorn and others
The statement described salts of organic acids with B vitamins as possibly beneficial for squamous disease on preliminary evidence, and reported that a sea buckthorn preparation appeared protective against glandular disease in a fasting model. Herbal ingredients such as liquorice, aloe vera and slippery elm also appear in some products; we did not find robust equine trial evidence for them in the sources reviewed for this guide. Anyone competing should check herbal ingredients against BETA NOPS guidance and their governing body's rules.
Feeding and management for ulcer-prone horses
The ECEIM statement and BETA's leaflet give practical guidance that applies to both forms of EGUS.
- Forage. Continuous grazing or ad lib hay is ideal; otherwise provide at least 1.5 kg of forage dry matter per 100 kg bodyweight daily. BETA calculates this as about 8.8 kg of hay or 11.5 kg of haylage for a 500 kg horse. See how much forage a horse needs.
- Starch. Keep cereals to a minimum. The consensus suggests no more than 1 g of starch per kg bodyweight per meal and 2 g per kg per day, with concentrate meals at least six hours apart.
- Fibre before exercise. BETA recommends giving some fibre before intense work to reduce acid splashing, which matters for performance horses.
- Straw. Avoid straw as the only forage source.
- Water and turnout. Make water available at all times and, where appropriate, provide as much turnout as possible.
- Stress. BETA suggests practical steps such as a quieter stable, a companion and feeding horses at the same time.
Choosing a gastric supplement
Gastric supplements are often fed at specific times, for example shortly before exercise, travel or a period when the stomach would otherwise be empty. Check that the product's directions fit your routine, and tell your vet about every product you feed, particularly if your horse is receiving prescription treatment. Keep a simple record of appetite, behaviour under saddle and when the product was given, so any follow-up gastroscopy can be interpreted alongside what you have done.
If your vet agrees a supplement is reasonable, compare products on the active ingredients and their daily amounts, the evidence for that formulation, how the product fits your feeding routine and its cost per day. Be wary of any product that claims to treat, heal or prevent ulcers, which is not permitted for a feed. Our guide on how to choose a horse supplement explains how to read a label, and our desk reviews summarise the published information for individual products.