You have probably heard the rule: never leave a horse without forage for more than four hours at a stretch. In this episode Maartje explains where that rule comes from.

Short answer

A horse produces stomach acid continuously, even when it is not eating. Forage creates chewing, chewing produces saliva, and saliva together with the forage itself helps buffer that acid. If a horse stands too long without forage, acid is left in an empty stomach. That raises the risk of gastric ulcers.

What is the equine digestive system designed for?

Continuous intake of fibre-rich feed. In a natural setting a horse spends up to eighteen hours a day eating. Our horses live a very different lifestyle in many situations – but their digestive systems have not changed with it.

So even a stabled horse needs to be able to eat enough forage, without long gaps in between.

What happens in an empty stomach?

Stomach acid is produced continuously, whether or not the horse is eating. In a grazing horse that acid is constantly diluted and buffered by saliva and by fibre-rich stomach contents. In an empty stomach, neither happens.

One of the problems that can develop as a result is a gastric ulcer. The international consensus statement from the European College of Equine Internal Medicine explicitly names restricted forage availability and long periods without feed as risk factors.

Why should you not train on an empty stomach?

During exercise, abdominal pressure pushes the stomach contents upwards. Stomach acid can then splash onto the upper, less protected part of the stomach lining.

Forage helps in two ways:

• Chewing produces saliva. Saliva helps neutralise stomach acid.
• The forage itself forms a layer in the stomach that helps prevent acid splashing upwards.

So feed a small amount of forage before you train. While grooming and tacking up, for instance – which also happens to be the most practical moment.

What can you do in practice?

1. Spread the forage across the day. Four feeds beat two.
2. Use a slow feeder or a small-holed haynet. Your horse then takes longer over the same quantity, and fewer long gaps appear.
3. Never train on an empty stomach. Give a handful of forage or a forage mix while you get ready.
4. Look at the night. That is usually the longest gap in the 24-hour cycle.

A well-planned forage ration is essential to keeping the digestive system healthy. Most of these changes cost nothing at all – they are about timing rather than quantity.

Frequently asked questions

How long can a horse go without forage? As a rule of thumb, no longer than four hours at a stretch. Shorter gaps are better, including overnight.

Does a slow feeder really help? A net or slow feeder with small openings extends eating time for the same amount of forage. That is precisely the point: not feeding more, but keeping the horse occupied for longer.

How much forage should you feed before riding? A small amount is already worthwhile – think of a handful up to half a kilo of forage mix while you get ready. The aim is a stomach that is not empty, not a full meal.

Could my horse have gastric ulcers without me noticing? Yes. Gastric ulcers often produce vague signs. Only gastroscopy gives certainty. If in doubt, speak to your vet.

Sources

• Sykes B.W. et al. (2015), ECEIM Consensus Statement – Equine Gastric Ulcer Syndrome in Adult Horses, JVIM: https://onlinelibrary.wiley.com/doi/10.1111/jvim.13578
• Lensing R. et al. (2026), Update on diagnosis, nonpharmacological treatment and prevention of Equine Gastric Ulcer Syndrome, Equine Veterinary Education: https://beva.onlinelibrary.wiley.com/doi/10.1111/eve.70037
• Galinelli N. et al. (2021), J Anim Physiol Anim Nutr: https://onlinelibrary.wiley.com/doi/10.1111/jpn.13215