Us humans are funny creatures.

We often have the urge to ‘humanise’ things. However, when we treat horse digestion systems like our own, we can be creating a world of gut health problems for our horses.

Ulcers in horses are widely understood to be a 'man made' problem.  Mostly this stems from a poor understanding of horse digestion.

To better understand equine digestion - here are some interesting ways that a horse's digestive system differs from a human one.

Horse digestion vs human digestion:

Meals or grazing

  • Humans are conditioned to have set meals throughout the day.
  • Horses: Are designed to eat, chew and digest constantly through the day and night.

Stomach acid production

  • In humans: The presence of food in the stomach will stimulate stomach acid production. 
  • In horses, the stomach produces gastric acid 24/7 – regardless of whether there is food in their stomach or not.

Breaking down food

  • Humans have a complex system of mechanical and chemical breakdown to help digest food.
  • Meanwhile,  horses rely primarily on bacterial breakdown to break their food into digestible molecules. When horses have an empty stomach, these bacteria die – which adversely affects the digestion of their next ‘meal’. 

Relative stomach sizes

  • Human stomachs are large & can expand up to 4 times their usual size. This is why our system copes so well with ‘meals’ throughout the day.
  • Horse stomachs, by comparison are relatively small. They are designed to digest small amounts of food on a nearly constant basis. 


  • With humans, vomiting is a defensive action to remove ingested toxic substances from the body.
  • Horses have a muscle that stops them from vomiting. We still don't really understand why horses have evolved not to vomit. However, a popular theory is that their system is built to graze (and take in small portions at a time) and their natural tendency to be fussy eaters that they have never needed to vomit.

Saliva production

  • Salivary production is not constant in horses, as it is in humans. Saliva is alkaline, and it's a great buffer against stomach acid. If a horse doesn't receive enough roughage, they wont produce enough saliva to keep their stomach acids in check. Without that buffer, ulcers can develop.

Managing feeding to best suit horse digestion

First and foremost, a horse must have access to fibrous forage at all times (pasture, hay, silage or haylage). The bulk of our horse's feed should not be grain based ‘meals’. Instead, horses should be able to ingest fodder slowly throughout the day.

Without a constant trickle of food, your horse will produce excess stomach acid. This oversupply of acid is one of the main causes of ulcers in horses.

Feeding roughage

Horses have evolved for thousands of years on low quality pasture and forage - not the high quality grains, hays and pastures we see today.

This means that you should provide constant access to roughage - i.e. hay. In addition, the roughage offered should be a low sugar, low protein variety.

 Types of roughage for horses

Hay: Hay is a harvested plant that has been dried and cured. These are usually legume or grass based plants.

Haylage: Haylage is cut like hay, but only allowed to semi-wilt and not dry completely. The bales are then compressed and wrapped in plastic. This eliminates oxygen reaching it and creates the anaerobic conditions needed for desirable fermentation of the haylage to occur.

Silage: Silage and haylage are very similar. They are both fermented roughages, but the difference between them is moisture content. In general, haylage has a moisture content of between 15 percent to a maximum of 40 percent (60 to 85 percent DM). Silage has a moisture content of more than 40 percent.

HINT: You can combine high quality hay, haylage or silage combined with straw to increase the volume of forage available (and ease the burden on your back pocket).


Feeding small meals and providing access to hay constantly will assist horse digestion. Feeding small meals and providing access to hay constantly will assist horse digestion.


Feeding grain & sweet feeds

To best mimic their natural environment, horses should be fed a diet low in soluble carbohydrates. In general, sweet feed, corn, oats and barely top the list as the grains highest in soluble carbohydrates, whereas wheat bran, beet pulp, alfalfa and rice bran contain much lower percentages.

If you feed grain or ‘hard feed’, it’s best to feed little and often. For example if you currently feed 6 kilos of hard feed, split over two meals - the horse would greatly benefit if this could be split into 1.5kilos spread 4 times through the day.

The importance of probiotics

To digest their food, horses rely on bacterial breakdown. Factors such a stress, a high grain diet or intense exercise can damage of destroy microbes in the hindgut.

The hindgut of the horse has a microbial population including bacteria, yeast, fungi that ferment and breakdown fibre.  Without these microbes in the hindgut, horses would not be able to digest and utilize plant material such as hay and pasture.

To efficiently digest fibre, the microbial population of the hindgut must be healthy and their numbers maintained at appropriate levels. This can be with the addition of a fermented food like haylage or silage - or a probiotic supplement