The Equine Digestive System

Bishop Burton College Equine Science lecturer Georgina Smith talks to us about the Equine Digestive System to help us better understand how we feed our horses.

Baillie Haylage have partnered up with the Equine Nutrition experts at Bishop Burton College to provide horse owners with quality feeding advice. Georgina Smith BSc (Hons) MRes explains how important it is to understand the Equine Digestive System and how grass forage can maximise welfare and performance.


Horses have evolved over millions of years to become specialised in their digestive ability. As their habitat changed from trees and bushes to expanses of flat grassland, their feet evolved to gallop and their teeth evolved to graze and grind. Horses will graze for around 16-20 hours a day, meaning their digestive system has adapted to functioning optimally when the horse is trickle feeding (eating little and often). As they have evolved to eat grasses, the gut has evolved to digest these efficiently and maximise energy gained from them. In horses this is primarily in the hindgut as the grass will pass through the gastrointestinal tract with nutrients such as proteins, sugars and fats being broken down and absorbed in the small intestine, leaving the bulk of the grass (the fibre portion) to be fermented in the hindgut for use as the horse’s primary energy source. This system is so specialised, we need to make sure we continue feeding our horses sufficient fibre at consistent points during the day to enable the digestive system to function at its best and avoid any nutritional disorders.

The Digestive Process Starts In The Mouth

The digestive health benefits of a high fibre diet begin with the mouth. Horses are hypsodont, meaning that their teeth grow continuously throughout their life, which is why routine appointments with an equine dentist are so important. We can encourage tooth health by allowing the horse to evenly grind its teeth down naturally by feeding plenty of fibrous forages such as grass and haylage. These tougher materials maximise the horses jaw range of motion and encourage an even wearing of the teeth to help avoid issues such as hooks on the teeth. In addition to tooth health, a continuous supply of forage will encourage saliva production to keep the food lubricated and provide a small buffering action in the stomach which can help reduce the likelihood of gastric ulcers and general stomach discomfort.

Trickle Feeding

Trickle feeding encourages movement through the gastrointestinal tract called ‘peristalsis’ which is highly important to keep continuous flow for hindgut fermenters. Issues with this movement are associated with conditions such as impaction or tympanic colic. Although in mild cases, the horse may be uncomfortable for a while before resolving itself, colic often needs immediate veterinary attention and can require surgery, so it is of the utmost importance that owners provide an adequate supply of forage to keep peristaltic motion. It is recommended that at least 1.5% of the horse’s bodyweight is fed in forage per day (in addition to any hard feeds).

The Equine Hindgut

Finally, as described earlier, the equine hindgut is highly specialised for the fermentation of fibre and this is largely down to the populations of microbes that inhabit the hindgut. These populations should be diverse and fibre-focused which can be achieved by a high forage diet. The golden rules for encouraging a healthy hindgut include

  • making any changes to the diet very slowly (so as not to upset the delicate balance of microbes)
  • avoiding feeds that are very high in starches and sugars (recommended to be no more than 1g per kg of horse’s bodyweight per meal). Too much starch can cause feed to be ‘dumped’ in the hindgut where the microbes will rapidly ferment this and produce excess acid which can disrupt the environment.

Overall, the equine digestive system has taken millions of years to adapt to a 100% forage diet. It could take millions of years for the horse’s system to evolve further to cope with domestic diets! By maximising forage in their diet, providing fibre as constantly as possible and limiting starch proportions, you can optimise your horse’s digestive health and maximise welfare and performance.

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