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Digestive Problems Explained

By Dr Tom Shurlock, Consultant Nutritionist at British Horse Feeds

The horse is a grazing herbivore and has evolved over the ages to obtain its nutrition from the digestion of grass. He is a trickle eater and to function at his best it needs to keep its gastrointestinal tract (GIT) full. This is because the whole tract is held in place by a very thin layer of connective tissue and is only anchored at the mouth and anus. If it is not kept full and taut, problems can occur and in the main one of two: colic and ulcers.

Many digestive problems in the horse revolve around colic. Colic is not a single condition but a symptom of GIT malfunction. It encompasses compaction (gullet and stomach), ulcers along the whole length of GIT, twisting of the gut itself, build-up of gases, ingestion of foreign bodies (e.g. sand/earth) and endotoxins caused by microbial population breakdown.

Additionally, the stomach can also be prone to upset, mainly in the form of ulcers. The horse’s stomach constantly secretes hydrochloric acid. For a trickle eater this is essential as the acid helps prepare food for enzymatic digestion – and microbial fermentation – in the intestines. To protect the stomach lining there are also specialised secretory cells (goblet cells) that produce a mucin coating the lining in the lower half of the stomach. However, if a horse is fed individual meals, is stressed – and stabling, transport, training and unfamiliar surroundings can all be stress factors – or exercised on an empty stomach (the acid sloshes up into the unprotected portion), there is disruption in normal gastric functioning. Excess acid is not bound within the food and mucin secretion can stop. Stomach linings can be exposed and the acid can act directly on it causing acid burns, lesions and finally ulceration. Also, if feeding starchy diets, the acidity is compounded by a shift in microbial population that further drives down the pH, favouring necrotic bacteria that can penetrate the mucus lining and infect the stomach wall.
To avoid the triggers we need to feed for the GIT as well as the horse. Gut-fill is important, but it must be mainly fibre or forage. The physical presence of fibre generates saliva through chewing, soaks up excess stomach acid and allows the gut contents to be pushed along its length through muscular contraction (peristalsis). This avoids twisting (torsion), build-up of gas and pushes foreign bodies into the rectum and away. As it is a constant delivery system, dietary stresses are minimized and gut physiology optimized.

The presence of fibre ensures a good hindgut population of microbes that maintain the correct environment; overfeeding of starch and protein can upset this balance (as the small intestine cannot cope with excess nutrients) as they will alter the balance in the hindgut resulting in microbial death and endotoxins.

Additionally, there are components within fibre that have other effects. Pectins – soluble fibre held within the structural matrix - can bind to and reinforce the mucosal layer that protects the gut from acid attack in the stomach and microbial attack along the GIT.

However, it is not always possible to provide forage continuously, for a number of reasons; as stated above there are stress factors which disrupt feeding and it may be that there is insufficient energy in a forage diet for a number of activities.

This is where super fibres have a role. With a significantly higher fermentation rate in the hindgut than hay or grass, they can supply additional energy as well as the favourable aspects of fibre. In fact, in addition to their high energy values, both Speedi-Beet and Fibre-Beet have significant levels of soluble fibres that can support the horse’s mucus lining, as well as having high acid binding capacity. This means these products can help mop up excess acid and so have a role in optimizing both stomach and general gut function.

It is these properties that have allowed both Speedi-Beet and Fibre-Beet to be awarded the Gastric Ulcer Feed Assurance Mark by the British Equestrian Trade Association making the both suitable for horses and ponies prone to equine gastric ulcer syndrome (EGUS) as part of a balanced diet.