In evolutionary terms horses are nomadic trickle feeders; a lifestyle often contrary to the performance horse, which is subjected to prolonged stabling and intermittent feeding.
However, in order for the performance horse to meet the demands of competition this lifestyle is considered necessary.
In the horse, gastric acid secretion is continuous, which not only leaves the stomach lining vulnerable to damage when little food is present but can also lead to bolting of feed, and in turn increased gastric emptying when feed is offered.
When combined with the typical diet of the performance horse, incorporating high volumes of soluble carbohydrate and limited fibrous carbohydrate further complications arise.
This type of diet increases secretion of gastric acid, rate of gastric emptying and reduces the volume of saliva produced to naturally buffer gastric acid.
As a consequence, enzymatic digestion in the stomach and small intestine is limited, with undigested feed ultimately reaching the site of microbial digestion; the cecum and colon.
Micro-organisms in hindgut convert a portion of this type of carbohydrate into lactic acid, which can lead to a condition called Hindgut Acidosis.
From this, detrimental changes to the gut microflora occur, with growth of pathogenic bacteria colonizing compromised areas (such as the pits left by parasites) and eroding the lining of the colon.
Lysis of beneficial bacteria releases damaging endotoxins, which if absorbed can result in colic, diarrheoa and laminitis.
Indeed, in a study by the Japanese Racing Association in 2002 endotoxins were injected into the artery feeding the hindgut and anterior portion of the small intestine, and subsequently induced colic.
Other factors such as stress limit prostaglandin E activity, stimulating gastric acid secretion whilst inhibiting gastrointestinal blood flow and mucus production. Intensive training can also reduce blood flow to the gastrointestinal tract, depress appetite and strip the horse of important amino acids needed for cell regeneration, such as glutamine.
Stereotypies have frequently been associated with ulceration, although whether they are a cause or an effect is an ongoing debate, and prolonged use of NSAIDS and parasitic damage are also strongly implicated.
In summary, for the horse to perform to its maximum potential an energy dense diet, stabling and intensive training are all considered necessary.
Under these circumstances digestive health is paramount, particularly considering that all biological systems rely on efficient nutrient ultilsation to function properly.
A healthy digestive system enables optimal ingestion, digestion and absorption and allows the horse to meet and indeed exceed, the demands placed upon it.