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Digestive Aids - what is available to racehorses?

By Dr Catherine Dunnett
First Published: 16 July 2009 - Issue Number: 13

Horses in training are susceptible to a number of digestive problems, such as gastric ulcers, colitis and colic. Although less severe, chronic loose droppings, which may be associated with a failure to thrive, are also fairly common.

The prevalence of these conditions amongst racehorses is likely to be a consequence of our feeding and management practices, given the anatomical design of the horse’s gastrointestinal tract.
While the cause of gastric ulcers is fairly clearly defined, the trigger for other digestive issues such as colic or colitis is less easily explained. Likewise, the cause of persistent loose droppings in some horses in training cannot always be found. However, in all of these cases a disruption to the normal microbial balance within the digestive tract may contribute to the underlying issue.

Nearly three billion bacteria in the caecum alone
The microbial community within the equine digestive tract consists of a vast population of bacteria of many different types, as well as other organisms such as protozoa and yeast. We should not think of this population as being static, as it constantly changes in response to the diet and is also influenced by other environmental and management factors. The microbial population is particularly sensitive to any sudden change in diet, especially where the starch and fiber content of the ration is concerned, e.g. as may occur when a horse in full training on full rations is injured and requires box rest with a swift change to a convalescent diet. Veterinary medications including some antibiotics and worming treatments have also been shown to have a detrimental impact on the microbial balance in the gut. A change in environment or travel, as well as racing itself, can also impact on these microbial communities as a result of the response to stress.

Balance on the inside maintains health on the outside
Disruption to the normal balance of bacteria in the hindgut particularly can have a profound impact on both short term and long term health in racehorses because they are dependent on the activity of these bacteria for a number of crucial digestive and other functions including:
• Fermentation of fiber as an energy source
• Fermentation of starch that escapes digestion in the small intestine
• Metabolism and removal of lactic acid produced as a result of this starch fermentation
• Assistance in water re-absorption from the hindgut
• Synthesis of a wide range of B vitamins crucially needed for energy metabolism
• Maintenance of a healthy immune system through the constant stimulation by resident bacteria
The ability of the bacterial population to ‘do their job’ can be compromised to a lesser or greater extent when the nature of the bacterial ...

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