Probiotics, prebiotics and horses

When supplements or products containing live micro-organisms are fed to horses the products are called probiotics, and Latin names like Lactobacillus, Acidophillus, Entercoccus, Bifidobacterium, and Saccaromyces will appear on the product’s ingredients label.

While prebiotics have a similar intention to probiotics they do not contain the actual micro-organisms, rather substances which have been extracted from fermentation vats where selected microbes have been grown. They are indicated to help “feed” the beneficial intestinal microflora. Although the mechanism of action for probiotics and prebiotics is poorly described, it is thought they support or enrich the populations of beneficial microbes in the horse’s hind gut and thus improve digestive health.

The health of horses is highly dependent upon a thriving population of essential microbes in the hind gut that produce enzymes necessary to digest or break down plant fibre. Their presence is absolutely crucial to the horse, as horses themselves lack these vital enzymes.

Byproducts of the fermentation process provide the horse with energy and micronutrients. When in good numbers, these microbes provide as much as 70 per cent of the horse’s energy and synthesize enough B vitamins and vitamin K to meet the horse’s needs. In exchange for this energetic and nutritional advantage billions of bacteria, yeast and protozoa are housed in the warm, moist confines of the horse’s hind gut and are provided with a steady supply of fibrous “plant food.”

It is important to understand that grass and hay are the most important prebiotics for horses as plant fibre is the ideal food source for hind gut microbes. Any departure from a steady influx of an all-forage diet is detrimental to beneficial populations of microbes and thus the health of the horse. The health of these essential microbes is ultimately dependent upon this very specific food source.

Many events in the life of a domestic horse can upset the delicate balance of the hind gut. These include an abrupt change in feed, high-grain diets, processed feeds, weaning, vaccination, deworming, stress from training and travel, changing companions, or a course of antibiotics. Illnesses such as colic, laminitis, inappetence, diarrhea, fatigue, ill-thrift, skin and hoof problems, behavioural and performance changes are often rooted in feeding and management practices which are detrimental to the health of a horse’s hind gut.

Each horse develops a highly individualized microbial population specific to their own diet, their own environment and their own biochemistry. They are virtually “supplemented” with a variety of micro-organisms while ingesting their feedstuff. Simply adding more of the ‘good’ bacteria, even if we knew for sure which ones these were, will be limited by the health of the hind gut first and foremost.

When hind gut health is not optimal the application of probiotics and prebiotics may offer temporary benefit until hind gut health is restored. If a horse is healthy, and has a healthy lifestyle, they will have a healthy hind gut and will inherently be able to support their own population of vibrant microbes.

About the author


Carol Shwetz is a veterinarian focusing on equine practice in Millarville, Alberta.

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