Horses are single stomach (monogastric) herbivores that evolved to graze on fiber-rich roughage. Their unique digestive system consists of a foregut and hindgut, each with different functions for breaking down feed and absorbing nutrients. [1]

The stomach and small intestines, which make up the foregut, are responsible for digesting proteins, fats, and non-fibrous carbohydrates in the horse’s diet. This happens through mechanical action and chemical reactions facilitated by enzymes.

The hindgut, consisting of the cecum and colon, is where the digestion of fibrous carbohydrates takes place. Bacteria help synthesize nutrients and convert this fibre into usable energy through fermentation. [1][2][3][4]

The process of hindgut fermentation allows the horse to extract nutrients from plant material which are not digestible in the small intestine. [1][2]

Because of their specialized digestive system, fibrous forages should comprise the largest percentage of your horse’s diet. Feeding horses too much sugar and starch from grain-based feeds can disrupt digestive processes in the hindgut and cause gut problems. [1][2][3]

You can support your horse’s hindgut function by feeding a forage-based diet to maintain a healthy gut microbiome. [1] Other factors that affect bacterial populations in the hindgut include the weather, stress, and the use of medications and dewormers. [5][6][7]

How Does the Horse's Hindgut Work

What is Hindgut Fermentation in Horses?

Hindgut fermentation is a unique digestive process that occurs in horses and some other herbivorous animals.

The main purpose of the hindgut is to ferment the complex and structural carbohydrates found in the horse’s diet. [4] Structural carbohydrates include fiber components in the plant cell wall, such as cellulose and hemicellulose. Complex but fermentable carbohydrates include pectin, beta-glucan, plant sugars and fructans, largely found within the plant cell.

In horses, fiber and complex carbohydrates from fresh grass and hay are digested via fermentation by microbes residing in the hindgut. Feeding a diet rich in structural and complex carbohydrates helps to promote optimal digestion and the transit of feed through the equine gastrointestinal tract (GIT). [1]

Hindgut fermentation produces volatile fatty acids (VFAs) that serve as a significant energy source for horses. [4] Most of a horse’s energy requirements should be met through fiber fermentation in the hindgut.

Microbial fermentation also produces B-vitamins and amino acids. These B-vitamins can be absorbed and meet the horse’s requirements. Methane, carbon dioxide, and water are also produced by fermentation in the hindgut. [1]

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