Equine Digestive Process
Vet, Horse First Aid

From: Horse Anatomy | Care

See also: Tack | Clipping | Rugs | Worming


The Equine Digestive Process
This is the process that allows the nutrients in food  once eaten,  to be broken down  and used within the horses body.  

What  Feeds Are Broken Down Into
 Once broken down nutrients obtained from the feeds such as carbohydrate, fibre, protein, vitamins, minerals, water  and fats are able to be used by the horse.  

The  Equine Digestive System
From the moment food enters the horses mouth it begins the digestive cycle, with each part of the horses body having a role to play.

The horse first of all smells the food that is in front of them, by doing this they learn what they are about to eat. It is because of this sense of smell that some horses will refuse to eat medicines that are put into feeds no matter how hard you try to disguise it.

The  horse uses its whiskers to feel and sense what is in front of them and this combined with an excellent sense of smell helps the horse to know what they are about to eat.

The horse has  soft mobile lips which they use to move and also  pick up the food  that they want to eat and leave what they do not  want to eat.

These are the teeth at the very front of the mouth and the  horse uses these to bite into the food  in order to assess what it is about to eat, if it is alright to eat the tongue will then pass the food to the molars who grind it down. There are 12 incisors in total, 6 on the bottom and 6 on the top row.

The tongue is used  to pass food from the incisors at the front to the molar teeth at the back where it mixes saliva with the feed to start breaking down the food.  When the  food has been suitably ground down the tongue will form the food into a bolus,  mixing the food with more saliva  so that it will easily pass through the oesophagus.

This is used to help to soften the food and begin to break down the food starting off the digestive processes. Saliva contains enzymes and bicarbonate of soda, the bicarbonate of soda acts to neutralize the acids in the stomach helping to prevent stomach ulcers and the enzymes also start to break down individual components of food.

There are 24 molar teeth in total with 3 pre molars and 3 molars on each side of  the upper and lower jaw. These molars are used to grind the food down and mix it with saliva to enable smooth passage down the oesophagus.

The pharynx is at the back of the mouth and when the food has been sufficiently ground down it  enters the pharynx where  it passes quickly into the oesophagus, this is because the soft palate acts to prevent food from entering the trachea ( wind pipe) by covering it over when the horse swallows. An interesting  fact to remember is that horses cannot breath through their mouths  only through their nostrils

Once food enters the gullet a series of muscular movements combined with released fluids moves the bolus of  food down towards the stomach. There is a muscle at the base of the oesophagus and that enters the stomach called the cardiac sphincter muscle, it is a very strong muscle that prevents the horse from vomiting.

The stomach is approximately the size of a rugby ball and  works at its best when it is 2/3rds full. The stomach  secretes hydrochloric acid as well as  mucus to line and protect the stomach  and digestive enzymes such as pepsin  which start to break down the food. The horses stomach continuously produces acid regardless of how full or empty it is. It is when the stomach is empty that the horse can be prone to getting Gastric ulcers and why horses should always be fed little and often. The stomach is made up with different regions that are called  the  Oesophageal region, Cardiac region, Fundic region and Pyloric region. There is a muscle called the Pyloric sphincter muscle which controls the flow of food out of the stomach into the small intestine.

Small Intestine
The small intestine is approximately 50 to 70 feet long and can hold around 12 gallons. The small intestine is made up of three sections called the Duodenum, Jejunum and Ileum. It is in the small intestine that most of the cereal based feeds such as Oats and Barley will be digested  by the body and broken down into fats, proteins and soluble carbohydrates and vitamins and absorbed into the bloodstream. It is in the small intestine that Bile from the Liver  flows and aids in the breakdown of  fats along with  Pancreatic and small intestine  enzymes that also aid in the digestive processes.  The small intestine passes insoluble carbohydrate along to the large intestine for digestion in the hind gut.

Large Intestine
The large intestine is approximately 30 to 40 feet long and is split up into the Cecum, Large and Small Colon, Rectum and Anus.

This is around 4 feet long and can hold approximately 8 gallons. Also known as the hind gut it is here in the Cecum that bacteria work to ferment the fibre and  cellulose in the diet and  to produce fat soluble vitamins and volatile fatty acids.  The bacteria in the Cecum  are sensitive to change  and if the horses diet is not changed slowly enough then the bacteria cannot  cope and this  leads to   the horse having colic.

Large Colon
This is approximately 12 to 15 feet long and can hold around 20 gallons, it is in the large colon that carbohydrates are absorbed into the bloodstream.  The Cecum folds back and forth over itself and this is another area that can be prone to giving the horse colic in the Cecum it occurs when food matter gets itself stuck.

Small Colon
This is approximately  12 to 15 feet long but unlike the Large Colon only holds around 5 gallons. It is here in the small colon that water and electrolytes are  absorbed  and the remaining waste matter  starts to form into small balls ready for the rectum.

Rectum and Anus
The rectum is approximately 1 foot long and it is here that the small balls of  waste matter collect and wait ready to be expelled through the opening of the Anus.


Digestive Disorders