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Quick Facts – The Equine Gut

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The Mouth

  • A grazing horse will average 60,000 jaw sweeps per day. With stabled horses this is greatly reduced.
  • A 500kg horse will take an average of 3400 jaw sweeps and 40 minutes to consume 1kg of hay. Ponies can take up to twice as long.
  • Food texture dramatically influences chewing rates.
  • Horses which predominantly graze have fewer sharp edges on their teeth.
  • Feeding large amounts of grain or short feeds changes the chewing action of the teeth and affects the wear on them.

The Stomach

  • The stomach makes up 10% of the capacity of the digestive system.
  • The equine gut is designed to eat small amount of forage regularly. Modern management systems often fail in this leading to gastrointestinal issues including ulcers and colic.
  • Hydrochloric acid and enzymes including pepsin start to break down foodstuffs.
  • Passage of food in the stomach can take as little as 15 minutes.
  • There are 3 areas in the stomach; the saccus caesus, fundic and pyloric regions.
  • Some fermentation naturally occurs in the stomach which is slowed and halted by the hydrochloric acid.
  • If the stomach is empty, the stomach acids destroy the squamous cell in the gut lining causing ulceration.
  • 80% of thoroughbreds have some degree of ulceration.
  • Natives and those susceptible to laminitis, EMS etc often have very limited food intake so care needs to be taken to provide enough food so the horse can still trickle feed.
  • Ulcers affect appetite, condition, performance and behaviour.

Small Intestines

  • The small intestine is 28% of the digestive tract and is 15-22meters long.
  • Its capacity is 55-70 litres.
  • There are 3 sections; the duodenum, the jejunum and the ileum.
  • Digestion is predominantly by the enzymatic breakdown of proteins, starches and sugars secreted by the pancreas, and by emulsification of fats by the secretion of bile by the liver.
  • 30-60% of carbohydrates digested are absorbed in the small intestines, along with fat soluble vitamins and some minerals.
  • Digesta (that’s the food plus the gut ‘juices’ mixed together) takes between 30 minutes and 4 hours to pass through the small intestines.
  • The longer the digesta is in the small intestine the greater the enzymatic action and the more benefit the horse gets from the food.
  • Feeding fats slows food transit through the small intestines.

The Hindgut

  • The hindgut consists of the large intestines, the caecum, the large and small colons, the rectum and the anus.
  • The hindgut is 62% of the gut, it is 7 meters long and capacity is 140-150 litres.
  • Digestion is by microbial action. Billions of microbes including bacteria, viruses, protozoa, and fungi make up the gut microbiome which break down plant fibres and undigested starch into volatile fatty acids which are easily absorbed through the gut wall.
  • Microbial fermentation produces vitamin K, B-complex vitamins and fatty acids which are absorbed through the gut wall and utilized by the horse.
  • The caecum is 1.2 m long and can hold 28-36 litres of fluid feed. Food will remain in the caecum for up to 7 hours.
  • The large colon is 3-3.5meters long with a capacity of 86 litres. Food remains here for 48-65 hours.
  • The small colon is also 3-3.5meters long, with a smaller diameter and absorbs moisture back into the horses’ body, whilst forming faecal balls of indigestible material for expulsion through the anus. This process takes between 36-72 hours.
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