The sheer size and volume of the horse’s gastrointestinal tract is amazing with over 30 metres long of twists and turns. It is therefore vital to understand how it works and how important regular feeding is to keep it running like a well-oiled machine.
At first glance the equine digestive system looks like a mistake. The stomach for example is surprisingly small (7.5 t 15 litre) for a 500 kg animal.
In contrast the small intestine reaches an amazing 22 metres in length. But Mother Nature is smart. The horse was never expected to eat large quantities of food in one sitting it is designed for a wandering lifestyle and eating small food constantly.
The horse grinds it food down with powerful molar teeth mixed with saliva which immediately launches the digestive process. The stomach does not break down food so it’s the teeth’s job to do this. Dentistry maintenance is incredibly important therefore to kick off the whole process. From there it’s over the soft palate down the flexible oesophagus to the stomach where massive muscular contractions move it in only ONE direction. Meaning what goes down HAS to stay down. Horses have NO capacity for vomiting.
The food stays here only for 15 min before heading to small intestine. There’s no time for major food breakdown only for it to be liquefied. Although it’s only a short time the foods presence has a direct bearing on your horse’s health. The stomach lining is extremely sensitive to stomach acid and will easily ulcer if left empty. Food being present in the stomach absorbs this acid. Horses that are fed infrequently, one or two meals a day, rather than several small ones are at risk of stomach ulcers.
The next stop on the tour is the small intestine, the first section has a u shape presumably to stop it returning to the stomach should it become distended. It can hold 30% of the GI tract capacity. It digest proteins , starches/sugars, amino acids and fats which then are absorbed into the blood and off to the liver (the major chemical processing lab). On average it takes 60 – 90 min to pass thru to the next stage the large intestine.
This is where the bulk of the hard work is done. Digestion is via microbes (billions of bacteria) rather than enzymes. They break down plant fibres to volatile fatty acids. Any change in feed/stress can upset and kill off the bacteria and may lead to colic and other gastrointestinal problems.
The large intestine includes the caecum (1.3m approx.), large colon, small colon and rectum.
The caecum is the fermentation vat and the first stage of digestion! It breaks down the plant fibres in 4 to 5 hrs. From here food moves to the large colon 4m in length (can hold up to 60 litres in food!) and is where the food dwells the longest (36 to 48 hrs). Once processed the food moves into the small colon (also about 4m) and the process is nearly complete. Most of the food by now is absorbed so the main function is to reclaim any excess moisture until eventually it’s dried out enough into faecal balls and eliminated. The perfect manure should gently just break apart as it hits the ground. Neither too hard (dehydrated) or too soft (diarrhoea).
The take home message is to feed your horses small meals and often or have access to ad lib hay or pasture. Have good access to water and keep their teeth in top shape to start the digestion process well from the very beginning.