This is a great educational video (courtesy of Dengie Horse Feeds) that explains, in simple terms, the key points of ‘normal’ digestion in horses. Equine digestion is a complicated process and therefore, enhanced understanding and best practice will help get the most out of feeding routines by increasing the absorption of nutrients and reducing the risk of conditions such as, Gastric Ulcers, Colic (blockages) and Equine Exertional Rhabdomyolysis (Tying-up).
Chewing – the mechanical grinding of food (in a side to side motion) makes the food more available for digestion and for the nutrients to be absorbed.
Dental care in horses is essential to maintain this correct grinding of food.
Oesophagus – delivers the food to the stomach
but it’s a one-way journey, as horse’s aren’t able to vomit and so it is particularly important horse’s don’t ingest something that they shouldn’t!
There is a ‘non-glandular or squamous’ region and an acid producing ‘glandular’ region which breaks the food down into: Protein, Fats and Carbohydrate (Starch & Fibre).
Therefore, there is always acid present in the glandular region and research has indicated for some time now that the absence of food in the stomach contributes to the development of Gastric Ulcers (Andrews et al. 1999). However, under normal feeding conditions, horses trickle-feed a minimum of 10 to 12 hours a day which buffers the presence of acid and additionally helps the horse to overcome the problem of having a relatively small stomach (Al Jassim, et al. 2009).
ABSOPTION IN THE GUT
Small intestine (Duodenum, Jejunum and Ileum) – digestive enzymes (released from the pancreas) enter the small intestine and continue the break down of Starch, Protein and Fat which are absorbed via the intestinal wall into the blood. Horses do not have a Gall Bladder to store bile, and therefore bile produced in the liver is continuously secreted into the small intestine to emulsify and break down fats.
Research suggests that large meal feeding and/ starch intake, increases the quantity of starch that escapes digestion in the small intestine which then passes to the hind gut (Richards, et al. 2006).
Large intestine (Caecum, Large Colon and Small Colon) – Fibre is broken down by microbes via hind gut fermentation into volatile fatty acids (VFAs), mainly acetic, propionic, and butyric acids and which are absorbed via the intestinal wall into the blood. Furthermore, water and electrolytes are reabsorbed to keep the horse hydrated.
Any Starch not digested in the small intestine results in hindgut starch fermentation and subsequent acidosis, causing digestive disturbances that may reduce a horse’s ability to perform athletically and contribute towards incidences of disorders such as colic (Richards, et al. 2006).
Image: Courtesy of www.horsehage.co.uk
Key points on digestion
Horses have relatively small stomachs therefore, they are often defined as ‘trickle-feeders’. The glandular region of the horse’s stomach produces acid continuously and research indicates the absence of food contributes to Gastric Ulcers. Therefore, it is now widely accepted that best practice is to ensure horses are fed a little and often, rather than large meal-feeds, which promotes the absorption of nutrients and also minimises the risk of blockages (Colic).
High fibre diets may be the most natural for horses but horses are also efficient at digesting fats therefore, it is a useful way to provide high energy diets for performance horses, rather than high cereal feeds resulting in hind gut fermentation of starch and acidosis which in turn, may lead to digestive imbalances and reduced performance.