How can you keep his hindgut healthy while keeping his waistline in check too? It begins with understanding the parts and purpose of the equine digestive tract, says Dr Laura Wilson.
Horses have a unique digestive system. They are hind gut fermenters, meaning their digestive system is very different from ours, a dog’s or even a cow’s. Rabbits, elephants, and rhinoceros are some of the other animals that have this type of digestive system, but there are few of them.
Your horse’s mouth is an important, and sometimes overlooked, part of his digestive system. It is here that mechanical digestion begins via chewing, and saliva is secreted.
Dental health is vital to overall digestive health, and it is therefore important to have your horse’s teeth checked regularly. Food is broken down into smaller pieces in the mouth to improve its digestibility and absorption of vital nutrients.
If you have an older horse that struggles with their fibre intake due to missing teeth or other age-related dental issues, your feed provider or veterinary surgeon may be able to make recommendations for a forage replacement diet.
This ensures your faithful friend is still getting the vital fibre required for a happy digestive system, but in a format that doesn’t rely quite so much upon chewing.
Forage such as hay, haylage or even grass requires more chewing than concentrate feeds. Increased time spent chewing is beneficial for the horse as it promotes healthy wearing of the teeth and leads to increased saliva production.
Did you know that adult horses may secrete up to 35-40 litres of saliva per day? Saliva plays a very important role in lubricating the food ingested and buffering stomach acid.
Once the food has been swallowed, it passes down the oesophagus into the stomach.
The horse’s stomach can be divided into two parts:
- The lower part of the stomach has a glandular lining, and it is here that the acid is produced in response to a complex pathway of stimulatory and inhibitory signals.
- The upper part of the stomach has a squamous lining. It is this part of the stomach that is sensitive to contact with the acid from the lower part which can, in some cases, lead to gastric ulceration.
Regular forage intake is key to maintain gastric health. The saliva produced during chewing helps to buffer the acid, and the fibre content floats on top of the acidic fluid in the stomach, forming a mat.
This fibre mat acts like a cover and protects the sensitive upper part of the stomach from acid splashing.
Upon exiting the stomach, the food enters the small intestine. This is around 25 metres long in a 500kg adult horse.
Here, some of the protein, fat and non-structural carbohydrates will be digested and absorbed.
The small intestine is also an important site of mineral absorption, with horses absorbing most, although not all, of their daily requirements prior to the food entering the large intestine.
Otherwise known as the horse’s hindgut, the large intestine is what makes the digestive system unique. As hindgut fermenters, horses rely upon a ‘factory’ of micro-organisms that live within the large intestine to be able to release the energy from a forage-based diet.
A regular supply of fibre into the micro-organism factory is key to keeping it healthy and functioning well. Regular fibre intake maintains the complex balance in the large intestine, reducing fluctuations in pH and preserving the microbes at optimum levels.
The amount and type of food ingested has a large impact on the amount of water held in the large intestine and the absorption of water and electrolytes.
This is important for maintaining gut motility and keeping your horse hydrated (two key factors for general health and the prevention of colic).
While most mineral absorption occurs in the small intestine, research in more recent years has shown that minerals are also absorbed in the large intestine.
About the expert: Dr Laura Wilson BVM&S MRCVS is a qualified vet and Technical Advisor at Dodson & Horrell. She graduated from Edinburgh University in 2013 and began her veterinary career in Newmarket, before spending time in New Zealand working with racehorses and Thoroughbreds.