"When horses go more than four hours without food, they’re technically fasting."
Horses are grazing animals. They are designed to constantly be digesting small amounts of forage at all times. How does the GI tract in horses work exactly and what does it mean for their wellbeing?
The horse is a non-ruminant herbivore. Non-ruminant means that horses do not have multi-compartmented stomachs as cattle do. Instead, the horse has a simple stomach that works much like a human’s. Herbivore means that horses live on a diet of plant material. The equine digestive tract is unique in that it digests portions of its feeds enzymatically first in the foregut and ferments in the hindgut.
The horse’s digestive system really should be thought of as being in two sections. The first section has similarities to the digestive system of a mono-gastric animal such as the dog or human. The second section is more like the rumen of a cow.
Starting at the mouth, while eating, the horse produces saliva from 3 pairs of glands. Horses will produce between 20-80 litres of saliva per day. Salvia contains bicarbonate which buffers and protects amino acids in the highly acidic stomach. Saliva also contains small amounts of amylase which assist with carbohydrate digestion.
Next, moving to the stomach. It is small in relation to the size of the animal and makes up only 10% of the capacity of the digestive system or 9-15 litres in volume. In comparison, the human stomach makes up 17% of the digestive system. The natural feeding habit of the horse is to eat small amounts of forage often. Domestication has brought a change to all this. Horses are now expected to eat large amounts of grain feed once or twice a day to suit our lifestyle. This greatly undermines the horse’s digestive capabilities and health. It has been established that we can improve the digestive efficiency of a horse by feeding small meals often. In other words, to assimilate natural grazing.
Once in the stomach, feed is mixed with pepsin (an enzyme to digest proteins) and hydrochloric acid to help break down solid particles. In the lining of the stomach there are specialized cells, called “parietal cells” whose job is to produce stomach acid. The acid is then secreted into the stomach by proton pumps (enzymes). In humans and many other animals, proton pumps are regulated by the nervous system and hormones. In horses, stomach acid is produced, and secreted, constantly. That’s 24 hours a day, 7 days a week.
The hindgut or large intestine is where the majority of a horse's digestion happens. The large intestine is about 62% of the digestive system.
Horses do not have a gall bladder. This means they have no where to store the bile that is produced by the liver. This bile is what helps break down and digest food in the intestines. In humans, dogs, goats and sheep, this bile is released by the gall bladder as needed. This is not the case for horses. So what happens when there is no place to store this bile? It is constantly released into the small intestine, regardless of whether there is food to digest or not. If your horse has gone a prolonged amount of time without eating, they may start to look a bit jaundiced (yellowish in the whites of eyes and gums) from the build-up of bile in the bloodstream.
To sum it all up, Horses should eat constantly because their GI tract is designed to always be digesting small amounts of forage as they graze nearly around the clock. It just makes sense that since that’s the way it works, that’s how we need to feed for them to be most healthy.
Don’t want to be so worried about potential risks to your horse’s health? Make sure your horse has access to quality forages at all times. This could mean letting your horse stay out in pasture, or investing in some high quality slow feeders to make sure your horse has access to small amounts of forage...constantly!