Have you ever thought about the mouth being the first part of the digestive system? We often do not think about the impact that oral health has on our digestive health. This becomes especially true when we think about horses! Horses are categorized as having hypsodont teeth meaning that their teeth are constantly erupting over their lifetime until all the tooth below the gumline is used up. This is in contrast to rabbits that are constantly making and erupting new tooth over their life which is classified as elodont. Because of the finite nature of the reserve crown, the part of the tooth under the gumline, it is extremely important to understand how a horse’s mouth is designed to chew and how best to care for their teeth.
So back to our digestive system and how it relates to the mouth. The oral cavity is designed to prehend and sort through feed. Have you ever watched your horse grazing and picking up certain feeds while filtering others out of their mouth? Their lips are absolutely amazing at feeling their way through their feed environment. They use their incisors, the front teeth, to cut grass stems with ease. Once the feed is in their mouth a horse will use their large, powerful tongue to move food back in the mouth to get to the area of the premolars and molars. The mouth of a horse is designed to chew in a circular motion, moving in many different directions which is very different from the up and down motion of a human jaw while chewing. As the feed gets balled up in the mouth and gets moved around by the chewing motion it is moving in a spiral motion from the premolars all the way to the back molars then will be swallowed. All of that chewing takes their feed from large pieces of grass to 2cm or smaller pieces by the time it reaches the back of the mouth.
Horses also are great at producing saliva but they need to be chewing in order to do that. On average a horse can produce up to 5-10 gallons of saliva per day! Why is this important to digestion you may ask. Saliva lubricates the food and helps it break down and be easier to swallow. The most important part of saliva is that it is a buffering agent and helps to buffer the high acid content of the stomach. The more a horse chews the more saliva is produced and in return the better the buffering capabilities and reduced gastric ulcer formation.
Now that we have a good background on what the mouth is doing let’s think about if it isn’t working well and what would happen. If a horse has a painful tooth from a fracture, periodontal disease, or even a mouth that has malocclusions and isn’t balanced properly that can lead to abnormal chewing or less chewing. If the food is not being properly broken down it will reach the back of the mouth at a much larger size than ideal. There will not be as much saliva produced so the stomach acid levels will be higher. Once the food gets to the stomach it sits in the acid vault the same amount of time whether it is the ideal 2cm size or let’s say an increased size of 4cm since it did not get chewed well. That food is broken down some but then leaves the stomach larger than it should to move in to the small intestines. Once in the small intestines the body works to pull out key nutrients. If that food Is not fully broken down due to the large size the nutrients can not be fully extracted. That food then moves in to the cecum and large intestine where it can create more gas and disrupt the delicate bacteria that live there. The large pieces of grass are then passed in the feces where you as the owner can see the large stems as you examine the feces from your horse.
Now we can see how the mouth plays an intricate role in the digestive system. Without the mouth functioning properly the rest of the GI tract can not effectively do the job of digestion. Taking care of your horse’s mouth is not only important to their overall wellbeing but is so important to keep their GI tracts working properly. When mouths do not function well it can lead to increased risk of choke, colic, gastric ulcers, and nutrient loss. The key to a healthy horse starts with a healthy mouth!
Dr. Alicia Bruchman
