Your horse’s health depends not only on what he eats, but how he eats!

I often think of horses as the whales of the prairie. Whales are the largest of mammals, yet they eat tiny fish and krill in order to stay alive. Horses are among the largest land animals in North America, yet they’re nourished by eating tiny blades of grass – millions of tiny blades of grass, every day.

Horses are designed to eat little and often, and a grass based diet is the cornerstone of a healthy feeding program. In addition to what we feed our horses, it’s important to consider how we feed them too.

How horses eat and chew

As prey animals, horses are gatherers. They use their mouths and jaws primarily for eating, and only occasionally for fighting. They tend to have smaller mouth openings than predatory animals, and have lips that are capable of grasping and moving food into their mouths. Drinking is usually done in a sucking manner, using the lips and tongue.

Horses chew with hypsodental molar teeth (teeth that continually erupt). In fact, these teeth require the stimulation of chewing in order to erupt in a normal fashion. The incisors (front teeth) are large and used for grasping, biting, ripping and keeping food inside the mouth. Horses also have canine teeth, which evolved for fighting, but these can interfere with eating when they become too long.

Before the horse’s incisors grasp and rip foliage, his nose needs to detect food choices. Then the lips must sort the food. If the nose is not working because it isn’t lowered long enough to drain any inflammation, the horse may make improper food choices.

As soon as food is apprehended, the molar teeth begin grinding. In order for this to happen, the tongue must position the food correctly for efficient grinding and appropriate swallowing. Even though the incisors are not directly involved in grinding food, they are still important for efficient chewing. If they are unbalanced or unevenly worn, the food is not ground efficiently and digestion is inhibited. Overbites or underbites can also affect how efficiency a horse can eat.

The significance of head position while eating

Muscles

For the horse, eating happens while he is standing, so that he’s ready to flee if necessary. Eating while standing, with the head lowered to the ground, is a natural process for the horse. Eating with his head raised above shoulder height takes additional effort, and this can fatigue the extensor muscles in his neck.

The weight of the horse’s head and neck (the spine is heavy, too) is an anatomical feature he must overcome when raising his head for long periods of time. Chewing is made possible through the coordination of many muscles and physiologic systems (that also allow for breathing, swallowing and salivary secretions). This requires a great orchestration of neural input, while at the same time cells are accumulating waste products as they work towards lifting the weight of the horse’s head. Without sufficient stretching and movement, the extensor muscles in the neck retain their metabolic waste products for a longer period, and can become sore.

Giraffes eat with their heads extended upward, but they have a mechanism built into their neck muscles that allows for a reduction of waste products from these tissues. A giraffe’s head is also lighter than a horse’s, which allows for better stamina and no fatigue in the neck muscles. The sheer size of the giraffe’s heart and lungs accommodates this adaptation and allows for better pumping of waste materials from the head and neck. The horse, on the other hand, is not equipped in the same way for eating with his head up.

Teeth and chewing

The horse’s teeth are also affected by the position of his head when he eats. When he eats off the ground, he is able to grind all his molars equally because his lower jaw slides forward slightly and the teeth furthest back engage with the teeth above them. When horses eat with their heads raised too high, the jaw doesn’t slide forward and the last tooth does not grind, creating a long, sharp hook that later impedes jaw motion. When the jaw doesn’t move forward, the tempormandibular joint (the hinge joint) becomes painful.

The temporamandibular joint (TMJ) provides important sensory information to the brain related to balance and equilibrium. When this joint is painful, this sensory input becomes altered. A horse with a sore or restricted TMJ may become clumsy, tired and could be more easily injured.

Horses who eat from raised hay nets often require more dental care. We recommend having their teeth checked every three to six months to look for and correct any irregular wear before it changes the sensory input for too long. These horses may also require more food or more frequent changes in feed because they don’t chew their food very efficiently. How the food is chewed determines how it is digested, and influences how the gastrointestinal (GI) tract moves, how acid is released in the stomach, and many other coordinated functions that go along with eating.

Spine

Subluxations in the neck and back of the spine can be caused by arrhythmic chewing. These horses may show hind end lameness, and loss of muscle along the longisimus and

intersegmental regions of the back. These subluxations can be on the same as the dental issue, or on the opposite side depending on how the horse is using his jaw. Often resolving the dental issue will begin to resolve the subluxation associated with it.

Abnormal behaviors exhibited while eating are often caused by poor jaw movement. These might include dropping food, or eating with the head titled to one side. An AVCA certified animal chiropractor can help identify and address issues caused by spinal subluxations and imbalances in the horse’s jaw.

Movement and digestive health

Movement is life. Without movement, the brain and spinal cord don’t receive the information they need from the body in order to determine its relationship to the earth. Lack of movement also creates a hard time for the nervous system, which needs to be nourished by the fluid that surrounds it to stay healthy.

When a horse moves his body, the brain and nervous system send signals to the rest of the body. These signals are important for all sorts of digestive functions, such as making stomach acids to digest food, moving ingested foods through the bowel, and absorbing nutrients from the food along with water. When an animal doesn’t move enough, not only do some of the muscles become weak, but the brain and nervous system also become less attuned to incoming information and communication.


Amy Hayek is a veterinarian and writer for many equine health magazines.  She practices in Meridian, TX with her husband, Dr. Bill Ormston and shares her education and experience with doctors through teaching at the premier online school for Animal Chiropractic, Animal Chiropractic Education Source.  Find an AVCA certified doctor in your area and learn more about how your horse can be healthy at www.animalchiropracticeducation.com and www.allcreatureseveryspine.com the website for her clinic.  Join her on Facebook at @animalchiroaces.

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