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Some feeds can be too easy to digest for horses

The mechanics of nibbling, chomping and crunching are important to horse health

There is a harmonic resonance that is audibly evident when a horse chews.

This chewing sound soothes, calms and contents the nervous system of the horse, and most horse owners would agree that it also soothes the nervous system of the human.

There are many reasons chewing is an important part of a horse’s life beyond that it simply sounds good. Chewing is a major part of what a horse does, and when its lifestyle and environment do not accommodate this biological need it becomes problematic for many aspects of its health.

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The time spent chewing is essential to the health and happiness of the horse.

Horses have evolved in an environment where they need large volumes of forage to meet their energy and nutrient needs. So they graze, forage and browse more or less continuously throughout the day, upwards of 16 to 18 hours, often on the move to do so. All the while the horse is nipping with its incisors, chewing with its molars and swallowing.

Processing large volumes of fibre translates into a lot of time spent chewing. Horses engaged in foraging behaviour will chew somewhere between 40,000 and 60,000 times over the course of a day. The horse’s digestive tract with its complex microbiome as well as its dental health relies on a near-constant and steady flow of plant matter to remain fully functional.

Unlike the dog or human who tend to be meal feeders, scheduled meals are problematic for the horses that are designed by nature to be trickle feeders. Gaps in forage flow disrupt natural digestive rhythms, unsettle the horse mentally and physically and create digestive disturbances and painful discomfort in the belly.

Digestion begins with the first nip of the incisors. Chewing, grinding and mixing the feedstuffs with saliva is a crucial first stage of digestion. This stage prepares the feedstuffs for the horse’s digestive tract.

The nature and type of the feed a horse eats greatly influences the amount of time it spends on chewing. For example, studies have shown that horses eating one kg of hay or fibre chew roughly 4,000 times while horses given one kilogram of concentrates will average around 1,000 chews and take one-quarter of the time to chew and consume.

A reduction in chewing time is significant to the rest of the digestive tract because the horse is only stimulated to produce saliva when it chews and so the more time the horse chews the greater the saliva output. Saliva acts as a lubricant for ingesta flow and has enzymatic properties which initiate the digestive processes.

In addition, saliva also protects and buffers the lining of the stomach against acidity. The stomach of the equine species is unique in that it continuously produces hydrochloric acid in preparation for the steady flow of forages which would naturally occur in its environment. Whenever gaps occur in the flow of feeds the gastric acids accumulate in the empty stomach and cause painful ulcers to the lining and leave the remainder of the digestive tract vulnerable to the harmful effects of ‘unchecked’ gastric acids.

The motion of the jaw while the horse is chewing is strongly influenced by the nature of its diet. Research has shown that chewing of long-stem plant fibre requires longer, slower jaw movements with a fuller elliptical or circular expression.

This grinding motion is distinctly different from the ‘up and down’ type of chewing evoked from consuming grains and processed feeds. Whenever horses consume the softer modern-day equine diets they lack full and healthy elliptical jaw excursions and quantity of chewing time — both of which are necessary to self-maintain and offset the erupting wear of the teeth.

These ‘unchecked’ overgrowths on the teeth develop into sharp enamel points. The discomfort of the overgrowths and altered jaw motion contribute to the development of pathological hooks, ramps and ridges along the tooth surfaces. These pathologies result in interruptions to the flow of the food bolus as it moves backward in the mouth to be swallowed and interfere with proper housekeeping functions of the oral cavity.

This allows pockets of food to collect and ferment along the gum line. Dental work becomes necessary to address the overgrown sharp enamel points, discomfort in the mouth, poor dental occlusion and abnormal patterns of tooth wear. Sufficient time spent chewing long-stem forages at the ground level is of crucial value to the proper development and maintenance of healthy dentition in horses of all ages.

Whenever a horse is not allowed to engage in sufficient foraging behaviour, it will find alternative ways to meet its basic biological need to chew.

Initially its distress may be visible as an anxious, unsettled or nervous type of behaviour while being handled on the ground or while being ridden. The horse may begin chewing on fences, gates, mangers, trees, buildings, metal and even manure droppings. As its distress escalates, it may develop stable vices such as cribbing, weaving, or stall walking in an attempt to soothe itself.

Chewing forage is an essential part of a horse’s life with significant contributions to both the horse’s health and the horse’s overall welfare.

About the author

Contributor

Carol Shwetz is a veterinarian focusing on equine practice in Millarville, Alberta.

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