How dental disease can cause weight loss in horses

Dramatic weight loss can often occur when horses 
can no longer properly chew their feed


The clinical symptoms of slowly advancing dental disease in the older horse are not always overtly obvious, can be quite subtle and may even be discounted as ‘just’ a sign of old age.

And so it is that owners and caretakers of an older horse can be taken by surprise when their horse — who was seemingly doing well for years — now begins having troubles maintaining a healthy body condition.

At first, weight loss may occur only in the late winter or early spring, and then when the soft rich grasses of the spring arrive the horse rebounds, blooms and returns to a good state of condition giving the owners relief from concern.

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However, the horse repeats the fluctuating body condition cycle once again the next winter and spring. The cycling of body condition may go on for three or four years, with the horse’s loss of body weight progressively becoming more exaggerated and severe. Eventually the horse owner will seek veterinary attention for dramatic weight loss and dental disease will be identified.

Older horses presented to a veterinarian with a history of unknown weight loss need to receive a complete physical examination and perhaps even laboratory tests to rule out metabolic diseases, neoplasia, degenerative joint diseases, and hepatic, cardiac, pulmonary, and renal disease. Although these conditions can contribute to an older horse’s ill health and weight loss, unidentified dental disease is by far the most common and prevalent clinical finding. The extent of this diagnosis can only be determined once a complete and thorough oral examination has been conducted.

Maintaining a full set of healthy teeth is ideal for the horse throughout its life, yet there are various reasons the dental arcade is no longer an effective and functional chewing unit. When the teeth are unable to properly chew the feedstuffs into a porridge-like consistency, the remainder of the horse’s digestive tract cannot compensate for this insufficiency and thus the horse becomes unable to support its energy demands and maintain body condition.

One of the most notable biological features of the equine tooth is its continual eruption from a reserve crown stored in the dental socket of the jawbone. Ideally an equivalent amount of reserve crown erupts from the dental socket to compensate for the ongoing wear of grinding feedstuffs. A five-year-old adult horse will have permanent teeth which are 4-1/2 to five inches long, with the majority of the tooth remaining below the gum line in the dental socket.

The rest of the tooth will slowly emerge from the jawbone similar to a lipstick or deodorant stick, at a rate of about one-eighth of an inch each year as the horse ages. Since the average permanent molar tooth will have a reserve crown of approximately the length of the tooth, horses can be expected to have fully functional teeth for 25 to 30 years under ideal conditions.

Even though horses do have continually erupting teeth for most of their lifetime, there is a finite amount of tooth that is available. After age 20, eruption amount is significantly small and the tooth begins to lack the structural strength of younger years. Finite tooth amount is a necessary consideration on all age groups of horses, but even more so for horses over 20 years of age.

The interwoven folds and contrasting densities of enamel, dentin, and cementum on the chewing surfaces of the teeth create an irregular and serrated surface effective for grinding fibrous plant material. However, the chewing surfaces of the teeth must contact properly for efficient grinding to occur. The constant eruption of each tooth must be equally matched with wear from its partnering tooth.

If not, the abnormal forces begin to disrupt the physical structures of the teeth. When enamel-to-enamel contact is disrupted, the weaker, softer tooth is soon overwhelmed and misshapen by the dominant tooth. Unfortunately as the physical structure of any one tooth in the horse’s mouth changes, a myriad of problems ensue to accommodate the misshapen tooth or teeth.

Horses with problematic dental occlusion — that is, improper meeting of teeth — accumulate and accrue severe abnormal wear patterns of the teeth and dental challenges over time.

Without recognition and intervention, uneven wear gains momentum and progressively worsens, bringing with it various pathologies. Therefore identifying problematic dental occlusion early on in the life of a horse can avoid or minimize many complications and dental challenges as the horse ages.

Horses with poor or aged dentition often require additional nutritional support as well as proficient dental care in order to maintain their body condition and quality of life. At times it may not be possible to fully resolve long-standing pathology and compensation patterns that have taken years to develop. Dietary changes replacing and compensating for the work of the teeth can make a tremendous difference in the lives of dentally challenged horses, extending the quality and quantities of their years beyond what might be anticipated.

Timely, judicious and prudent dental evaluations throughout a horse’s lifetime are the best strategy for providing the older horse with the best possible dental health.

About the author

Contributor

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

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