Ulcers in Horses: Problems of Domestication

Editor's Note: This is an excerpt from Chapter 2 in Care and Management of Horses, written by respected equine author Heather Smith-Thomas. It is currently available for purchase at ExclusivelyEquine.com.

Domestication has created problems for the horse, including stomach ulcers. Stress of confinement and unnatural conditions, stress from emotional and physical aspects of athletic careers--all the stresses that go with trying to adapt to human management--can create ulcers in horses. Ulcers, once thought to be mainly a problem in confined foals, also plague adult horses. Racehorses and other performance horses have an especially high incidence.

Research reported at the 1998 American Association of Equine Practitioners (AAEP) convention in Maryland showed that gastric ulcers affect up to 90 percent of performance horses and that many of the factors associated with intensive training and conditioning contribute to ulcer formation.

Stomach ulcers occur when the lining is damaged by excessive acid or by impairment of the stomach lining's natural protection. Signs of ulcers are dullness, decreased performance, poor appetite, poor condition, rough hair coat, and poor weight gain. Often the problem is not obvious; the horse just isn't doing as well as he should be. Some horses adjust to the stress better than others, but it's hard to predict which ones will have problems.

Many common management practices used with performance horses contribute to ulcer development--high grain/low roughage diets (increased stomach acid due to infrequent high-concentrate meals, with lack of roughage in the tract to help buffer the acid); lack of continual grazing; stress of confinement combined with periods of intense exercise; use of anabolic steroids; the steroid-like plant substances in some feeds; and use of non-steroidal anti-inflammatory drugs.

Ulcers are a major problem, but how much they adversely affect performance has not been determined. Researchers are still trying to find the best methods of prevention, looking at dietary, training, and medical remedies.

Horses are also more susceptible to respiratory problems and other illnesses at times of stress, such as at weaning or after a long trailer trip. The immune system usually protects the horse from common diseases and infections, but stress can hinder the immune system and lower the horse's resistance to pathological invaders. Stress is defined as anything that poses a threat to physical or emotional well-being, temporarily or over an extended period.

During temporary stress, like acute anxiety or fear, the horse's heart rate and blood pressure rise. Circulation to the gut, skin, and other non-athletic parts of the body decreases so blood can concentrate in the muscles and lungs for the exertion needed for fleeing or fighting. After the temporary stress is over, everything returns to normal.

During more prolonged stress, the body secretes hormones called glucocorticoids. One of these, cortisol, is beneficial to the horse over the short term, because it changes the body's metabolism to help it function better under stress. Cortisol creates temporary increase in blood glucose (used as energy) and increase in fatty acids and glycerol.

Glucocorticoids break down reserves of fat, carbohydrates, and protein to release nutrients into the bloodstream. Metabolism switches from a constructive (body building) state to one of using up reserves. Growth, reproduction, and immunity are temporarily suppressed as the body prepares itself for emergency survival (fight or flight--traveling on the "reserve tank" until things get back to normal again--a coping mechanism to escape danger).

Horses under stress are also helped temporarily by increased retention of sodium and water, and increased mobilization of calcium. Probably the most beneficial reaction caused by cortisol is reduction in tissue inflammation, which provides temporary help and relief to the body during trauma and infection. Cortisol blocks the production of harmful substances and toxins, enabling the body to function more normally. All of these changes are beneficial for a day or two, but if stressful conditions prevail, the continuing production of cortisol becomes detrimental because it interferes with the immune system.

As part of the body's defense against pathogenic invaders, the immune system produces antibodies and uses white blood cells to attack germs. These processes and many other biochemical aspects of immunity are hindered when the body is creating cortisol (which is similar to other steroids in its actions). One study showed that responsiveness of white blood cells to invading bacteria was noticeably lower in fatigued horses after strenuous exercise. Overtraining can become a form of stress that leaves a horse vulnerable to illness. Several studies have indicated that the stress of long van trips reduces disease resistance; increased cortisol levels in the body can be measured after a long trip.

The lungs are especially vulnerable to lowered resistance due to stress. Harmful organisms are a natural part of the environment and always present in the air, so the immune system must be strong to protect the respiratory system. Horses tend to develop influenza, colds, rhinopneumonitis, respiratory forms of viral arteritis, as well as other respiratory problems when shipped to shows, races, or sales. Stress -- and contact with other horses -- gives infections a prime opportunity.

Stress may be responsible for more health problems than we realize. Traumatic experience at weaning and subjecting a foal to new things during this time of stress can make a difference in how well he does during winter. Weanlings and yearlings enduring cold, wet conditions (especially if they are also mentally stressed by unnatural conditions such as confinement in small paddocks) seem susceptible to many illnesses. Severe outbreaks of strangles and other respiratory ailments are frequent in young horses after a wet period or weaning. Salmonellosis outbreaks, ulcers, and colic are also precipitated by stress.

Various things stress various horses. Young horses experience stress in situations they are not accustomed to but learn to deal with the novelties (and become less insecure or fearful) as their training level progresses and they accept certain things as non-confrontational and part of their regular routine. Doing familiar things in a familiar environment causes less stress than being subjected to something unfamiliar.

About the Author

Heather Smith Thomas

Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey's Guide to Raising Horses and Storey's Guide to Training Horses. Besides having her own blog, www.heathersmiththomas.blogspot.com, she writes a biweekly blog at http://insidestorey.blogspot.com that comes out on Tuesdays.

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