ALL STRESSED OUT and nowhere to go
Right about now may be a good time to talk about the fascinating topic of stress. What is it, what causes it and what problems does it cause, what can we do about it?
Stress is both a noun and a verb. As a noun it is simply defined as pressure or tension. Physiologists say it is how the body reacts to a stressor - a stimulus, real or imagined, that causes stress. So stress is both a cause and an effect. It can be considered as “good” (adaptive or eustress) and/or “bad” (causing pathology or distress). Biological stress, is the body’s reaction to external (environmental) and internal (psychological) conditions. Conditions that cause the systemic reaction called stress can be acute or chronic, real (physiological) or perceived (psychological). In other words, stressors can be anything that upsets psychological or physical homeostasis. The stress reaction is a multi system response driven by the autonomic nervous system, it includes the myriad of ways that the body attempts to re-establish equilibrium. Basically, living is all about stress and our response to it. When either physical or psychological balance is disrupted the body responds by immediate activation of the autonomic nervous system. The two main components of the ANS, the sympathetic (fight or flight) and the parasympathetic (rest and digest) mechanisms work in concert to appropriately react to the stress and then re-establish baseline homeostasis. Since life continually presents stimuli that knock us off balance, the stress response is a primary biological coping mechanism for staying alive.
So how did a basically good thing develop such a bad rap for causing disease and distress? The term stress had none of its current connotations of suffering prior to the 1920’s. That might be one hint that external conditions can change more quickly than organisms can adapt. Where a strong fight or flight response was once imperative for survival, that same response may now be excessive, with residual consequences causing pathology within the body. We know that there is variation among species and between individuals in their response to stress. Some animals are more hardy than others, which may also reflect ongoing biological adaptation. The horse as a species has experienced profound shifts in lifestyle and nutrition since domestication which may or may not be related to their relative sensitivity to the effects of stress. However that plays out over time, the relevant challenge for us now is to understand what exactly is happening in the body so we can effectively deal with the consequences and to develop coping strategies for healthy coexistence with chronic stress in ourselves and in our animals.
In horses there is a well established link between stress and gastrointestinal ulcers. Studies suggest that 50% to 90% of horses in sport may have stomach ulcers, but GI ulcers can affect any age or any breed. An activated autonomic nervous system kicks into gear multiple chain reactions that include nervous, endocrine and immune processes within the body. All of these vital functions affect the GI tract in different ways, from increased acid production to decreased ability to heal wounds. There are also anatomical characteristics of the equine GI tract that may contribute to the development of ulcers. For example, the horse was designed to eat small amounts of food throughout the day so its stomach is relatively small and sees a constant secretion of acid. Modern husbandry practices often leave the horse’s stomach empty for long periods with no feed or saliva to buffer the 24/7 flow of acid. High carbohydrate feeds produce volatile fatty acids that also contribute to ulcer formation. Exercise itself increases gastric acid secretion and especially on an empty stomach, may cause a “splash effect” where fluid contacts upper segments of the stomach not designed to withstand exposure to strong acid. (The upper, non-glandular stomach lining lacks the mucus and bicarbonate that buffers and protects tissues in the lower, glandular segment of the stomach.)
Stress factors are also high on the list of contributing causes of GI ulcers. Sometimes these stressors are obvious and often they are not. Obviously, performance horses experience more disruption to their daily schedules than horses that stay home. Training itself requires fine tuning to produce enough good stress (eustress) to improve performance but not enough to cause distress. Not so obviously, every horse responds differently to the pressures of life and their personality may significantly impact their body’s response to stress. While we often consider the mellow, quiet “introverted” horse a lower risk for ulcer formation compared to the reactive, excitable “extrovert”, that may not always be the case. In fact, it might be just the opposite, so it’s incredibly important to know your animal and pay careful attention to their moods and responses to daily living. It’s often a change in the usual attitude, reactions and performance of an individual, rather than their baseline personality, that signals a problem with GI ulceration. An external factor that also increases the risk of developing gastric ulcers is treatment with NSAIDs (non steroidal anti inflammatory drugs) such as phenylbutazone (bute) or flunixin meglumine (banamine). Clinical signs of ulcers in horses range from seemingly normal, to subtle behavioral changes or signs of discomfort, to intermittent colic. A definitive diagnosis of gastric ulceration is obtained by gastroscopy, the insertion of a flexible fiberoptic gastroscope through the nose and into the stomach where tissue damage can be directly visualized.
With such a high incidence of this disease, it’s likely that your performance horse (or any horse) has had or will experience GI ulcers sometime in their life so how can we help them? We can start with feeding and nutritional management; giving small meals at frequent intervals or free choice grass hay, minimizing high carbohydrate diets, feeding alfalfa hay prior to work (its high levels of calcium increases buffering capacity and decreases the “splash” effect of acid in an empty stomach). Keeping a training journal can be helpful to chronicle changes in attitude and performance that may signal more than just a bad mood or estrous cycle. You can bet that travel, disrupted feeding schedules, changes in feed, changes in training and showing cause stress in all horses. The adage that “it’s not what life throws at you, but how you handle it that counts” is true on a psychological and a physiological level and may dictate whether or not horses (or their humans) develop GI ulcers. Since it’s impossible to completely eliminate chronic stress from our lives, it’s fortunate that research has given us a pharmaceutical approach to prevention and treatment of GI ulcers in the horse. The drug omeprazole which stops gastric acid secretion has proven efficacy for the treatment of ulcers and also as a prophylactic to decrease their formation. Omeprazole and the histamine blocker ranitidine are the only drugs approved by the FEI for use in horses in sanctioned competitions. Omeprazole is available as a paste in formulations geared to treatment, Gastroguard and to prevention, Ulcerguard of ulcers. While the drug is relatively expensive, be aware that other brands and formulations that sell at cheaper prices have been shown to have less efficacy. Antacids, commonly used to treat human ulcers are mostly impractical for the horse due to dosage requirements (6 to 12 times per day) but they are sometimes used in combination with drugs that decrease acid production. Histamine blocking drugs partially block acid secretion and must also be dosed several times per day. Coating agents like sucralfate are sometimes helpful to treat active ulcers by directly protecting the stomach lining tissue. With the plethora of supplements being marketed today, be aware that offering a “cheap fix” is rarely successful when it comes to treating active disease and may cost more in the long run.
Remember that stress linked disease is manageable! One of these days we will be back in the show ring with our horses, so take advantage of this extra time to contact Rocky Bay Equine and discuss possibilities for prevention and treatment of gastric ulcers in your horse.