br Conclusion br Acknowledgments br Introduction Throughout

Conclusion
Acknowledgments
Introduction Throughout history, there is literature that supports the notion that animals can be perceived as “healing”. Overall, there is an increased interest in the general field of Animal Assisted Therapy (AAT). Though the field of equine-facilitated psychotherapy is still relatively new, a comprehensive body of evidence does exist in the literature, to support the use of animal-facilitated therapy, not specific to horses, but including work with horses, as an effective treatment for people with depression, anxiety, attention-deficit/hyperactivity disorder, conduct disorders, dissociative disorders, Alzheimer's disease, dementia, autism, and other chronic mental illnesses while reducing blood pressure, heart rate (HR), and levels of anxiety. It is also important to note that the use of AAT has had success in aiding in treatment of several physical diseases such as AIDS, rheumatoid arthritis, and cardiovascular disease. Patients who experienced AAT demonstrated a quicker recovery in comparison with patients who did not interact with therapeutic animals [1], [2], [3], [4], [5], [6]. Equine-Assisted Activities and Therapies (EAAT) is an ever increasingly popular modality for people with mental and physical disabilities with over 800 certified member centers and 4,800 certified instructors offering these programs to help more than 66,000 children and adults (including more than 6,200 veterans and active-duty military personnel) involving horses [7]. With the increase in the number of horses being used in EAAT programs and with the increasing concern for animal welfare, it is important to understand the impact of such interventions on the stress level and quality of life for the horses involved. A sampling of horses of different breeds and those participating in different equine-related activities found that horses used in therapeutic riding programs demonstrated the highest amount of stress as indicated by plasma SP 141 concentrations [8]. Human–animal interaction (HAI) has been investigated for its effects on hormonal indicators of stress such as cortisol, epinephrine, and norepinephrine [9]. The physical and psychological health challenges that participants in EAAT have may result in increased psychological or physical stress on the horses. A recent study hypothesized that therapeutic riding lessons would be more stressful than a standard lesson program with an experienced rider to the horses due to the nature of the physical and psychological challenges of the riders which could interfere with their ability to ride a horse [10]. There is an ever-increasing concern in society regarding the welfare of animals. Stressors are defined as environmental stimuli that lead to an imbalance of homeostasis. Responses to such stimuli include behavioral changes, reduced immunocompetence, and activation of the hypothalamic-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS) [11], [12]. Long-term activation of either neuroendocrine axes has been shown to be harmful. Whether a stressor has adverse effects or not depends not on the stressor itself (intensity, duration, frequency, and so forth) but whether or not the animal is accustomed to the stressor and can predict and control it [13]. In a study performed in show jumping horses of different experience levels, it was shown that horses with more experience, that were used to traveling to horse shows, demonstrated lower cortisol concentrations than their more inexperienced counterparts [14]. It is important to note that stress responses in the short term can help an organism to cope with its environment and challenging situations. If activated chronically, it may have detrimental effects resulting in impaired biological functions. Glucocorticoids and catecholamines are secreted by the adrenal gland shortly after the stressor which can be either physical or psychological. Glucocorticoids have been widely used in animal welfare research as an animal-based assessment of welfare. Activity of the ANS can be evaluated indirectly by heart rate variability (HRV) [15].