**5. Indicators of equine stress**

Information on equine stress levels is important when evaluating many aspects of horse management, training, and the treatment of different diseases. It is apparent that great effort is being made to improve recognition and quantitative evaluation of stress in horses. Various testing techniques are used to measure stress responses in horses, which can be roughly divided into visual, clinical and laboratory, or noninvasive and invasive methods [182]. Behavioral indicators of stress responses are very different, and very well described [183, 184]. In an attempt to quantify visual changes equine stress, the **"**The Horse Grimace Scale" (HGS) has recently been used, which is fine-tuned for detecting equine pain, but no validated grimace scale for detecting fear or anxiety exists yet [184].

#### **5.1 Clinical signs of equine stress**

Clinical signs of disturbance of the sympathovagal balance can be used to assess acute equine stress which primarily includes changes in cardiovascular parameters,
