Stress often has a negative connotation for people. If you are under stress, you are experiencing too much tension and that would be bad and unhealthy. But that is not always necessary, stress can be useful and in some situations even necessary to survive.  

Stress originates when an animal or a person is in a situation that is unpredictable and/or uncontrollable to them. They have no idea what is going to happen at that moment, and are not able to influence the situation (enough). The animal then experiences a condition of (severe) psychological and/or physical pressure. For instance a foal being weaned or a horse being transported on a trailer. Stress can be caused by external stimuli (from the environment) or internal stimuli (from within the animal). These stimuli are also called stressors. When an animal is exposed to these stressors, all kinds of physiological processes kick in; this is the stress response. 

Acute stress
Initially, the animal will experience acute stress; the stress response is very effective here and ensures that the horse reacts appropriately. For instance, a horse that is spooked by a plastic bag in the hedgerow will run away, removing itself from the stressful situation. Acute stress only lasts a short time, and is not harmful. On the contrary, it is vital to the animal’s survival, but also to learn new things. Acute stress releases among others the hormone adrenaline. This hormone causes a number of reactions in the body: the heart rate, blood pressure and breathing go up, muscles contract, the pupils dilate and the animal may start sweating. In addition, it ensures alertness and the release of extra energy needed for the fight-or-flight response. 

Horses are flight animals by nature, in situations of acute stress they will always be more inclined to flee than to fight. You should take into consideration that each individual horse responds differently to stress, some will bolt, but some will also freeze or rear. Be aware of this in your training. 

Chronic stress
When stress persists for a longer period of time, acture stress changes into chronic stress. This type of stress can be harmful to the horse’s health and welfare. Stress hormores will continue to be released into the body and the animal is not able to adapt (sufficiently) to the situation. One of the harmful consequences may be a weakened immune system, putting the horse more at risk of diseases. It can also increase the chances of heart conditions and adversely effect growth and reproduction. The horse might start to exhibit stereotypical behaviour, like cribbing or weaving. Stereotypical behaviours are repetitive, compulsive movement patterns that at first sight seem to have no logical function. 

What can we do about stress?
Acute stress cannot really be prevented. As mentioned above, it is vital to a horse’s survival to deal with stressful situations. What you can teach a horse is how to deal with acute stress. The horse’s instinct in cases of acute stress will tell it to run! In domesticated life with humans, this can lead to dangerous situations. This makes it very useful to teach your horse that a better response would be to stand still instead of bolting. 

It is very important to prevent chronic stress by meeting the horse’s natural needs as much as we can. Ensure sufficient social contact and free movement (preferably in a field or paddock). Feed little and often (or offer unlimited roughage) to prevent boredom and keep the horse’s intestinal tract in optimum health. Carefully consider your horse’s stabling, ensuring plenty of space and light. This all decreases the chances of chronic stress and ensures your horse’s well-being.