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Stress: The Good, The Bad, and The Ugly
Stress: The Good, The Bad, and The Ugly
Stress is a term often used in daily language, and it is now a well-researched subject. Stress affects individuals in many ways throughout its life. A common misconception is that all stress is bad, but stress can also be good (1, 2, 3). In itself, "stress" is a neutral term to describe some sort of heightened state of emotion. A horse being chased by a predator is stressed, and two foals playing in a field are stressed. These two situations, however, are very different and describe the different ways an animal might experience stress. Although stress can be a result of either good or bad states, it can look very similar. For example, Bucking is a method of self-defense, and is often seen during times of pain or distress (4, 5, 6). On the other hand, it is also commonly seen as a Play behavior (5, 6). To determine what type of stress a horse is experiencing, context is key!
Distress
Distress
Distress occurs during a negative emotional state, like being separated from the herd. A horse in distress may show a variety of the behaviors discussed on this website. In the video above, the horse is showing signs of distress through the facial expression (most notably Mouth Gaping), and it is very tense throughout the body (4, 5, 6, 7). Relaxation is essential for muscle development in exercise, and it a pillar in horse training to develop an equine athlete (8). Tension prevents the muscles from developing, and it can create a false frame, in which the horse is not carrying itself appropriately and is using the wrong muscles for movement (9). This situation can set the horse up for serious injury!
Distress does not occur only during training, though. A horse can experience distress whenever a stressor is present. If a horse's ears are sensitive, a windy day might cause a big reaction. This type of behavior is important to keep track of. In a healthy state, a horse's behaviors will remain generally consistent, but during pain or distress, a horse may react unpredictably. This is especially true with the traditionally trained horse that has learned to work through pain.
Eustress
Eustress
Eustress is connected to positive associations and emotions. A horse experiencing eustress can show many of the same behaviors as a horse in distress would, but the context and certain behaviors will tell you whether the horse is having fun or is panicking (4, 5). For example in the video above, the horse is running around, rearing, bucking, and holds its head high. The horse is experiencing some kind of stress. As it runs up to other horses, it shows no threats of bites, strikes, or kicks, and then it runs away. It does not seem to be focused on getting away from anything in particular. It bucks seemingly randomly. This horse seems to be playing! Play is an essential aspect in a horse's development for survival and reproduction by allowing the horses to practice behaviors and skills that will help with self and herd defense (5, 28).
Eustress is also commonly seen during feeding and turnout time, when the horse is anticipating something good to happen. If you have a good relationship with the horse, it may show signs of eustress or excitement when it sees you!
Effects of Stress
Effects of Stress
Why is this important to know? Stress can affect a horse's body in so many ways from increased heart rate to ulcers (10-16). The beginnings of research into stress looked into how stress affects products. Most notably, research and meat quality decrease when the animal experiences stress during procedures. These discoveries opened a broader discussion to how stress affects an animal. In humans, we already knew that stress decreases our ability to learn and perform (13). Have you ever struggled in class because you were stressed about something? Did it seem like you just could not absorb anymore information, and you were reaching your limit? Well, animals experience the same feeling when they're stressed! Research into horses specifically confirmed the theory, and we can now see just how stress decreases quality of life all the way down to the cellular level (10, 14-16).
Stress influences:
Digestive Health (14-16)
Stress can cause ulcers!
Heart Rate and Blood Pressure (10, 14)
Breathing (10, 14)
Muscle Contraction/Relaxation (10, 14, 24)
Magnesium, Calcium, and Phosphorous work together to activate and relax muscles.
Learn more about Supplements on the Forage page.
Cognitive Function/Ability to Learn (10, 14)
Stress can actually limit how much an animal can learn in a situation, making LIMA-based practices important!
Social Behavior (17, 18)
Psychological Disorders and Stereotypic Behaviors (20-23)
Stressful events like abrupt weaning or excessive stalling can cause lasting behavioral issues like Cribbing and Weaving.
Trauma (23, 25)
Horses can retain long-term memories from their experiences with humans, forming positive or negative associations with them.
Fight/Flight/Freeze/Fawn Response (4-7, 10)
Trigger Stacking/Threshold
Trigger Stacking/Threshold
In this video, Warwick Schiller, long-time horseman and trainer, explains the phenomenon known as "Trigger Stacking". Trigger Stacking is also referred to as the stress threshold. This occurs when a horse experiences multiple stressors simultaneously or in quick succession, and it reaches its threshold and reacts negatively. Think about a time when a horse you were handling seemingly bucked or reared out of nowhere. From your perspective, the horse reacted out of nowhere and to nothing. From the horse's perspective, it may have been feeling pain somewhere, heard a stressful noise, and saw a stick fall from a tree. Any of those stressors on their own might not have caused the reaction, but all of them put together did. Now, think about a time you were sick or hurt. Did little things make you upset? For example, you dropped something because you had a headache. Would that cause you to react differently than when you feel good?
To avoid Trigger Stacking, it is important to read the smaller stress signs of the horse in order to change or stop what you are doing. Horses will show early signs of distress through non-contact behaviors through Facial Expressions, Posture, and Vocalizations. Escalating behaviors may include some Aggression and Stereotypic behaviors like Cribbing and Weaving.
Flooding and Learned Helplessness
Flooding and Learned Helplessness
Flooding is a practice that takes away all methods of escape for the horse and pushes the horse past threshold to the point of submission or Learned Helplessness. Learned Helplessness is a mental state that reflects a "shut down" demeanor. In this situation, the horse has learned that no matter how much it fights or attempts to escape, there is no way for it to get away from what is making it so uncomfortable (29, 30). This causes the horse to give up trying at all. For the handler, it may seem like the horse is finally learning something, but what it really means is that the horse has accepted death as its only way out, as extreme as it may seem. The effect of flooding using aversive techniques is the main reason we make our default training method Force-Free Positive Reinforcement, which presents the lowest risk of causing Learned Helplessness. Referring to The Three Thresholds picture, we want to keep the horse in the green zone, under threshold. If the horse starts to reach or pass that threshold, take a step back and re-evaluate the situation. There is no shame in ending a training session early!
Least Invasive, Minimally Aversive (LIMA)
Least Invasive, Minimally Aversive (LIMA)
In training and handling animals, it benefits all parties to minimize stress and punishment in any situation. Below is a graphic showing what is known as a Humane Hierarchy of behavior modification and training (26, 27). This Humane Hierarchy was originally developed for dog trainers, but it has been adopted for use in research labs with Primates and zoos with apex predators like Lions. When attempting to change or train a behavior, the first step should be fully vetting the health of the horse. A horse in pain cannot be expected to perform well. Antecedent Arrangements refers to offering or removing certain stimuli to decrease unwanted behaviors while encouraging healthy behaviors, prior to training. For example, a horse that is consistently rearing and bucking in the stall may benefit from increased turnout before attempting to train the horse.
Once those needs are met, Positive Reinforcement should be the default training method for all horses. As we increase the workload we ask of horses, the behaviors may become more difficult to train. Similarly, a particularly stressful event or procedure may not be achievable with only Positive Reinforcement, which is when trainers may move onto differential reinforcements methods to train those behaviors. These methods are more complicated than just Positive or Negative reinforcement alone.
If a trainer finds themselves needing to go to and past "Exit 4", they must stop themselves and decide how important the behavior modification is for the horse's quality of life. Negative Reinforcement relies on an aversive stimuli, something the horse does not like and wants to move away from. This is inherently stressful for the horse, and thus affects not only the training session but also the horse's overall quality of life. If the training is necessary for a medical procedure or in an emergency, it may be acceptable to continue on to using Negative Reinforcement and Negative Punishment. If a trainer finds themselves resorting to Positive Punishment, they should immediately take a step back or remove themselves from the situation completely. Positive Punishment should be avoided and reserved only for life-threatening events, like a dog attack, for example. The use of Positive Punishment is often a sign of unsuccessful training and/or handling, and a trainer should figure out what went wrong and how to prevent the situation in the future.
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