What is pain?
Pain is a vital defense mechanism for all animals. After all, to stay alive, animals need the ability to sense something potentially harmful to the body, react to it, and learn from it. Therefore, pain changes the physiology and behavior of the animals. These changes are appropriate. They are designed to prevent further damage, promote healing, and warn others. But as useful as pain is, it causes a stress reaction in the body. Thus, pain can be very harmful to the horse, especially if it is strong or lasts a long time.
Pain is accompanied by pain sensation and pain experience. The sensation of pain causes momentary changes in behavior by which the horse tries to withdraw from danger. Pain experience, on the other hand, refers to the unpleasant emotional state usually associated with the sensation of pain, which also causes longer-lasting changes in the animal's behavior.
An example of the pain sensation is when a filly staggers back and immediately pulls her hooves away after a swan feeding at the spring pasture pecks it hard. The experience of pain, on the other hand, means that when the filly feels pain, it moves away from the bird, gets close to her mother, shakes her head, rubs her hooves, and neighs in frustration. She can also use her behavior to signal to the other foals in the herd that the white bird is dangerous. Later, she gets anxious whenever she hears the sounds of the swans. After years, she will also prevent her own foal from getting too close to the white dangers.
The pain experience is not always the same
Many different things influence the pain experience produced by the brain in the horse itself and its environment. Therefore, the pain experience is always individual and very complex. First, the detailing and descriptive part of the pain experience tells where the pain is, how hard it is, and how long it lasts. The second part is related to the unpleasantness of pain and the negative emotional states and suffering it causes. The animal tries to avoid pain and get rid of it. In addition, the animal learns from pain, and the experience of pain changes the animal's behavior for a long time. Previous experiences, mood, and, for example, fear and anxiety can also affect how the horse experiences pain.
The experience of pain depends on how the horse's brain interprets the conditions related to pain. That's why a horse can experience very different pain in different situations, even if the cause is the same. For example, a vaccination. And that's why different horses experience a needle stick in very different ways. The emotions experienced by the animal and what it has learned in the past greatly influence what the brain decides to do in relation to the perceived pain. Therefore, the behavior caused by pain can also be very different depending on the circumstances and the situation. For the same reason, the pain symptoms of a horse experiencing long-lasting pain vary from time to time.
When thinking about pain and its alleviation in horses, it is essential to understand that the experience of pain is always a product of the brain. So, it is almost always not the same as impending or actual tissue damage. Rather, pain experience indicates the level of danger interpreted by the horse's brain. This is because the most important function of the brain is to keep the horse safe and alive. That's why the brain constantly processes danger and pain messages from the body, interprets them according to the situation, and compares them with other sensory information available as well as in connection with previous experiences and prior learning. Then, the brain decides about how threatening or harmless the pain messages are.
If the danger perceived by the brain is great, the pain experience is usually strong. Conversely, if the brain interprets the danger as low, it usually produces a mild pain experience. At the same time, the brain decides what to do in relation to the danger and pain.
Pain is different
Pain can be divided according to duration into either acute short-lasting or persistent long-lasting pain. Short-lasting pain primarily has a protective meaning for the body and has an apparent reason. It warns the animal of danger and thus prevents further damage. The animal avoids pain, and further damage is prevented. The first phase of the pain is short in duration and sharp in nature, and it is easy for the animal to localize it. For example, when a horse steps on a sharp stone, it quickly pulls its hooves away from the impending danger.
In the second phase of the short-lasting pain, after the damage to the body, for example the hoof, begins to heal, the pain is more profound and spreads more widely. This pain prevents further damage and promotes healing. The horse sensitizes and takes care of the damaged area and its surroundings, for example, a horse with a wound in its hoof is lame. Moreover, when the hoof heals, the pain also decreases and stops. Thus, short-term pain is related to an injury or illness and eases as the body heals. Sometimes, however, the pain is prolonged or lasts a very long time. Then, the pain is no longer related to the damage in the body and, therefore, does not protect the animal. If the pain continues for a long time, it also usually gets worse and starts increasing on its own.
Different things cause pain to horses in different ways. For example, inflammation is accompanied by nociceptive pain not only because of the neurotransmitters of inflammation, but also because the site of inflammation swells and stretches due to the fluid accumulation. This accumulation of inflammatory secretions is especially painful in places surrounded by inelastic tissues, such as in a joint or inside the hoof. They have little room to expand, so the pressure builds up quickly. That's why, for example, arthritis and hoof abscesses cause very intense pain for horses. Neuropathic pain is the result of an injury to the nerves. Nosiplastic pain, on the other hand, is caused by changes in the functioning of the body's pain-sensing and pain-experiencing system.
Pain can also be divided into somatic and visceral, i.e., pain arising in the internal organs. Somatic pain occurs in the skin, bones, and muscles. Visceral pain, on the other hand, originates from the internal organs. Visceral pain is dull and difficult to localize and can radiate to the horse's skin.