Is your horse in pain?
Pain changes the horse's behavior and facial expressions. Recognizing pain at its earliest signs is a complex but essential skill that should be practiced whenever possible.
As prey animals, horses have developed a high threshold for showing their pain and weakness clearly outward. Horses have very subtle pain behavior that is mainly developed to be noticed by other horses. Pain behavior includes different facial expressions, gestures, and positions. The subtle indicators of pain make it difficult for us humans to recognize the pain the horse is experiencing.
The fact that the pain experience is always individual and dependent on the situation makes it more challenging to recognize the horse's pain and assess the intensity of the pain. In addition, pain is caused by three different mechanisms. Thus, the signs of a horse's pain in its facial expressions and behaviors can vary greatly depending on the cause, the situation, and the individual. Therefore, it can be challenging to recognize and evaluate horse pain, especially if you need to become more familiar with the typical pain behavior of horses.
Three different mechanisms of pain
In veterinary medicine, more attention is paid to the three different mechanisms of pain — nociceptive pain, neuropathic pain, and nociplastic pain — which all cause different changes in the horse's physiology and behavior. In addition, their treatment differs in many different ways.
Nociceptive pain is caused by the damage and inflammatory reaction of the animal's tissues (except the nervous system) and the various associated inflammatory mediators. For example, tissue damage from a wound, bone fracture, or muscle tear causes nociceptive pain.
Neuropathic pain, on the other hand, is caused by injuries and inflammations of the nervous system. So, it is a pain arising from damage to the nerves. For example, a spinal nerve being pinched when the spinal cord is damaged, or a nerve in a limb being severed due to an injury can lead to neuropathic pain. Sometimes, nerves are also damaged because of the disease. For example, changes in the peripheral nerves of the lower part of the leg have been found in horses and ponies suffering from laminitis. Similarly, osteoarthritis can be accompanied by neuropathic pain.
In addition to nociceptive and neuropathic pain, the pain the horse is experiencing can be caused by changes in the functioning of the body's pain-sensing system. This third mechanism of pain is called nociplastic pain. In nociplastic pain, the factors that increase the pain sensation in the animal's body work more efficiently than before, and, on the other hand, the mechanisms that inhibit the experience of pain work worse than usual. For example, the activity of brain areas related to pain experience and the connections between them may be increased in patients suffering from nociplastic pain. Nociplastic pain is also associated with negative emotional states, sleep difficulties, and, for example, problems with learning.
Many pain mechanisms at once
A long-standing pain condition often causes nociplastic pain and is usually present at the same time as nociceptive and neuropathic pain. For example, this can be the case with horses suffering from osteoarthritis. Long-lasting pain can also arise from tissue damage that heals, but the animal still experiences intense pain. In this case, the animal will most likely suffer from nociplastic pain, although studying this type of pain in animals is only at the beginning and is still very difficult.
The fact that the same patient can have pain caused by two or all three different mechanisms at the same time often adds to the challenges of identifying and alleviating pain in a horse. So, we are talking about mixed pain, where the patient's pain experience is simultaneously affected by two or three different pain mechanisms. For example, extreme neuropathic pain quickly causes changes in the patient's nervous system, leading to nociplastic pain. In addition, when the animal changes its way of standing and moving due to neuropathic pain, the abnormal load quickly cause pain in the muscles, fascia, and joints, causing nociceptive pain.
In addition, all three different mechanisms of pain are also associated with sensitization to pain, i.e., the changes that occur in the body that increase the intensity of the perceived pain. So, pain increases pain. That's why quick recognition and alleviation of pain is so important.
Since treating pain arising by different mechanisms is different, it is worth considering what kind of pain the patient is experiencing. The different mechanisms of pain also differ in whether they protect the body. Remember: if pain does not protect, it only harms the animal. Nociceptive pain primarily protects the body, as it prevents further damage and can speed up the healing of the injury when the horse takes care of the healing area. Usually, this pain is related to the size of the damage and eases as the injury heals. However, sometimes, the cause of nociceptive pain, for example, osteoarthritis, does not heal. Then, nociceptive pain can continue for a long time but is still proportional to the damage. On the other hand, neuropathic pain and nociplastic pain rarely have a protective effect on the body, and they are often non-proportional to injury. They are usually only harmful to the animal when the pain burdens the body without the benefit of the protective effect.
Pain changes the horse's behavior
Pain behavior is influenced by many different factors, such as the horse's breed, temperament, training, previous experiences, and the relationship with the handler and other horses in the stable. For example, a timid animal can hide its pain more often than its confident companion. Also, a new and strange environment and, for example, the stress caused by transport can make horses hide the pain they experience.
The situation can also affect the experience of pain. A badly frightened animal can momentarily seem completely pain-free, even if it has been very seriously injured. On the other hand, getting nervous and waiting for pain can worsen the pain experienced by the horse. Focusing on something important, such as taking care of a foal, often masks pain-telling cues in behavior, which should be remembered, especially when caring for a mare nursing a young foal.
The purpose of behavioral changes caused by pain is to protect the body, prevent further damage, promote healing, and warn other horses. The heartbeat accelerates, and breathing becomes fast and shallow. Pain can also slow down or even stop digestion. In addition, pain interferes with sleep, social relationships, and learning.
Changes in the horse's normal behavior often indicate that all is not well with the horse. Pain behavior often depends on what causes the pain and where the pain is felt. Lameness is almost always a sign of pain in the limb. Stepping on a sore leg hurts, and the animal tries to protect itself. When a lame horse walks, its sick leg spends as little time as possible on the ground, and less weight is taken on it than on healthy legs.
On the other hand, visceral pain from the internal organs is a different kind of pain than somatic pain arising in the skin, bones, and joints. For example, colic means pain somewhere in the horse's abdominal cavity. Visceral pain typically manifests as restlessness, kicking under the stomach, pitting, staggering, and sweating. It is common for horses to be sensitive to touching a sore spot, for example, a wound or a contusion. A horse in pain can also look at the sore spot or its flanks. A horse suffering from laminitis stands in a typical sawbuck position because it tries to relieve its pain by shifting its weight from the front legs to more of the hind legs. An animal suffering from severe and long-lasting pain may also try to harm itself by biting or rubbing the painful spot.
Sometimes, a horse suffering from pain seeks more attention than usual from its handler, and the horse can learn how to ask for pain-alleviating medication. Usually, however, pain changes the horse's behavior, causing it to withdraw, be fearful, or become aggressive. In particular, prolonged pain can make the horse angry, and it tries to defend itself. The horse resists actions that cause or aggravate pain by kicking, biting, or attacking people and other horses. Sometimes, constant pain can also cause a horse to shut down. Especially when the animal's changed behavior is not understood to be caused by pain, but the animal is punished for the pain behavior.
The pain face
The pain experienced changes the horse's facial expression. Indeed, interpreting facial expressions is of great help in identifying and evaluating pain. When evaluating facial expressions, attention is paid to six different points on the horse's face. When assessing pain, it is essential to remember that all these changes in the horse's expression can occur alone and also without pain. However, it has been established that the more pain-indicating changes in the animal's expression, the stronger the pain experienced by the animal is in general.
The distance between the ears of a painful horse increases. At the same time, the ear openings are often directed outwards and downwards. The normal position of the ears, alertly observing the environment and moving, is absent. At the same time, the horse in pain has a worried expression as the muscles surrounding the eyes tighten, causing the typical angular shape of the eye. The eye may also be wholly or partially closed. The gaze of a horse in pain is intense and turned inward. The masticatory muscles on the sides of the horse's head also become tense. Thus, they stand out more clearly than usual, creating the impression of a tense look. A horse in pain may also clench or grind its teeth. Similarly, the mouth tightens, and the lips are pressed tightly together. The normally relaxed and round mouth becomes angular in this way, and the lips seem to stretch. In a horse experiencing pain, the nostrils are enlarged, and their shape is closer to a quadrilateral than an average oblong drop. The tightening of the muscles in the head area makes the horse's jawline more clearly visible than before.
In addition to the facial expressions, the position of the horse's body and head can help in pain assessment. A horse typically carries its head high, while a painful horse's head is at or below the level of the withers. The horse's reaction to its environment and the animal's position in the stall also change. A horse typically stands at the front of its stall and follows its surroundings attentively, reacting to an approaching human, but a horse in pain can retreat to the back of the stall and look at the wall. The reaction to events in the environment and the approaching person changes, and the animal seems apathetic.
Pain is sometimes difficult to identify
Perceiving and evaluating mild or moderate pain is significantly more complex than severe pain. It is pretty common that you sometimes have to search for the location and cause of the pain for a long time. For example, mild lameness can be challenging to identify. Eating slowly, dropping feed, and, for example, watering hay before eating can be signs of dental problems. The horse may also behave abnormally when driving or riding. Keeping the mouth open, sticking out the tongue, or biting the bit can indicate pain in the mouth, as well as wagging the tail and resisting aids. Moving the tongue in the mouth is often due to numbness caused by an inappropriate bit.
Reluctance to move is an alarming symptom and is quite often caused by the pain experienced by the horse. Reluctance to work on the small circle can be a sign of pain in the legs, as can a saddle that has moved to one side. When one front leg is very sore, the horse may not want to lift the other leg. That is when the weight falls entirely on the sick leg, and the pain increases.
The pain can also cause restlessness and weight shifting from one leg to another. Nervousness when saddling or brushing can indicate pain in the back. Sometimes, the visceral pain is reflected on the skin. In that case, intestinal problems, such as sand deposits, intestinal inflammation, or a stomach ulcer, can make the touch unpleasant or cause pain in the horse's back, flanks, or hind knees. A common symptom in horses suffering from sand accumulation is sensitive skin on the flanks.
The response to the pain-alleviating medication can also tell the pain experienced by the horse. For example, the lameness stops after numbing a painful joint with a local anesthetic. If the horse is suspected to be in pain and the pain medication given makes it feel better, the patient is very likely to experience pain. On the other hand, the situation is not so clear if the patient does not respond to pain medication. Possibly, the pain medication administered with the given does not work on the pain mechanism in question, or the medication is not enough to relieve or eliminate the pain.
Sometimes, the pain is not noticed until it stops. A Finnish study investigating dental pain in horses found that changes in the horse's facial expression and behavior caused by a sore tooth stopped when the veterinarian removed the sick molar.
Since pain can start slowly and gradually change the horse's behavior, it is essential to know the normal facial expressions and behavior of the horses under your care. You must also be sensitive to changes in the horse's behavior and know how to suspect pain as the reason for them. Early detection of pain is the key to alleviating it quickly.