Stress & Horse Health

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How Stress Affects A Horse’s General Health

Signs of stress in a horse can be subtle, so they can be overlooked or even misinterpreted as behavioural problems. If stress is not identified and addressed, a horse’s performance and health can be affected.


Many causes of stress in horses relate to a change in routine or environment. These changes can include feed, bedding, pasture and pasture mates. Other common causes of stress include the deprivation of natural behaviours such as locomotion, social behaviours, and grazing or consuming forage. Additionally, horses can experience stress during handling, training, or riding if the learning theory is applied incorrectly. Even small and seemingly insignificant changes can cause stress.

Stress is defined as the symptom resulting from exposure to a situation or environment that is not normal for an animal. Stress can often be seen when animals are handled and/or transported.

Causes of Stress

Response to stress

Inconsistent or infrequent feeding schedule

Horses can spend a significant amount of time grazing. When a horse is in the pasture, it will follow its natural inclinations. 

Horses have evolved to forage and consume forage continuously throughout the day. Forage should be provided as frequently as possible to satisfy the horse’s behavioural, digestive, and health needs. Horse owners should consult with their veterinarian about feeding horses with special dietary needs, such as obese horses or horses with metabolic conditions. 

Feed should be of good quality and provide nutrients that horses need. 

Minimal exercise

Regular and frequent opportunities to exercise can reduce stress. However, horses should also not be overworked.


Boredom can cause stress and result in stable vices, such as weaving or cribbing. Opportunities for exercise and socialization can help with boredom. 

Isolation or loneliness

Horses are herd animals and get support and a sense of security from their herds. If a horse has no pasture or stall mates, it can get lonely and that loneliness can lead to stress. Horses can be stabled together and be provided with increased turnout time so they have opportunities for contact or are in sight of other equines. 

Unfamiliar environments or changes and differences with familiar routines

Horses have a natural sense of curiosity which can be stimulated by the smells, sights and sounds of a healthy environment. However, they may get stressed if they experience too many sudden or dramatic changes in their environment or increased stress levels in their handlers. Unfamiliar routines that cause stress can even be caused by a visit from a farrier or veterinarian. 

Lack of Access to Forage 

The feeding patterns and diet of domestic horses can vary significantly from free-ranging horses due to human management. Horses evolved as trickle-feeders, browsing and grazing on forages for significant periods (approximately 16-17 hours) during the day. 

Feeding practices that do not support natural feeding patterns can result in digestive anomalies and stress in horses. 

Lack of Opportunity for Locomotion

In natural conditions, horses spend a large portion of their day walking and grazing or browsing for grasses and other forage. They can travel many kilometres per day and engage in many different locomotive behaviours during play and other social interactions. Confinement in stalls or the restricted movement of horses can create stress and the development of stereotypic behaviours.

Horses need the opportunity to freely locomote outside of riding or training.

Social Isolation

Horses have evolved to live in groups with complex social relationships. Social isolation and confinement can cause stress in horses. The abrupt separation of horses may result in distress behaviours. 

Prolonged confinement or isolation, where horses are housed individually with minimal or no social contact, is associated with the development of stereotypic behaviours, such as weaving and stall walking. 

Unfamiliar Environments 

A significant portion of the horse’s brain is comprised of the amygdala, which is the part of the brain that generates a fear response. Horses are naturally neophobic, or afraid of new objects or environments, so it’s important that they are introduced gradually to new situations. 

Riding, Handling or Training

Minimal force or pressure should be used when interacting with horses. The use of punishment should be avoided, as this can generate a significant fear response. Horses have an excellent memory and will remember a negative experience for a long time. Horses learn best when they are relaxed, which can be accomplished by using a minimal amount of pressure and positive reinforcement.

LINK: Read the International Society for Equitation Science (ISES) position statements on the principles of learning theory in equitation to learn more about appropriate interactions between people and horses


Stress can cause health issues in horses. However, stress can often be identified and controlled. Stress will trigger a “fight or flight” reaction, caused by the release of the cortisol hormone. Frequent release of cortisol can affect the horse’s digestive, reproductive, immune and cardiovascular systems, and can cause diarrhea, gastric ulcers and colic. It can also affect the horse’s behaviour.

Cortisol is a hormone that affects tissues throughout the body.

Continual stress causes the regular release of cortisol. This decreases the movement of glucose from the bloodstream into muscle cells, which is meant to conserve blood glucose for functions like brain activity. However, it does decrease the availability of blood glucose for working muscles, which can decrease athletic performance.

Frequent cortisol release can also affect a horse’s immune system and affect tissue healing. This means that stressed horses are more susceptible to infection and respiratory diseases and can be slower to recover from injuries.

Signs of stress can be similar to signs a horse shows when it is ill or in pain. A veterinarian should be consulted to ensure that signs and symptoms are not caused by a medical problem.

There are different signs of short-term or acute stress in horses. These can include:

  • Frequent whinnying or squealing
  • Shying
  • Restlessness
  • Tense muscles
  • Carrying the head high
  • Pawing
  • Elevated tail and tail swishing 
  • Frequent head tossing
  • Elevated heart rate
  • Flared nostrils and snorting
  • Shaking, sweating, or trembling. 

Watch this short video by Dr. Andrew McLean who explains how to recognize signs of stress in horses:

Long-term stress can increase the horse’s risk of behavioural problems, including:

  • Changes in disposition or attitude
  • Decrease in appetite or feeding habits, including picky eating
  • Unpredictable reactions, including bucking, bolting or rearing
  • Depression or lethargic behaviour
  • Defensive behaviour or aggression.

Horses that experience chronic stress are susceptible to developing stereotypic behaviour. Stereotypic behaviours are highly repetitive behaviours that have no obvious goal or function. Some examples of stereotypies in horses include cribbing, box or stall walking, tongue sucking, and weaving. Horses that are cribbing will bite with their incisors on an object like a fence post or stall door, arch their neck and suck in a large amount of air. Horses that weave sway their heads from side to side and may also shift their weight from one foreleg to another. Horses that box walk repeatedly pace back and forth or in circles in a continuous pattern around their stall and seem unable to stop. Tongue sucking is seen when a horse holds their tongue against the roof of its mouth and sucks on it often for several minutes at a time. Stereotypies are the result of suboptimal conditions or stressors in the horse’s environment and the horse has attempted to cope with the stress. Stereotypic behaviours are an attempt to satisfy an underlying need that the horse has been deprived of for an extended period of time. For example, a horse that is prevented from adequate exercise and freedom will often box walk or weave in an attempt to satisfy its need to move. Preventing a horse from expressing a stereotypic behaviour, such as a cribbing collar or anti-weaving bars, can actually worsen a horse’s welfare as they can no longer perform the coping mechanism they have developed. Therefore, it’s essential we provide horses with opportunities for foraging, social interaction, and locomotion to prevent these behaviours from developing in the first place.

Once stress has been identified as a cause of problems, it is helpful to keep a record of the triggers that cause reactions and behaviours.

Stress can often be addressed through simple changes in training or in the horse’s environment, including something as simple as a new stable layout. Mirrors in the stall are sometimes used to simulate social contact if horses cannot be stabled in sight of each other. Anti-weave grills can also help with weaving. Forage can be placed around the stall or in hay nets to simulate grazing and reduce box walking. Horses should be provided with good quality feed on a consistent schedule. Regular turnout and exercise opportunities for locomotion are essential. 

What does the Code of Practice for the Care and Handling of Equines say about turnout, exercise and social opportunities?

“For the purpose of this Code, turnout means allowing horses “free time” (i.e., not under controlled exercise) in a dry lot, arena, pen or pasture. Turnout does not necessarily mean the horse is grazing. Exercise refers to physical activity (indoors or outdoors) and includes, but is not limited to, walking-in-hand, riding, lunging and hand grazing. Social opportunities refer to occasions when horses can interact with other horses via sight, sound and/or direct contact. Horses are highly adaptable to many weather conditions – keeping them outdoors or giving them frequent outdoor access is encouraged. There are several advantages to providing horses with turnout and social opportunities. Research shows that horses with turnout time have greater bone density than those that are strictly stalled. Horses with increased turnout and social opportunities have also shown themselves easier to train and handle. If given ample social opportunities (either turned out with other horses or group-housed), horses learn training tasks more efficiently and perform fewer undesirable behaviours (e.g., biting, kicking, bucking) compared to stalled horses. For a small percentage of horses, turnout may bring a risk of injury (depending on their temperament and whether they are accustomed to turnout). These horses may need to be transitioned to turnout over a period of time (e.g., transition from a stall to a small paddock and then to pasture).”

The following requirement is identified in the Code of Practice:

Horses must have some form of exercise or turnout unless under stall rest for medical reasons or severe environmental conditions make this temporarily impossible.

These recommended practices are also provided in the Code of Practice:

  1. Turn horses out with other horses or other equine companions.
  2. Allow daily exercise or turnout opportunities, ideally outdoors and with foraging opportunities.
  3. Build or renovate facilities to allow ample social opportunities (e.g., group housing or stall design that allows horses to have visual or tactile contact with other equines). 
  4. Provide stall-bound horses with continuous access to enrichment devices (e.g., trickle feeders, nibble nets, horse toys).

What does the Code of Practice for the Care and Handling of Equines say about stereotypies?

“Stereotypy (formerly referred to as a vice) is an abnormal behaviour that serves no apparent function and is performed in a repetitive, invariant way. Common examples include weaving (side-to-side swaying of the head, neck and forequarters); cribbing/wind-sucking (the horse grasps an object with its teeth and makes a grunting sound); and stall-walking (circular or patterned route-tracing inside the stable). Wood chewing, not usually classified as a stereotypy, can precede the development of other oral stereotypies and involves stripping and apparently ingesting wood surfaces. Working to prevent stereotypies is generally more effective than trying to “cure” the behaviour once developed. Stereotypic behaviour is most appropriately addressed via management changes that address the underlying cause of the stereotypy. Suggestions include providing ample forage and allowing stalled horses to have visual and tactile contact with other equines. Preventing the horse from performing the stereotypy without addressing its cause may lead to further stress, frustration, and the emergence of other stereotypies. A horse may continue to perform stereotypies even after the predisposing factors have been addressed. This does not necessarily indicate their current welfare status is poor.”

These recommended practices are provided in the Code of Practice:

  1. Minimize the risk of stereotypies by ensuring horses have ample turnout time and opportunities to forage and engage in social opportunities with other equines (these factors seem to be associated with equine stereotypies).
  2. For horses with stereotypies, strive to address the underlying cause of the stereotypy (rather than physically preventing horses from performing the behaviour).
Excerpts from the Code of Practice for the Care and Handling of Equines (2013) have been used with permission, Equine Canada and the National Farm Animal Care Council. The process for the development of Codes can be accessed through the National Farm Animal Care Council.

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