Stereotypies are not seen in feral equines e.g. prezwalski horses. However, they can develop in these feral species once they are captured and confined (11). They are a red flag to mark severe, chronic stress. Stereotypies are an animal's way of coping with the stress of an unnatural environment. 

 

Stereotypies are caused by poor management practices, specifically:

 

Social isolation: 

• Horses who have social contact with other horses are less likely to develop a stereotypy (5).

• In a study weaving stopped when horses had access to other horses on all 4 sides of their stable (2)

• Horses who perform a sterotypie are sometimes socially isolated from other horses so that they aren’t ‘copied’. Stereotypies cannot be copied; the reality is horses in the same stressful environment are likely to react in a similar way. ‘Rather than being picked up from the horses such stable vices may be picked up from the stable itself’ (1).

 

Confinement: 

• As you increase the time spent stabled, so does the risk of a stereotypy being present (12).

• Foals housed in individual boxes are more likely to weave or box walk (16).

 

Frustrated motivations:

• The stereotypy itself is often a clue as to the main stressor that the horse is suffering. Movement related behaviours relate to the horses need to move and are frustrated escape responses (5). Whereas oral stereotypies are more likely caused by an incorrect diet and the behaviours associated with that e.g. not grazing for 16 hours a day.

• Sterotypies are often triggered by stressful/arousing situations, like feed time when the horses goals are thwarted e.g. they want to eat their feed but they are stuck in the stable and cannot walk over to it.

 

Abnormal feeding practices and deprivation: 

• Less than 6.8kg of forage per day increases the likelihood of stereotypes developing (14).

• Wood chewing is partly due to a lack of cellulose in the diet (3).

• Wood chewing increases in high protein diets (18).

• Absence of a salt lick can increase crib-whetting (3).

 

Having no control over their own environment:

• Stereotypies are associated with environments which are threatening and an inability to escape (19).  

• Over or under-stimulation in their environment can increase stereotypies.

• Aversive training causes distress. 

 

Weaning:

• After weaning giving them concentrate feeds makes them four times more likely  to crib-bite and feeding haylage increases the risk of wood chewing (10).

• Foals weaned in social isolation and fed concentrate feeds had level 5 ulceration in their stomach within 2-4 weeks. This caused them to crib-bite in an attempt neutralise their acidic stomach (10).

• Foals abruptly weaned before they are ready are more likely to develop an oral stereotypie due to their motivation to suckle (11).

 

If both parents have a stereotypy this gives the foal an 89% chance of them also developing one (9).  Ideally, we should not breed from horses with a stereotypy. However, genetics is no reason to write off a sterotypie as inevitable. There may be a genetic tendency to develop a stereotypy, however whether they do become a stereotypic horse will depend on their environment and it can be avoided (6).

 

Inside the body:

• Some steroeotypies are carried out as they release pain relieving and feel-good chemicals. (16)

• Gastric ulcers may play a part in crib-biting and wind-sucking as they produce saliva which helps to neutralise an acidic stomach.   

• A lowered heart rate has been recorded in crib-biters while they crib (13)

• Sterotypies show electrical activity in the brain similar to dozing (19).  

• When crib-biting dopamine may activate a reward mechanism (11).

• Crib-biters develop uneven tooth wear making eating difficult and are at risk of colic and a low bodyweight (11).

• Weaving causes damage to the hooves and musculoskeletal system and box-walking in one direction is likely to cause lateralised atrophy and hypertrophy of the lumbar musculature (11).

 

Gadgets, electric shocks and surgery are often recommended as a way of stopping  horses performing stereotypies. These should be avoided as:

• Being unable to perform their steroetypy will cause more stress, as you have removed their way of trying to cope. 

• The gadgets mask the symptoms of the problem; they do not help cure the cause.

• They cause pain or discomfort and are inhumane.

• Horses prevented from performing a stereotypy often become aggressive (5)

• If you stop them performing one stereotypy they may develop a different one (5) e.g. if there is no surface to crib on horses may either crib on their own knee (3) or will wind-suck instead

• They may only exaggertate the behaviour. For example with cribbing, when collars are used and then removed, the horses perform crib-biting at a higher rate than before the collar was fitted (15).