By Hannah Botha, MSc Equine Nutriiton
Stereotypic behaviours are actions that are repeated without any apparent or obvious purpose or function. These behaviours involve a need-related drive that develops if an environment has inadequate opportunities for satisfying the need the horse is trying to fill. Once established, these behaviours may become a need in and of themselves, and the animal repeats the sequence over and over to address this ‘need’.
Abnormal or stereotypic behaviours can be classified into three distinct groups:
- Oral stereotypies – licking, chewing, tongue-rolling, crib-biting or wind-sucking.
- Locomotor stereotypies – pawing, weaving, head-tossing, stall-walking or head-nodding.
- Redirected behaviours – consuming bedding or coprophagy (the eating of manure).
Out of the three groups, research has shown that oral stereotypies have the highest prevalence, followed by redirected behaviour and, finally, locomotor stereotypies.
Concerns about health and performance
Sometimes termed a ‘vice’, stereotypic behaviour should instead be seen as a sign that something is not quite right rather than a defect of the horse’s personality. These behaviours often reflect poor welfare, such as inadequate living conditions or chronic stress.
Stereotypic behaviours performed occasionally might not affect the horse’s health or be of much concern. For example, chewing wood doesn’t necessarily mean a horse will ultimately become a cribber. However, if you notice that a previously infrequently performed behaviour has increased in frequency, you might need to look at ways to change that behaviour before it becomes a habit.
Stereotypic behaviours exhibited for long periods or very frequently can impair the horse’s soundness or ability to perform as an equine athlete. For instance, weavers can develop physical side effects from their actions since they stress their leg joints more through repetitive motion.
Windsucking, on the other hand, can cause stiffness of neck muscles and wearing of the incisors, and current research is looking into the possibility that it causes arthritis of the jaw. Colic and gastric ulceration are often associated with windsucking and crib biting. Still, at this stage, the reason behind this is largely not understood, although it is likely that the amount of time spent performing this behaviour equals a reduced time eating forage, which in itself is known to cause digestive issues. Alternatively, it could be the reverse scenario where crib-biting and wind-sucking occur due to abdominal discomfort. In this situation, the behaviours may be expressed to reduce pain, indicating once again that stereotypic behaviours can act as warning signs of future problems.
A note on windsucking
It was once thought that windsuckers swallowed air, but studies have shown this is not the case. Fluoroscopy and endoscopy were used to observe air entering the pharynx and oesophagus, and it was confirmed that air was not swallowed into the stomach during windsucking (McGreevy et al., 1995).
So, how does fibre help?
Research has shown that the amount of hay fed influences all stereotypies; the risk of abnormal behaviour increases when less than 1.5% of body weight in forage is fed daily.
Recent research looked into reduced fibre diets in more detail, and it was found that the time spent on abnormal oral behaviours significantly decreased in horses fed a high-fibre diet. Oral stereotypies decreased by 70%, and redirected behaviours decreased by 86% (Hanis et al., 2023). Less time was spent performing oral stereotypic behaviours and consuming bedding in the high-forage group.
This study also found that the mean plasma cortisol and ghrelin levels decreased by 30% and 20%, respectively, in the treatment group over the 30-day trial. These hormones are involved in the body’s stress response which supports the hypothesis that oral stereotypic behaviours and redirected behaviours appear to derive from failure in feeding motivation and lack of satiety (Hanis et al., 2023).
The study concluded that high-forage rations provided longer satiety than high-concentrate diets and that diet most certainly influences horse behaviour and hormone levels. Therefore, ensuring horses have sufficient forage in their diet significantly affects overall health and well-being in equids.
Therefore, in horses prone to stereotypies, owners may need to increase the level of forage to above the standard 1.5% of body weight per day. This could mean increasing to 2% or even providing ad-lib forage, but this would depend on the individual. For horses requiring more energy in their diets than provided by hay alone, or for those unable to consume larger volumes of hay, adding fibrous ingredients such as soy hulls and beet pulp, both of which contain higher levels of energy per kilogram than some hays, could be an alternative option.
References
*Hanis, F., E.L.T. Chung, M.H. Kamalludin, and Z. Idrus. 2023. Effect of feed modification on the behavior, blood profile, and telomere in horses exhibiting abnormal oral behaviors. Journal of Veterinary Behavior 60:28-36.
Hanis, F., E.L.T. Chung, M.H. Kamalludin, and Z. Idrus. 2020. The influence of stable management and feeding practices on the abnormal behaviors among stabled horses in Malaysia. Journal of Equine Veterinary Science 94:103230.
P D McGreevy , J D Richardson, C J Nicol, J G Lane 1995. Radiographic and endoscopic study of horses performing an oral based stereotypy. Equine Vet Journal Mar; 27(2):p92-5.