Champing at the bit: How one piece of metal may threaten a horse’s health

3 Jun 2020

Sandra Hurley, UL. Image: FameLab Ireland

The use of a bit in horse riding to control the animal’s movement may be seriously impacting its health, according to UL researcher Sandra Hurley.

Originally from the Netherlands, Sandra Hurley previously worked in primary schools as a trained artist. She then decided to follow her passion for science and horses at the University of Limerick (UL), where she received her BSc in equine science as a mature student in 2017.

Hurley is now a PhD student at UL doing research into the effect of the bit on equine behaviour, welfare and physiology. Earlier this year, she was a participant in the finals of the FameLab Ireland science communication competition.

What inspired you to become a researcher?

I have always asked questions, since I was a young child. My parents kept a list with my most interesting questions and gave me a subscription to a science magazine for children at the age of  six.

Can you tell us about the research you’re currently working on?

The use of a bitted bridle has been the principal method by which the ridden horse has been controlled since the Bronze Age. Bits are fitted within the mouth and apply pressure to several different points in the oral cavity: lips, tongue, interdental space, hard palate and lower mandible.

Due to the lack of space in the oral cavity, the use of the bit is invasive. To communicate with a horse, signals are transmitted to the bit via varying rein tensions. It has been demonstrated that horses will not voluntarily go over a certain rein tension to gain a food reward. As rein tension increases, horses show various behaviours to escape pressure from the bit.

Bit pressure can lead to oral trauma in the form of lesions and ulcers in soft tissues and the formation of bone spurs on the interdental space caused by periostitis.

Generally, no comparable damage is found in wild equids. The horse is an obligatory nasal breather, with oral breathing only occurring under abnormal conditions. Due to the anatomy of the equine nasal and oral cavity, the bit could potentially impede respiration by obstructing the upper airway.

As the bit has the potential to cause horses serious harm and distress, use of the bit in equitation is a potential welfare issue and, at a time when public perception of animal welfare is growing, the effect of the bit needs to be explored further.

In my research, I examine the effect of the bit from different perspectives: physiology, biomechanics and behaviour.

I evaluate the performance of horses during standardised exercise tests wearing both bitted and bitless bridles, using specialised equipment such as inertial motion sensors and heart rate monitors.

This allows me to compare the effect of the bit on physiological parameters such as heart rate, heart rate versus velocity, recovery time, as well as biomechanical parameters such as stride length, joint angles, and head and neck position.

In your opinion, why is your research important?

In equestrian sports, the horse and human form a unit, but the main athlete is the horse. It is the power, speed or the gymnastic efforts of the horse which determine the performance; the role of the rider is to skillfully direct the horse.

The rider controls the horse by the use of a bridle and a metal bit inserted in the horse’s mouth. As the mouth is one of the most sensitive parts of the body, the use of the bit can cause the horse considerable harm. Previous studies have shown that competition horses have a high incidence of oral lesions and ulcers. Use of the bit is therefore a potential welfare issue.

I am deeply interested in the science of equine health, behaviour and welfare. More specifically, how the scientific evaluation of factors that affect the ridden horse can improve welfare. Equine welfare can be compromised when the horse’s natural adaptations are challenged.

Many horse management practices were put in place for human convenience, but cause physical, social and environmental distress to horses.

What are some of the biggest challenges you face as a researcher in your field?

Equestrian sports are steeped in often centuries-old traditions, many of which are upheld without questioning. Concern for horse welfare has led to certain practices in the equine industry, such as use of the whip and the bit being called into question, but largely from outside the equine industry.

Use of the bit is ubiquitous in equestrianism and even compulsory at competition level in most disciplines. Furthermore, many riders are averse to the idea of riding horses without a bit, as the bit is perceived as a necessary tool to maintain control of the horse. This is in spite of evidence that use of the bit does not stop flight behaviour in horses leading to loss of control.

What are some of the areas of research you’d like to see tackled in the years ahead?

Horses are social animals, but we tend to keep them housed in individual stables. This is an area where more research is needed. This is a time of human social distancing and self-isolation, and as a social being humans find this hard to cope with. However, this is how horses are normally kept.

Are you a researcher with an interesting project to share? Let us know by emailing with the subject line ‘Science Uncovered’.