Researchers have developed a digital device to measure noseband tightness on horses, quantifying the force being applied.
The research was published this week on the same day as a study that highlighted worrying numbers of horses competing in England, Ireland and Belgium with nosebands that were tighter than widely accepted guidelines.
The authors of the latest research, writing in the open-access peer-reviewed journal PLOS ONE, acknowledged that noseband tightness was difficult to assess in horses participating in equestrian sports.
“There is growing concern that nosebands are commonly tightened to such an extent as to restrict normal equine behaviour and possibly cause injury,” the researchers, based at Ireland’s University of Limerick, noted.
The study team, comprising Orla Doherty, Thomas Conway, Richard Conway, Gerard Murray and Vincent Casey, developed a simple model of what they called the equine nose-noseband interface environment which was used to develop a digital tightness gauge to reliably measure the normal force of noseband force on bridled horses.
Prevailing forces would understandably be highest at sites of high curvature, such as at the nasal bones, they said.
“The nasal plane area offers advantages over other sites for such measurements due to the clear anatomical landmarks available there and the simple and stable geometry of the site.” they said. Consequently, the probe design was optimised for this site.
They developed two prototype designs that went out for field trials, in which the pressure of the noseband was assessed across the top of the nose – the nasal plane – on 15 horses.
The results were then used to develop an ergonomically designed prototype, tested in a field trial involving 12 horses. In this trial, the noseband force was measured both on the nasal plane and on the side of the head − the lateral sub-noseband site.
Nosebands were set to three tightness settings in each trial as judged by a single rater using an International Society for Equitation Science taper gauge.
Forces in the range of 7 to 95 newtons (N) were recorded at the frontal nasal plane while a lower range of 1–28 N was found at the side site.
“The digital tightness gauge was found to be simple to use, reliable, and safe and its use did not agitate the animals in any discernable way,” they reported.
The authors said the force ranges measured at the frontal nasal plane were similar in both trials and corresponded well to the ISES taper gauge results. The range of force measurements as measured by the digital gauge corresponded to dead-weight loads of 1–9 kilograms.
The study team proposed a simple six-point tightness scale to aid enforcement of regulations, using normal force measurements, which they described as an objective discriminant.
Discussing their findings, the study team acknowledged that pain in horses was difficult to measure.
They noted that, in a study in cattle to measure the effects of force on tissue, the device used to apply the force was programmed to cut out at a force value of 20 N to prevent injury.
“It is clear from the forces measured here that noseband forces arising at localised sites on a horse’s head can be significantly larger than this cut-off threshold,” they said.
The large forces found where the noseband was tight enough to accommodate only half a finger may explain the reduced chewing, swallowing and yawning in horses with tight nosebands since mouth opening would involve additional mechanical action against the noseband, which would add force, they noted.
“Such movements have been found to produce very large peak forces in nosebands at standard recommended tightness levels.
“It would be interesting to have dynamic data for tight nosebands … to establish whether the use of such restrictive settings inhibit activities that could produce such transient [forces].
“Generally, there is a need to investigate the pain implications of both sustained and transient contact forces on animal tissue, in particular, and animal behaviour, in general, in order to provide meaningful guidelines.”
Casey and his colleagues noted that a wider noseband would result in a lower normal force per unit width − when the force is distributed over a larger area − and that some nosebands were not smooth underneath, further complicating the picture.
“However, while wider nosebands may therefore reduce the risk of pain, it has been shown that blood vessel occlusion in humans occurs at lower tourniquet pressures for wide tourniquets. Therefore, the effects of wider nosebands on the local circulatory system has also to be taken into account when assessing the overall physiological impact of tight nosebands.”
The impact of large pressure gradients such as those likely to occur along the edge of tight nosebands on local nerves should also be considered, they said. These may be reduced by fitting foam or other cushioning materials between the noseband and the nose, but the actual implications of such modifications were difficult to establish based on current knowledge, they added.
The authors said the dimensions of the probe meant it could not be inserted in nosebands assessed as able accommodate only half a finger or less.
“However, since this tightness level is commonly used in competitions there is a significant gap in our knowledge relating to magnitude of the forces and pressures likely to arise for such settings.
“Lower profile probes specifically tailored to such tightly fitted nosebands could be produced if such tight nosebands are deemed acceptable based on available or emerging evidence.”
The researchers said current FEI guidelines stipulated that tack stewards should check each noseband for tightness at the cheek.
“However, noseband applied force at this location is not representative of peak forces at other locations beneath the noseband and so is likely to be of limited use in estimating such peak values.
“In addition, variation in jaw position can radically change the geometry and hence the force/pressure applied by the noseband at such sites.”
They concluded: “Successful implementation of this tightness gauge technology and its acceptance by regulatory authorities and equestrian sports bodies will be very much dependent on a productive collaborative effort between equitation scientists, veterinary researchers, and the authorities and associations with interests in equine welfare.
“Ultimately, the goal must be to develop a set of standards which are evidence based and informed by expert opinion and which are implementable and generally acceptable to the broad equitation community.”
Doherty, Thomas Conway, Richard Conway and Casey are with the University of Limerick and have filed a patent application in Ireland relating to the digital tightness gauge; Murray is the owner-director of Aaron Value Adding Services Ltd, a company that provides an electronic printed circuit board production and prototyping service. The company manufactured, validated and performed preliminary circuit tests on the digital tightness gauge printed circuit boards used in this project.
Doherty O, Conway T, Conway R, Murray G, Casey V (2017) An Objective Measure of Noseband Tightness and Its Measurement Using a Novel Digital Tightness Gauge. PLoS ONE 12(1): e0168996. doi:10.1371/journal.pone.0168996