The first study to confirm stress responses when horses are prevented from moving their jaws has brought the spotlight on increasingly popular nosebands, with estimates that one in two horses competing in dressage, show-jumping and eventing cannot open their mouths because of tight-fitting nosebands.
Tight nosebands can mask unacceptably rough riding.
A serious animal welfare issue for horses in equestrian events has been highlighted by new research from the University of Sydney’s Faculty of Veterinary Science.
This is the first study to show physiological stress responses when horses are prevented from moving their jaws.
The use of restrictive nosebands to bind together the jaws of sport horses is increasingly popular, with some estimates suggesting that half of the horses competing in dressage, show-jumping and eventing cannot open their mouths at all.
The study’s senior author, Professor Paul McGreevy, said the research shows how restrictive nosebands compromise natural behaviours and trigger a significant stress response in horses, which may violate the International Equestrian Federation’s (FEI) rule that nosebands are ‘never as tightly fixed so as to harm the horse’.
“In light of the current results, horse sport administrators may need to decide which oral behaviours they can afford to see eliminated in the name of sport,” he said.
“Tight nosebands can mask unacceptably rough riding. While wearing a bitted bridle, horses are highly motivated to open their mouths to find comfort but in dressage competitions, this response attracts penalties.”
To avoid such penalties, many riders now crank the jaws together with a system of leather pulleys (a crank noseband). This device is permitted under noseband rules, written before cranking was conceived, even though it increases pain and discomfort from the bits. This increase in aversive pressure boosts the rider’s control of the horse, which is why such nosebands appeal not only to dressage riders but also to many show-jumpers and eventers.
Pressure from nosebands has been likened to pressure from a tourniquet and often exceeds levels associated in humans with tissue and nerve damage. Crank nosebands are padded to avoid cutting into the surface of the skin, but inside the mouth, they force the cheeks against naturally sharp molars and are associated with lacerations and ulcers.
“The horse’s challenge when managing discomfort from a single bit is magnified if it is required to accommodate two bits, as is common at the elite level in dressage,” said Professor McGreevy.
“For example, every dressage horse at Olympic level must compete with a double bridle which means there are two metal bits in its mouth, one of which is a lever that tightens a metal chain under the chin. The incentive for riders to bind these horses’ jaws together to prevent displays of resistance increases accordingly.”
The team from the University of Sydney has been studying the effects of noseband tightening on horses’ behaviour, cardiac responses and eye temperature (a proxy for physiological stress).
In a paper published recently in PLOS ONE, the team reports that tight nosebands profoundly reduce yawning, licking, chewing and, perhaps worst of all, swallowing in horses wearing a double bridle.
The unique study is also the first to show that when the nosebands are removed and yawning, chewing, licking and swallowing are no longer prevented, horses show more of these behaviours.
”This so-called post-inhibitory rebound reveals the fundamental importance of these oral comfort behaviours,” Professor McGreevy said.
Many manuals and older rulebooks propose two fingers be used as a spacer to guard against over-tightening but some fail to specify where these should be placed or the size of the fingers.
In light of the prevalence of noseband tightening, the International Society for Equitation Science has called for a limit on noseband tightening and for the routine use of a standardised taper gauge, proposing this would be good for horse welfare and the sustainability of the sports themselves.