A noseband is such a familiar piece of tack that it can be easy to stop thinking about what it is actually doing.
But how tightly a noseband is fitted matters.
Research led by PCA Horse Welfare Lead Dr Kate Fenner looked at what happened to horses as a crank noseband was progressively tightened, measuring not only visible behaviour but also heart rate, heart rate variability and eye temperature.
The results are a useful reminder that a quieter mouth does not necessarily mean a more comfortable or relaxed horse.
Four different noseband fittings
The 2016 study involved 12 horses wearing a double bridle and crank noseband. Each horse experienced four different noseband settings on separate occasions. Importantly, the researchers used a standardised taper gauge rather than relying on individual finger size.
| Noseband fitting | What the researchers found |
|---|---|
| Unfastened | There was no evidence of the physiological stress response seen with the tightest noseband. Some changes in oral behaviour still occurred, which the researchers noted may have been associated with the horses wearing two bits for the first time. |
| Two fingers of space | Heart rate, heart rate variability and eye temperature did not show the stress response seen with the tightest setting. Chewing was not significantly reduced from baseline. |
| One finger of space | The physiological measures did not show the same clear stress response as the tightest setting, but chewing was significantly reduced. This is interesting because restriction of normal behaviour was becoming apparent before the strongest physiological stress response appeared. |
| No space under the noseband | This produced the clearest result. Heart rate increased, heart rate variability decreased and eye temperature increased, all consistent with a physiological stress response. Chewing fell markedly, swallowing approximately halved, licking stopped and yawning was virtually absent. |
At the tightest setting, the horses were standing still throughout the test, so the changes in heart rate and eye temperature could not be explained by exercise. The researchers concluded that a noseband fitted with no space underneath imposed sufficient discomfort to provoke a stress response.
A quiet mouth isn’t necessarily a relaxed mouth
One of the most interesting aspects of the study was what happened to normal oral behaviours.
As noseband tightness increased, swallowing showed a stepwise decline. Chewing was significantly reduced when the noseband allowed only one finger of space and again when there was no space at all. At the tightest setting, licking was eliminated and yawning was virtually absent.
That matters because opening the mouth, moving the tongue, chewing, licking and swallowing aren’t simply unwanted movements for us to eliminate. They are behaviours the horse may be motivated to perform.
Restricting the movement doesn’t necessarily remove the reason the horse wanted to make that movement in the first place.
What is ‘post-inhibitory rebound’?
This was perhaps the most fascinating part of the research.
Post-inhibitory rebound describes what happens when an animal is prevented or restricted from performing a behaviour and, when the restriction is removed, performs that behaviour more frequently than it did beforehand.
In other words, if licking normally happens at a certain rate, is restricted for a period, and then occurs at a much higher rate once the restriction disappears, that rebound tells us something.
The motivation to perform the behaviour didn’t disappear while it was being prevented. It appears to have built up.
In welfare science, that can be important because a post-inhibitory rebound may indicate that preventing the behaviour created a state of deprivation for the animal.
That is what researchers saw after the bridle and noseband were removed.
Yawning, licking and swallowing increased substantially during the recovery period. The researchers interpreted this as post-inhibitory rebound, suggesting the horses had become increasingly motivated to perform behaviours they had been unable, or less able, to perform while the equipment was on.
The yawning results are particularly striking. Yawning was virtually absent while the horses were wearing the equipment, then rose above baseline once it was removed. The authors suggested this could be associated with a reduction in arousal, conflict or anxiety once the equipment came off.
The tighter the noseband, the clearer the effect
The study doesn’t tell us that every behaviour a horse performs with its mouth means the noseband is uncomfortable. Nor does it mean every horse will respond identically.
What it does show is a pattern.
With two fingers of space, the researchers did not find the clear physiological stress response seen at the tightest setting.
At one finger, significant restriction of chewing was already evident.
With no space beneath the noseband, both behavioural restriction and physiological evidence of stress were present. Heart rate rose, heart rate variability fell and eye temperature increased. The researchers concluded that horses experienced pain or discomfort when the noseband was tightened to the point that there was no space underneath it.
That distinction is worth thinking about. We don’t need to wait until equipment produces an obvious wound or injury before considering its welfare impact.
What about the study’s limitations?
As with any research, context matters.
This was a controlled study involving 12 horses. The horses had not previously worn a crank noseband or double bridle, so they were responding to two bits as well as the changing noseband tightness. The researchers deliberately chose horses that were naïve to that equipment so that previous habituation would not mask their responses.
The horses were also standing still. There was no rider and no rein tension.
The authors therefore called for further research into horses accustomed to this equipment, the effects of single bits and rein tension, and longer-term exposure to restrictive nosebands.
Those limitations are important, but they don’t negate the central finding: when the noseband was tightened so there was no space underneath it, the horses showed measurable physiological stress and substantial restriction of normal oral behaviour.
What does this mean at Pony Club?
Pony Club Australia’s current National Gear Rules are straightforward.
Nosebands are not compulsory in any Pony Club discipline. If one is used, it must be comfortable for the horse and must not restrict breathing. PCA recommends checking fit with a taper gauge, or otherwise at the front of the nasal bones, and specifies two fingers of spacing.
A taper gauge is particularly useful because “two fingers” can mean very different things depending on whose fingers are doing the checking.
And perhaps the bigger lesson isn’t simply about passing gear check.
When fitting any piece of equipment, ask what it is doing to the horse.
If tightening a noseband makes chewing, licking, swallowing or other signs of oral discomfort disappear, that doesn’t necessarily mean we have solved the problem.
Sometimes we have simply removed the horse’s ability to show us.
Research
Fenner K, Yoon S, White P, Starling M, McGreevy P (2016), The Effect of Noseband Tightening on Horses’ Behavior, Eye Temperature, and Cardiac Responses, PLOS ONE 11(5): e0154179.
