The term “bit blindness”, coined in 2020, emphasises that after its inception four millennia ago, bit use in horses has long been normalised [1,2]. Moreover, not only has the use of bits been normalised, so too were the distinctive behaviours associated with that use. Indeed, this dual normalisation was so widely accepted that when published evidence increasingly showed bit-induced mouth pain was the cause of clearly identifiable behaviours within the normalised spectrum [e.g., 3-11], it shocked equestrians who believed it [12].

Others simply did not want to accept that their routine use of bits could cause pain, so this possibility was ignored, claimed to be inconclusive, denied or denigrated. Such diversionary tactics have continued, and even intensified [13], probably in response to a progressive increase in the weight of physical evidence that bits can injure oral tissues and therefore cause pain [e.g., 1,14-25].

A particularly compelling account provides unequivocal evidence that bit use can, and often does cause pain [1]. It takes the form of a comprehensive evaluation of the following: pain receptor activation and brain-based pain experience; oral physiology, neurophysiology and the pathophysiology of oral injuries; the pain generated by compression, laceration, inflammation, impeded blood flow, and the stretching of tissues; and behavioural responses of horses to oral pain [1].

The assessment of these behavioural responses was based on the following comparisons [1]:

• horses routinely ridden or driven while fitted with bitted bridles compared to others with pain-free bit-free bridles;
• horses before and after transitioning from bitted to pain-free bit-free bridles;
• routinely bit-managed horses when not fitted with bridles or while only wearing a halter; and finally;
• all of the above compared with wild free-roaming horses [1,10,21,25,26,27] (See Table 1).

Table 1. Some behavioural indices of bit-related mouth pain in horses (reproduced with permission from [1])

1. Indicative pain-related behaviours in ridden bitted horses

Mouth: resists bridling; fussing with the bit, persistent jaw movements, chewing; crossing the jaw; slightly open or gaping mouth; teeth grinding, holding the bit between the teeth; tongue persistently moving or protruding from the mouth, tongue placed above the bit or retracted behind it; excessive salivation or drooling.

Head-neck: sudden evasive movements due to abrupt increases in rein tension; side-to-side shaking or up- down head tossing; jawline above horizontal; head tilted, stiff necked; rein-induced low jowl-angle, neck arched, nasal plane at or behind the vertical; reaches forward so rider uses longer rein.

Pain face: identifiable nostril flare, lip positions, ear positions, upper eyelid tension with white showing, and facial muscle tension.

Body movement/gait: stiff or choppy stride, hair trigger responses (hyperreactivity), crabbing; difficult to control, hesitant to move forward, difficult to stop, side-stepping from straight-line motion; bucking; rearing; tail swishing.

For sources, search for YouTube archive videos. See also this image folder which contains over 200 high resolution images documenting mouth pain in elite dressage horses.

Elite dressage horse showing indices of bit-induced pain. Image by Crispin Parelius Johannessen.

2. Bitted to bit-free changes in ridden horse behaviour

Mouth: all bit-related mouth behaviours absent; quiet, closed mouth, tongue inside mouth and appropriately placed; little or no teeth grinding; no drooling.

Head-neck: head tossing and other abrupt movements absent; lower head-neck position and wider jowl angle; head, neck and spinal column properly aligned longitudinally.

Pain face: no indications of mouth-related pain in healthy animals.

Body movement/gait: calm, relaxed and cooperative demeanour; engaged, lively, energised and exhibits vitality of fitness; head freedom supports balanced, aligned and smooth rhythm of motion; tail movement in synchrony with spinal movement.

For sources, search for YouTube archive videos.

3. Behaviours of bit-free horses at rest or when running free

As expected, domesticated horses wearing comfortably-fitted bit-free bridles do not display any of the bit-related behaviours noted above while standing at rest or engaging in exercise ranging from walking to galloping; nor do horses wearing halters while standing in stalls or moving freely during exercise or in turnout paddocks. Likewise, neither do wild, free-roaming horses when standing alert or when walking, trotting, cantering and galloping during roundups.

For sources, search for YouTube archive videos of bit-free domesticated horses, and of ~150 free-roaming, wild Brumbies (Australia), Camargue horses (France), Kaimanawa horses (New Zealand) and Mustangs (USA.)

It is recommended that readers assess for themselves the behavioural evidence outlined in Table 1, and when in contact with horses draw their own conclusions. In addition to specific publications (listed in [1]), YouTube videos are a particularly rich resource. Filmed independently of the specific purposes to which they are put here, they provide objectively observable records of equine behaviour in a wide range of sports, recreational, working and free-ranging circumstances.

Image source Dreamstime.com.

Pain and musculoskeletal lameness

Musculoskeletal lameness has been characterised by identifying several behaviours from a list of 24 elements of the Ridden Horse Pain Ethogram as listed in Table 2 [28,29,30]. Although these behaviours are among those discussed above as normalised and attributable to bit-induced pain, the potential involvement of the bit in generating the behavioural signs of musculoskeletal lameness (Table 2) is given only cursory attention, not mentioned at all, or is apparently actively avoided.

Table 2. The 24 elements of the ridden horse pain checklist

1. Repeated changes of head position (up/down), not in rhythm with the trot.
2. Head tilted or tilting repeatedly.
3. Head in front of vertical (>30°) for ≥10 s.
4. Head behind vertical (>10°) for ≥10 s.
5. Head position changes regularly, tossed or twisted from side-to-side, corrected constantly.
6. Ears rotated back behind vertical or flat (both or one only).
7. Eye lids closed or half closed for 2–5 s
8. Sclera exposed repeatedly.
9. Intense stare (glazed expression, “zoned out”) for ≥5 s
10. Mouth opening ± shutting repeatedly with separation of teeth, for ≥10 s.
11. Tongue exposed, protruding or hanging out, and/or moving in and out repeatedly.
12. Bit pulled through the mouth on one side (left or right), repeatedly.
13. Tail clamped tightly to middle or held to one side.
14. Tail swishing large movements: repeatedly up and down/side to side/circular; repeatedly during transitions.
15. A rushed gait (frequency of trot steps >40/15 s); irregular rhythm in trot or canter; repeated changes of speed in trot or canter
16. Gait too slow (frequency of trot steps <35/15 s); passage-like trot.
17. Hind limbs do not follow tracks of forelimbs but repeatedly deviated to left or right; on 3 tracks in trot or canter.
18. Canter repeated leg changes in front and/or behind; repeated strike off wrong leg; disunited
19. Spontaneous changes in gait (e.g., breaks from canter to trot or trot to canter).
20. Stumbles or trips more than once; repeated bilateral hind limb toe drag.
21. Sudden change of direction, against rider direction; spooking.
22. Reluctance to move forwards (has to be kicked ± verbal encouragement), stops spontaneously.
23. Rearing (both forelimbs off the ground).
24. Bucking or kicking backwards (one or both hind limbs).

More than ‘bit blindness’

An educational video, entitled Horses and the Science of Harmony [30], produced by Dr. Dyson, reveals a reluctance to evaluate the potential for the bit to be the source of most behaviours regarded as pain-related indices of musculoskeletal lameness.

Beginning at 1:02:17 in the video is a section headed “The Six Key Pressure Points Caused by the Bridle” in which Dr. Murray evaluates potentially painful pressure points of a bridle head stall. She comments first on the head piece that lies over the poll, then progresses in stages to consider the browband and temporomandibular joint, the cheek pieces, and the noseband.

At 1:02:46 there is a fleeting view of a snaffle bit. In a striking omission no comment is made about the pressure points inside and outside of the horse’s mouth. The exquisitely sensitive tissues omitted include the gums, tongue, lips, bone and teeth. However, riders are simply encouraged to consult bridle-fitting experts to minimise bit ‘discomfort’, without cautioning that any bit causes pain.

Conspicuous by their absence… Where are the pressure points impacted by bits? Image sourced from “The Science of Harmony”, by Padma Video.

To omit this seventh, potentially most significant and well-established cause of pressure and pain cannot be excused merely as “bit blindness”. Nor would a quibble that the head stall and the bit are two separate pieces of equipment excuse it. Rather, on the face of it, this appears to be a purposeful tactic to divert attention away from the bit, a tactic included among the Seven Pillars of Deception to Delay Action on Horse Welfare, outlined recently [13].

It is widely accepted that bits contact many pressure points on extraordinarily sensitive tissues, and surprisingly, bit manufacturers fail to see the negative welfare implications. Image source: www.bomberbits.co.za

Bona fide scientific methodology dictates that any plausible alternative explanation of a novel conceptual construct should be evaluated rigorously before being discarded. In this case, the question is whether bit-induced mouth pain could contribute to, or account entirely for, the behavioural signs of what is described as musculoskeletal lameness.

To date, this possibility has not apparently been tested by Dr. Dyson and her colleagues.

Note: It is here accepted that the behaviours in question are caused by pain. What the Dyson team have not yet explicitly ruled out is that the bitted mouth is an alternative source of pain. This is despite the exceptionally strong evidence that when horses are managed bit-free or are living bit-free, most of these pain-related behaviours are absent (See Table 1 above), leading to a rather obvious conclusion. This could also explain the surprisingly high prevalence of so-called “lameness” when reported using these behavioural signs in bitted horses [28].

It would have been straightforward for the Dyson team to design studies to test these alternative explanations.

References

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