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Does use of a bit endanger the health and safety of horse and rider? – Professor Robert Cook July 2022

Does use of a bit endanger the health and safety of horse and rider?

Robert Cook[1]

July 2022


My answer to the question in the title is ‘yes.’ Bit pain teaches horses conflict behaviours and handicaps their ability to breathe. Horses are stressed and disabled, both physically and mentally by the bit.  The damage is cumulative, causing clinical signs consistent with breathlessness, suffocation and post-traumatic stress disorder. More likely than not, the bit is the cause of “bleeding” and sudden death in racehorses but this explanation cannot be tested until bit-free competition is allowed. Likewise, bit-free competition is expected to reveal that the bit is the cause of a number of other respiratory diseases currently classified as of unknown cause.

It is recommended that rules mandating use of the bit for equestrian sport be repealed. The recommendation is in accord with the physiology of the horse; the policy of minimizing risk for the rider and preventing avoidable suffering for the horse (Campbell 2013); and the principles Least Intrusive, Minimally Aversive (LIMA 2022), which emphasize the use of positive reinforcement.



The horse is a nose-breathing animal. In the wild it runs with a closed mouth, sealed lips, and a negative atmospheric pressure in the oral cavity. The suction locks the soft palate onto the root of an immobile tongue and keeps its throat airway open. A bit breaks the lip seal, admits air into the mouth, unlocks the soft palate and obstructs the throat airway (for diagrams, see Cook 2021).

A review of the literature on the horse-human relationship reveals many studies (Hausberger et al 2008). There has been a shortage of data but, with regard to bit usage, data is now available (e.g., Cook and Strasser 2003, Cook 2010, Hockenhull and Creighton 2012, Björnsdóttir et al 2014, Mata et al 2015, 2022, Tuomola et al 2020). A negative correlation has recently been recognized between a welfare score for the horse and accidents for the rider, together with a positive correlation between rider accidents and hyperreactive horse behaviour (Luke et al 2022). The 91% prevalence of owner-reported ridden behaviour problems in UK leisure horses was considered to be a significant rider safety and horse welfare concern (Hockenhull and Creighton 2012). Evaluating equine welfare at exercise, Mellor and Beausoleil (2017) wrote, “most horses exhibit clear behavioural evidence of aversion to a bit in their mouths, varying from the bit being a mild irritant to very painful. This in itself is a significant animal welfare issue that should be addressed.”

The purpose of the present article is to list six additional data-sets for answering the question in the title.

  1. Two unschooled 2-year-old horses in a 10-day period of foundational training performed “at least as well, if not better” without bits as two matched horses in snaffle bridles (Quick and Warren-Smith 2009)


  1. At the 2006 Certified Horsemanship Association’s Annual Conference, a comparative trial took place (Cook and Mills 2009). In two identical and consecutive 4-minute dressage tests, first bitted then bit-free, four mature school-horses clearly demonstrated their preference for being ridden bit-free. In transitioning these horses for the first time from bit to bit-free and doing this sequentially with no more delay than it took to change the bridle, four riders – only one of whom had previously ridden bit-free – improved their independently judged dressage scores from a collective average of 37% when bitted to 64% when bit-free


  1. In a questionnaire-based study of 69 conflict behaviors, 66 leisure-horse riders documented the changes in their horse’s behavior when transitioned from bit to bit-free riding (Cook and Kibler 2019). The total number of conflict behaviors in the self-selected population when bitted was 1575, an average of 24 per horse. After a mean period of 35 days bit-free, conflict behaviors were reduced to 208, an average of 3 per horse; an 87% improvement. The prevalence of each of 69 behaviors, with and without the bit, was tabulated in order of frequency. The term ‘bit lameness’ was proposed to describe a syndrome of lameness caused by the bit. Bit pain had a negative effect on proprioception, i.e., on balance, posture, coordination and movement. Only one horse showed no reduction in pain signals when bit-free. The welfare of 65 of 66 horses was enhanced by removing the bit; reducing negative emotions (pain) and increasing positive emotions (pleasure). None of the riders experienced loss of control when bit-free; quite the opposite. Grading welfare on the Five Domains Model (Mellor et al 2020), it was judged that – when bitted – the population exhibited “marked to severe welfare compromise and no enhancement” and – when bit-free – “low welfare compromise and mid-level enhancement.” Exemplifying the criteria proposed by Campbell (2013) for distinguishing use from abuse, removal of the bit in 65 horses minimized risk for the rider and prevented avoidable suffering for the horse. In sum, 65 out of 66 horses benefitted from removal of an oral foreign body.


  1. From the same population, 45 of the riders answered 10 questions based on how their own feelings changed when riding bit-free (Cook and Kibler 2022). The total number of their negative feelings when bitted was 200 and when bit-free 18; a 91% improvement. The data indicated that rider’s feelings about riding were negatively influenced by their horse’s aversion to the bit. On the other hand, removing the bit significantly reduced the prevalence of bit-induced aberrant behaviour in their horse, increased their pleasure in riding, improved their riding skills and gave riders the chance to achieve that sense of harmony with their horse that is the goal of horsemanship.


  1. A study of stereotypic behaviour in a randomly selected population of 650 riding-school horses in Italy revealed a statistically significant difference between horses trained in the English and Western riding traditions (Normando et al 2002). From a total of 46 stereotypies, Western style horses comprised 9 out of 348 horses – a prevalence of 3%; whereas English style horses comprised 37 out of 302 horses – a prevalence of 12%. As the authors noted, English style “employs more hand to bit contact.”


  1. A survey conducted by the World Bitless Association revealed that, from 1636 participants, 9 out of 10 equestrians thought that bit-free competition should be allowed and, again, 9 out of 10 believed that by this means welfare would be improved.

Seven pointers can be derived from these studies when viewed in conjunction with independent animal welfare research …

  1. Use of the bit is a welfare issue for horse and rider (Cook and Strasser 2003, Mellor 2012, 2020, Hockenhull and Creighton 2012, Beausoleil and Mellor 2015, Mellor and Beausoleil 2017, Mellor and Burns 2020, Mellor et al 2020).
  2. Bit pain teaches horses a legion of ways to defend themselves from the bit (Cook and Kibler 2019, Mellor 2020).
  3. Following removal of the bit, avoidance behaviors markedly diminish over time, starting on day one of being bit-free (Cook and Kibler 2019).
  4. Bit-free riding is both possible and preferable (Cook 1999, 2021).
  5. Pain-free riding promotes “positive affective states” for the horse, i.e., an optimistic attitude to work (enthusiastic, cooperative) as opposed to pessimistic (anxious, fearful, spooky, resistant, distressed, depressed, helpless, or aggressive) and equivalent improvements for the rider (Mellor et al 2020; Mellor and Burns 2020, Cook and Kibler 2022).
  6. It is probably no coincidence that so many stereotypic behaviours are oral-based, e.g., crib-biting, wind-sucking, wood-chewing, and self-mutilation. We will learn more about the cause of these and other serious problems when bits become bygones.
  7. The data supports a hypothesis for further testing, i.e., that the bit is a cause of many unwanted behaviors, diseases, accidents and injuries in equestrian sport and that rules mandating its use should be repealed.

As a horse cannot expel the bit, attempts to evade it escalate the negative consequences of bit usage (e.g., Mellor and Beausoleil, 2017, Mellor 2020). Apart from pain, these consequences include breathlessness, suffocation, premature exhaustion and the high-risk behaviors of fear, i.e., the classical fight, flight and freeze responses. These are expressed as unsealed lips, gaping mouth, excessive salivation, abnormal head/neck posture, excessive sweating and behaviors with all-too-familiar stable names such as resists-bridling, sore mouth, rooting, pulling, leaning, muzzle-rubbing, tail-flashing, ear-pinning, hyper-flexing, headshaking, head tilting, lugging, bolting, bucking, rearing, refusing (i.e., freezing), shying, bleeding, stumbling and falling. Publications refer to its consequences; catastrophic dislocations, fractures and sudden death (Cook 2014, 2015, 2022, Cook and Kibler 2019, 2022, Mellor 2020).


A horse does not sense its external world by means of sensors in its mouth but by its senses of touch, balance, sight, sound and smell. By placing our messaging device in the mouth, we are signaling the wrong set of sensors. Instead, we should be signaling the horse’s senses of touch and balance. The horse’s skin is a sense organ of exquisite sensitivity, as witnessed by its response to the touch of a fly.

Use of the bit is a pathophysiological intervention of a sensitive body cavity, causing pain and handicapping an exercising horse’s ability to breathe (Cook 1999, 2015, 2021, Mellor and Beausoleil 2017). It is carried out in the absence of anesthesia and lasts on each occasion for periods varying from minutes to hours. The intervention is repeated on a semi-daily basis throughout a horse’s working life; retirement often being determined by poor performance and an accumulation of conflict behaviors. Users of this traditional method of training range in skill from ‘novice’ to ‘experienced.’

Developed in the Bronze Age, the implicit modus operandi of the metal bit method, apparent in any bit’s design, is that it is pain-based. Anyone who disputes this has not tried the Mellor pen test on themselves (Mellor 2020). Currently, learning theory is cited as the process whereby a ridden horse is thought to learn through ‘pressure and release’ (negative reinforcement). However, from the horse’s point of view, mouth ‘pressure’ is indistinguishable from pain and any ‘release’ is fleeting before the pain recurs. Hence avoidance strategies range from the counter-productive to the catastrophic.

Stereotaxis is a word derived from the Greek stereo: ‘hard, solid’. This fundamental property of even primitive life forms, also known as thigmotaxis, is defined as “the positive (or negative) response of a freely moving organism to cling to (or avoid) a solid object” (Mason 2006). Indisputably, a bit is a solid object. A horse is innately programmed to try and move away from (evade) the bit, i.e., to display negative stereotaxis. A definition for thigmotaxis (Greek: thigmo: touch’) emphasizes the point; “the motion or orientation of an organism in response to a touch stimulus”. When the touch is painful, stereotaxic stimuli are stronger. It follows that the equitation mantra requiring a horse to ‘accept the bit’ is misconceived. Expecting a horse to accept an oral foreign body is a biologically unrealistic expectation. All 69 conflict behaviors, including the syndrome of ‘bit lameness’, can be legitimately classified as stereotypic behaviours (Cook and Kibler, 2019). Mason (2006) proposed a definition of stereotypical behaviour based on three causal mechanisms, i.e., “repetitive behaviours induced by frustration, repeated attempts to cope and/or CNS dysfunction”. The reversibility of 69 behaviours in 65 of the bitted horses indicated that ‘CNS dysfunction’ was not their cause but ‘frustration’ and ‘attempts to cope’ were mechanisms consistent with the data. In Mason’s words again, stereotypical behaviours are generally “responses of normal animals to abnormal environments..” In captive animals, they stem from “a deficit in housing or husbandry, where a deficit means something that the animal would change if it could (e.g., a motivational deficit linked with frustration; a health deficit linked with nausea or pain; or a safety deficit causing fear).”  

The signs of bit-induced pain are common and obvious yet, for this very reason, are often mistaken for normal and therefore overlooked. Signs of bit-induced breathlessness range from premature fatigue and poor performance to sudden death. With regard to falls where dislocations and fractures have occurred, these may – understandably – be categorized on a systems basis as being ‘musculoskeletal’ in nature, focusing attention on pre-existing fetlock damage or the track surface as possible primary problems. However, the fall in the first place could also be secondary to exhaustion, i.e., inadequate oxygenation, supporting its classification as a ‘respiratory’ system problem. Sadly, the mandatory autopsy examinations on sudden death provide no guidance as most are reported as of ‘unknown cause.’ Adding to the ‘bit-induced asphyxia’ explanation for sudden death (Cook 2014, 2016), I have recently drawn attention to the existence of a trigeminocardiac reflex in the horse; postulating that bit-induced pain could also trigger such a reflex and cause death from cardiac inhibition, i.e., a ‘heart attack’ explanation (Cook 2022). A factor common to all the explanations for sudden death is that the bit could be a primary cause. The following recommendation will test this hypothesis.


The evolutionary purpose of acute pain is to drive learning, i.e., for a sentient animal to ‘move away’ from an external source of pain. For example, if we touch something sharp or hot, we withdraw our hand immediately, reminding us – we hope – to not touch that item again. This is a survival-based and reflexive response to an aversive and possibly life-threatening stimulus. Similarly, a free-roaming horse on sighting a predator is motivated to ‘move away’ from the predator. However, when a domesticated horse is encumbered with a bit, it does not have the option of ‘moving away.’ The source of pain is strapped in its mouth; it’s internal.  Whatever strategy a horse tries is doomed to fail. Even the fear-induced strategies of bucking, rearing and bolting can be of no avail. What a horse does learn from bit usage is a seemingly endless number of ways to attempt avoidance of the bit. In other words, bit usage teaches the horse a repertoire of aberrant, unwanted, conflict behaviour.

As a method of human-to-horse communication, the bit method is misconceived. A bit does not teach a horse to ‘obey’; quite the opposite.  It leads to a rider’s or driver’s loss of control. I conclude that the bit method of communication is painful, contraindicated, counterproductive, and unsafe.

Whatever else a bit causes, such as lung haemorrhage (‘bleeding’), stumbling, falls and sudden death, pain alone is sufficient reason why rules mandating use of a bit should be repealed. Once riders are allowed to compete bit-free, the superior performance of the bit-free horse will be followed by the voluntary abandonment of bit-based accessories such as draw reins, side reins, running reins, balancing reins, martingales, gag bits, ring bits, restrictive nosebands, double bridles and tongue-ties. In horseracing, two bits and a tongue-tie are probable causes of catastrophic accidents, ‘bleeding,’ breakdowns and sudden death (Cook 2015, 2016, 2022).  

Bit-free trials for all equestrian disciplines are recommended for revealing the benefits of repealing mandated-bit rules and demonstrating that ‘bit-on-bone’ is no longer an acceptable ‘standard practice.’ As horses feel and respond to a fly on their skin, the pain-free touch of strap-on-skin is pressure enough for an effective rein cue. If racehorses were permitted to compete bit-free my expectations are that …

  • A racehorse is likely to perform better when bit-free than when bitted
  • Exercise riders and jockeys will find that bit-free horses are calmer, less likely to spook, more compliant and easier to control
  • The superior performance of the pain-free, fully oxygenated horse will soon be noticed by owners, trainers and racegoers
  • The use of bits and tongue-ties will start to decline
  • ‘Bleeding’, catastrophic accidents and fatalities will become less and less common
  • Bit-induced wastage from behavioral problems will be reduced and racehorses will retire in better physical health and mental state for training in other disciplines
  • The bit will be revealed as the cause of many common respiratory diseases currently classified as of unknown cause, e.g., soft palate instability, dorsal displacement of the soft palate, epiglottal entrapment, dynamic collapse of the larynx and trachea, ‘scabbard’ trachea, small airway disease, exercise-induced pulmonary haemorrhage[2], exercise-induced hypoxemia, and hypoxemia-induced recurrent laryngeal neuropathy (‘roaring’).
  • The public image of horseracing (and all equestrian sports) will be enhanced.


1.    Beausoleil, N.J; Mellor, D.J. (2015): Introducing breathlessness as a significant animal welfare issue. N Z Vet J. 2015 Jan;63(1):44-51. PMID: 25004795 DOI: 10.1080/00480169.2014.940410

2.    Björnsdóttir S; Frey R; Kristjansson T; Lundström T. (2014): Bit-related lesions in Icelandic competition horses. Acta Vet Scand. 56

  1. Campbell, M.L.H.(2013) When does use become abuse in equestrian sport? Equine Vet. Educ. 25, 489-492.
  2. Cook, W.R. (1999): Pathophysiology of Bit Control in the Horse. Journal Equine Veterinary Science 19:196-204
  3. Cook W. R. (2010): Damage by the bit to the equine interdental space and second lower premolar. Equine Vet Educ. (2011) 23:355–60.

doi: 10.1111/j.2042-3292.2010.00167.x

  1. Cook, W, R, (2014): A hypothetical, aetiological relationship between the horse’s bit, nasopharyngeal asphyxia and negative pressure pulmonary oedema. Equine Veterinary Education 26, 381-389

  1. Cook, W.R. (2016): Bit-induced asphyxia in the racehorse as a cause of sudden death. Equine Vet Educ. 28, 405-409.
  2. Cook, W.R. (2021): Pain-free horsemanship. Weltexpress, ISSN 1865-2727
  3. Cook, W.R. (2022): Sudden death in the racehorse.

  1. Cook, W, R, Strasser, H (2003): “Metal in the Mouth: the abusive effects of bitted bridles.” Sabine Kells, Qualicum Beach BC, Canada
  2. Cook, W.R; Mills, D.S.(2009): Preliminary study of jointed snaffle vs. crossunder bitless bridles: Quantified comparison of behaviour in four horses. Equine Vet. J. 41, 827- 830.  DOI: 2746/042516409×472150
  3. Cook W.R; Kibler, M. (2019): Behavioural assessment of pain in 66 horses, with and without a bit. Journal of Equine Veterinary Education 31, Issue10, 551-560

  1. Cook W.R; Kibler, M. (2022): The effect of bit-induced pain in the horse on the feelings of riders about riding. effect of bit-induced pain in the horse on the feelings of riders about riding (2022) – World Bitless Association
  2. Hausberger, M; Roche, H; Henry, S; and Visser, K (2008): A review of the human-horse relationship. Applied Behaviour Science, 109, 1-24.
  3. Hockenhull, J and Creighton, E (2012): The use of equipment and training practices and the prevalence of owner-reported ridden behaviour problems in UK leisure horses. Equine Vet J. ISSN 0425-1644 DOI: 10.1111/j.2042-3306.2012.00567
  4. LIMA (2022): International Association of Animal Behavior Consultants. org
  5. Luke, LL; McAdie, T; Smith, B.P; Warren-Smith, A.K (2022): New insights into ridden horse behaviour, horse welfare and horse-related safety. Animal Behaviour Science 246 (2022) 105539
  6. Mason, G.(2006): Stereotypic behaviour in captive animals: fundamentals and implications for welfare and beyond. Chapter 11. In: Stereotypic Animal Behavior; Fundamentals and Applications to Welfare, 2nd edn. Eds:  Mason and J. Rushen. CAB International, North America
  7. Mata F;Johnson C; Bishop C; (2015): A cross-sectional epidemiological study of prevalence and severity of bit-induced oral trauma in polo ponies and race horses. J Appl Anim Welf Sci, 18, 259-268
  8. Mellor, D.J. (2012): Animal emotions, behaviour and the promotion of positive welfare states. N Z Vet J, 2012 Jan;60(1):1-8. PMID: 22175422 DOI: 1080/00480169.2011.619047
  9. Mellor, D.J (2020): Mouth Pain in Horses: Physiological Foundations, Behavioural Indices, Welfare Implications, and a Suggested Solution. Mellor DJ. Animals (Basel). 2020 Mar 29;10(4):572. doi:10.3390/ani10040572
  10. Mellor, D.J; Beausoleil, N.J. (2017): Equine welfare during exercise: An evaluation of breathing, breathlessness and bridles. Animals, 7, 41
  11. Mellor, D.J; Burns, M. (2020): Using the Five Domains Model to develop welfare assessment guidelines for Thoroughbred horses in New Zealand. N. Z. Vet. J. 2020, 68, 150–156.
  12. Mellor, D,J; Beausoleil, N.J; Littlewood, K.E; McClean, A.N; McGreevy, P.D; Jones, B. A; and Wilkins, C. (2020): The 2020 Five Domains Model: Including Human–Animal Interactions in Assessments of Animal Welfare. Animals 2020, 10, 1870; doi: 10.3390/ani10101870
  13. Normando, S; Canali, E: Ferrante, V; Verga, M (2002): Behavioral problems in Italian saddle horses (2002): ScienceDirect

  1. Quick, J.S.and Warren-Smith, A.K. (2009): Preliminary investigations of horses’ (Equus caballus) indices to different bridles during foundation training.  Vet. Behav. 4, 169- 176.
  2. Tuomola, K; Mäki-Kihniä, N; Valros, A; Mykkänen, A; ,Kujala-Wirth, M (2020): Risk factors for bit-related lesions in Finnish trotting horses. Equine Veterinary Journal.
  3. World Bitless Association Survey (2020):

[1] Professor Emeritus of Surgery, Cummings School of Veterinary Medicine, Tufts University, USA

Email: bob.cook @

Postal address: 125, King Street, Cohasset, Massachusetts 02025 USA

[2]  Or, as I suggest it should be called, asphyxia or bit-induced pulmonary haemorrhage

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