What does a bit do to a horse and rider?


Dr Bob Cook has a research interest in the horse’s ear, nose and throat that goes back 60 years. However, it was not until 1998 that he started asking himself how the use of a bit affected the horse and rider. Now, two decades later, the professor emeritus of veterinary surgery with the Cummings School of Veterinary Medicine at Tufts University in Massachusetts explains where the research has led him.


Horses are born to reject anything in their mouth other than food or water. Accordingly, they are inherently averse to the bit. ‘Acceptance of the bit’ is an unrealistic expectation. A bit interferes with a sense organ (the mouth) and three body systems; the nervous, respiratory and musculoskeletal systems. Bit usage increases the risk of accidents and runs counter to the objectives of recreational riding (pleasure) and competitive riding (performance). A bit compromises horse welfare and human safety. Horse behavior improves when the bit is removed. The word ‘bit’ derives from bite, which also gives us the words bitter and beetle (‘the little biter’). Bits bite horses. A horse’s blameless aversion to a bit can lead to its rider developing an acquired aversion to their horse and even to the whole of riding.


“You can’t expect to wake up one morning and run a marathon without training. Similarly, asking good questions is a skill that requires practice, training, and mentoring.” — Ronald Vale¹


Though I have had a research interest in the horse’s ear, nose and throat since 1958, 40 years rolled by before it dawned on me – in 1998 – to ask the question in the title. It has taken me another 20 years to start answering the question with some first-of-a-kind data.

Why, in the 21st century, do humans ride horses?

In technologically advanced countries, the majority ride for pleasure. A minority ride to compete.

Is it correct to say that to ride or not to ride is largely a matter of choice?

Yes, apart for those in countries where the horse remains a necessity for transport and traction. For only a relatively small percentage of riders is it an occupation by which riders earn a living. Racehorse jockeys are professionals, not amateurs. Similarly, there are professionals in the worlds of dressage, show jumping, and other fields for whom riding and driving is a business.

When and why were bits first used?

Horses were probably ridden without bits long before mouthpieces of leather, wood and horn were introduced. In the Bronze Age, bronze bits would have prevented the horse from biting through the mouthpiece. Indestructible bits were probably viewed as an advantage at a time when horses were weapons of war.

Do bits control horses?

No. The data indicates that the bit is a common cause of loss of control, perhaps the most common.2,3

File image. © Mike Bain

What does a bit do to a horse?

It does many things but none are good for the horse. Most obviously it frightens and causes pain. Metal in a horse’s mouth messes with its mind. Removal of the bit in 66 horses reduced the total number of pain-induced behaviors in the study population from 1575 when bitted, to 208 when bit-free; a reduction of 87%.2,3 Some of the 69 bit-induced pain behaviors identified (e.g., rearing, bucking, stumbling and bolting) cause fatalities. A bit triggers ‘eating’ reflexes, whereas riding requires ‘running’ reflexes (Fig.1). The two sets of reflexes are diametrically opposed in function and mutually exclusive. We instinctively choose not to eat-and-run concurrently. The horse at liberty does the same. A bit handicaps the horse as an athlete.

What does a bit do to a rider?

Apart from enabling a rider to compete in those equestrian events for which a bit is mandatory, a bit does nothing for a rider. Bits do many things to a rider and, again, none of them are good. A horse in pain can be nervous, spooky, and slow to learn. Such a horse is no pleasure to ride and the risk of riding is increased. Pain penalizes performance so, for competition purposes, a bit is similarly counter-productive.

The questionnaire for the above study of 69 ‘bad’ behaviors in the horse 2, included an additional 10 questions about negative emotional states in the rider, e.g., anxiety/frustration at apparent inability to master the skills of riding; riding no longer pleasurable; reluctance to ride; fear of riding; personal injury; thoughts about retiring a horse that apparently had incurable problems; and an inclination to give up riding altogether. The 10 questions were answered twice by 45 riders. The total number of negative emotions was reduced from 200 when bitted to 18 when bit-free; a reduction of 91% (Cook 2018, unpublished material).

Apart from causing pain, does the bit have any other negative effect on a horse?

Yes, it frequently impedes breathing. At liberty, a horse runs with its head outstretched, mouth closed and lips sealed. Bit pressure too easily enforces poll flexion. A bit also breaks the lip seal, allows air into the mouth, and dissipates what should be a partial vacuum during ridden work. The soft palate no longer clings to the root of the tongue as it should do during rapid breathing. The soft palate may even become partially unfastened (‘dorsally displaced’) from the voice box (the ‘larynx’ in Fig.1). An untethered soft palate gets sucked dorsally at each inspiration, constricting the airway (‘nasopharynx’),and making it hard to breathe.

The soft palate (‘SP’ in diagram) works like a railroad switch plate or‘points’ but more ingeniouslyas it provides for different directions of flow and different functions;‘Down’ for breathing and ‘Up’ for swallowing.Track A for regular breathing is the ‘through’ track, ‘mainline,’default position. Track B for swallowing is the divergent line, for drinking, for gulping down dry food (hay) and, crucially, for preparing to run.For the purpose of illustration, an air space (green) is shown in diagram A but there should not be any air in a horse’s mouth during ‘gale-force’ breathing.The soft palate should be held tight to the root of the tongue by the suction forcesin the mouth, generated by one vital swallow immediately prior to running. At liberty, horses evacuate air from the mouth as a necessary preliminary to running. Diagram B shows the normal ‘dorsal displacement of the soft palate’that occurs transiently during a swallow. When running, even partial dorsal displacement (caused by the bit) suffocates.
The soft palate (‘SP’) works like a railroad switch plate o r‘points’ but more ingeniously as it provides for different directions of flow and different functions; ‘Down’ for breathing and ‘Up’ for swallowing. Track A for regular breathing is the ‘through’ track, ‘mainline,’ default position. Track B for swallowing is the divergent line, for drinking, for gulping down dry food (hay) and, crucially, for preparing to run .For the purpose of illustration, an air space (green) is shown in diagram A but there should not be any air in a horse’s mouth during ‘gale-force’ breathing.The soft palate should be held tight to the root of the tongue by the suction forces in the mouth, generated by one vital swallow immediately prior to running. At liberty, horses evacuate air from the mouth as a necessary preliminary to running. Diagram B shows the normal ‘dorsal displacement of the soft palate’ that occurs transiently during a swallow. When running, even partial dorsal displacement (caused by the bit) suffocates.

Being a nose-breather (i.e., quite unable to mouth-breathe) maintenance of the soft palate/tongue seal is essential for a horse to be able to breathe properly when running. So too, as with human athletes, is the freedom of its head. Unimpeded movement of the head/neck ‘pendulum’ is crucial for both breathing and balancing. The ‘head bob’ is an energy-saving mechanism that economizes on the work of breathing and motion. It is vital for the prevention of premature fatigue and potentially fatal falls. The soft palate switch is under the control of the autonomic nervous system; sympathetic for running (flight mode) and parasympathetic for swallowing (eat mode). It could be said that the horse ‘thinks with its mouth’ – a closed mouth for running and an open mouth for grazing .When running, if the soft palate is any position other than the fully ‘down’ position, a horse will start to suffocate.

The evidence is consistent with the theory that, in racehorses especially, instability of the soft palate and asphyxia leads to pulmonary edema (waterlogging of the lung), ‘bleeding’ and sudden death.4,5,6 As in man, asphyxia and waterlogging of the lung in the horse probably causes severe chest pain and a frightening sense of drowning.6 Researchers concluded that bit-induced breathlessness, a negative-emotional-state caused by shortage of air (suffocation),is a welfare issue for the horse.7 As a result of breathlessness followed by fatigue and a cascade of sprains, dislocations, falls, fractures, and lung hemorrhage, racehorses can have regrettably short lives.

For goodness sake! Anything else?

Yes; bit-induced lameness. Behavioral signs of pain are expressed by abnormal body movements directed towards avoidance or mitigation of pain; a fundamental survival response manifested via the musculoskeletal system. Abnormal movements are displayed by the head, neck, back, tail or limb. Movements range from the subtle to the obvious; occurring singly or in multiples; faster and further (bucking, bolting) or slower and smaller (stiffening, freezing). Using the term lameness in its widest sense of ‘disabled,’ the abnormal movements are expressions of bit-lameness. Sixty-nine signs of bit-lameness have been identified to date but the evidence indicates there are many more yet to be confirmed.2,3

I had no idea the horse was so averse to the bit. Why is this?

In biology, “movement of an organism in response to contact with a solid” is a behavioral phenomenon called stereotaxis; from the Greek ‘stereo’ (solid) and ‘taxis’ (movement). Movement towards a solid object (to engulf or eat) is referred to as positive stereotaxis and movement away (to avoid) as negative stereotaxis. This phenomenon is exhibited by both one-celled organisms (e.g., amoeba) and multi-cellular animals (e.g., mammals). A horse’s reaction to the bit – an undisputed solid object – is an example of hard-wired negative stereotaxis. Presented with the question ‘is a bit food or foe?’ the horse instinctively answers ‘foe.’A horse can neither swallow the bit nor spit it out. He may succeed in defending himself from the bit to some extent, e.g., by grabbing it between his teeth or trapping it under his tongue (‘getting his tongue over the bit’).

In the wild, a horse uses its highly sensitive lips when feeding to filter-out everything but food and water. A bit breaches this sensory barrier. Bits are foreign bodies. Every horse is inherently averse to a bit from the day it is born. Some show their dislike more vigorously than others. Bit-induced behaviors are reflex responses of normal animals to abnormal environments, i.e., stereotypic behaviors. They are the ridden equivalent of stable-induced behaviors like crib-biting and weaving. The expectation that horses should ‘accept the bit’ is misconceived and irreconcilable with a horse’s inborn negative stereotaxis.2,3 Any assertion that a particular horse actually ‘likes the bit’ is wishful thinking and a failure to recognize the behavioral signs of bit rejection. Unbuckle the bit hanger and a horse will drop the bit from its mouth.

File image. © Mike Bain

Can a horse be ridden without a bit?

Yes – with greater safety for the rider and humanity for the horse. Enhanced equine welfare will be accompanied by improved performance. Horse/rider harmony happens when horses’and riders’ interests coincide.

Is there any evidence in support of using a bit?

No. Even if there was, no amount of supportive evidence would validate its use. Scientific theories are validated by their ability to withstand refutation, not by their support. The only reason for using a bit is that it is mandated by the rules for certain competitions. Such rules, when introduced, were not evidence-based. The bit was given a free pass and ‘grand-fathered’ in without scrutiny.

Would a resolution to justify bit usage be defeated in any fact-based debate?

Yes. Evidence shows that bit-usage is refutable on many levels – horse welfare, rider welfare, ethics and equitation. At root, the bit is refuted by the species itself – its inherent aversion to an oral foreign body.

A horse is a highly tuned sentient animal. Its mouth is not just the first section of the digestive tract but also a sense organ, like the ear, eye and nose. It serves the senses of touch (lips, tongue, mucosa and gums) and taste (tongue). The tissue making up the ‘bars’ of the mouth is entirely bone. Gum is ‘skin’ of bone and more sensitive than ‘skin’ of shin. We recognize that saddles should not press directly on bone yet a bit on the bars is a bit on bare-bone. Embedding a metal rod in the mouth’s sensory ‘cave’ is like using a sledgehammer to crack a nut. To ‘hammer’ a horse is overkill.

Riders underestimate to their cost a horse’s sensitivity to their signals. Bit usage is not ‘best practice.’ Only a master horseman, after years of experience, can use a bit with the extreme delicacy of touch needed to avoid causing pain and triggering an aversive reaction. A feather-light bitless touch on the hair-bearing skin of the horse’s face provides a signal that is quite sufficient and significantly safer. It is something that can be aspired to by a novice horseman without inflicting pain while learning.

Given the option of competing bitless, riders will find – all other things being equal – that bitless horses out-perform bitted horses. A preliminary study hinted at the possibilities.8 Removal of the bit in four horses improved rider scores in two back-to-back four-minute tests from an average of 37 for the group when bitted to 64 when bit-free a few minutes later, a group improvement of 75%. A videotape of the study is available online.

The word bit is derived from the word ‘bite’.9 The answer to the question “To bit or not to bit?” becomes self-evident if the obsolete ‘e’ is restored. Posing the question as “To bite or not to bite?” reminds us that many signs of bit pain (e.g., headshaking) are the same as those caused by biting flies. But the pain is magnified by its location within a sense organ. From the horse’s point of view,the two canons of a jointed snaffle may feel like two monster-sized biting flies (or beetles) that, at any moment, might ‘fire with both barrels.’


  1. Vale, R.D (2013): The value of asking questions. Molecular Biology of the Cell, 24, 680-682. doi: 1091/mbc.E12-09-0660
  2. Cook W.R. and Kibler, M. (2018): Behavioural assessment of pain in 66 horses, with and without a bit. Equine Veterinary Education. Open access (free) article available.
  3. Cook W.R. (2018): Seventy reasons for not using a bit. The Horse’s Hoof, July issue, pp 26-29.
  4. Cook, W.R (2013): Bitted mouths cause waterlogged and ‘bleeding’ lungs: Racehorses need management, not medication.
  5. Cook, W.R. (2014): A hypothetical etiological relationship between the horse’s bit, nasopharyngeal asphyxia and negative pressure pulmonary edema (bleeding). Equine Veterinary Education. 26, 381-389
  6. Cook, W.R. (2016): Bit-induced asphyxia in the racehorse as a cause of sudden death. Equine Veterinary Education. 28, 405-409
  7. Mellor, D.J and Beausoleil, N.J. (2017). Equine welfare during exercise: An evaluation of breathing, breathlessness and bridles. Animals 7, 41; doi:10.3390/ani7060041& (open access article)
  8. Cook, W.R. and Mills, D.S. (2009): Preliminary study of jointed snaffle vs. crossunder bitless bridle: Quantified comparison of behaviour in four horses. Equine Veterinary Journal. 41,827-830 doi: 10.2746/042516409X472150
  9. Partridge, E (1958): Origins: A short etymological dictionary of Modern English. The Macmillan Company, New York

This report was first published in The Horse’s Hoof.


3 thoughts on “What does a bit do to a horse and rider?

  • May 8, 2020 at 9:38 am

    There is indisputable proof that riding a horse in a bitted bridle causes pain & suffering to a horse.
    For many years I rode my horses in bitted bridles, oblivious to the fact of how much pain I was subjecting them to, with the mindset that I had more control & that I was safer riding with a bitted bridle.
    I have, now, many years later, converted to a Dr Cook’s bitless bridle & my horse is so much more responsive, calmer & a pleasure to ride, he literally breathes a sigh of relief when I take the bridle off now & a metal bit doesn’t bang against his teeth.
    I will not subject him to that pain again, that putting a bit in his mouth causes, I cringe when I see horses being ridden in bitted bridles & also when I’m in saddleries & I see the many types of bits still for sale, these stores should be promoting the sale of bitless bridles for the horse’s welfare.
    Myself & my horse thank you for such a wonderful product.

  • May 28, 2020 at 3:40 am

    There is such a thing as relative calm. I feel that a bit should be left in factory, and never used in the mouth of your equine friend. I do not ride, but can imagine the fright of my mouth being over exaggerated by the pullingof my lips and the roof of my mouth being so bruised by the bit.
    Some humans should be wearing them instead.!! The delicate animal who is so big and muscular, is ready to learn a better way of experiencing pleasure in the field and on trails, and relax while learning, so you can love him/ her better and really want to vocoder one while on an outing. I wish I knew how to ride better, even at my age of 74 years, and only one lesson about 46 years ago!!
    It would be my wish come true to actually be present during a foaling of which I have seen on the television……..it was all I could do to be so involved while sitting on my couch. Thanks for this information!!…..and get rid of crops also!! ❤️❤️❤️❤️❤️

  • August 20, 2020 at 12:55 pm

    I was asking myself about bits and the plus and minus of them and all my questions were answered here.. I am new the horse world at the age of 58. I am hoping to become a horse owner in the next year. I don’t plan to ride but to give lots of love, trust and make the horse’s life the best it’s ever had. Thank you so much for the information.


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