BIT-INDUCED DISEASES AND BEHAVIORS IN THE HORSE
- Robert Cook
Professor Emeritus, Cummings School of Veterinary Medicine, Tufts University, USA.
Email: bob.cook@tufts.edu
INTRODUCTION
A rider’s or driver’s purpose in strapping a metal bit in a horse’s mouth is to provide control. With a rein attached to each end of the bit, manipulated from a distance, the assumption is that directional cues can be given, using the horse’s highly developed oral sense of touch. Unfortunately, the assumption is incorrect exactly because the mouth is so sensitive and the method so insensitive. It is like using a sledgehammer to crack a nut, a question of overkill, i.e., “the use of inordinate force (in this case force and pain) to achieve an objective.” The infliction of pain is not only unnecessary (and inhumane) but also accompanied by a plethora of side effects (unwanted conflict behaviors) that makes the method ineffective, as each one results in a loss of control. Apart from this, the bit method has another six physiological flaws:
- The horse evolved to reject all items in its mouth other than food or water. A bit is a painful foreign body. To expect a horse to ‘accept the bit‘ is an unrealistic expectation.
- The horse is a nose-breathing animal. As a prey animal, its first line of defense is to run. To breathe when running, a horse must seal its lips and, with a swallow before running, develop and maintain a negative atmospheric pressure in its oral cavity. Otherwise, its soft palate elevates at each intake of air and narrows the throat airway, i.e., strangles and suffocates. This, in turn, causes waterlogging of the lung, negative pressure pulmonary edema (‘bleeding’), premature exhaustion, falls, fractures, catastrophic accidents and sudden death.
- The leverage of bit pressure, applied at the tip of the head/neck ‘pendulum’, prevents the horse from extending its head and neck at the canter and gallop, hence another throttling effect.
- A bit causes a horse constant aggravation and pain, i.e., a negative affective mental state (Mellor et al 2020). The horse responds with one or more of 69 conflict behaviors (e.g., bolting, bucking, rearing, head tossing) aimed at trying to nullify the annoyance. A horse will tend to prioritize these responses over complying with the rider or driver’s directional and slowing cues. As a result, the bit is a common cause of loss of control.
- As rein tension draws the bit back in the mouth it will, by stretching the lips, cause lip pain, gum pain over any unerupted ‘wolf’ tooth, and dental pain by clashing with and eroding the first lower cheek tooth. The horse may solve this problem by grabbing the bit between its teeth. In so doing, the horse is now in charge and a rein cue is no longer available. In his narrative poem, “Venus and Adonis” Shakespeare (1593) describes the bit-grabbing behavior succinctly …
“The iron bit he crusheth‘tween his teeth,
Controlling what he was controlled with.”
- Like all mammals, the horse has a trigeminocardiac reflex, a ‘face/heart’ connection. Bit-induced bilateral stimulation of one or more branches of the trigeminal nerve (the sensory nerve to the head with its multiple connections to the vagal nerve that controls the action of the heart) could well be a cause of sudden death at exercise due to vagal inhibition of the heart and cardiac arrest, i.e., a ‘heart attack.’ (Chowdhury and Schaller 2015, Cook 2024a).
In short, the bit does not always control. The myth that it controls without causing serious side-effects is misleading and incorrect. For welfare and safety reasons, a bit-free option is recommended for all equestrian sports.
Two checklists in this article, one on bit-induced diseases and one on bit-induced behaviors, support the World Bitless Association’s rule-change request, on welfare grounds, to allow bit-free bridles in all FEI-sponsored horse sports. Included in the first list are diseases that are more typical of racing, but as most of these also occur in FEI (Fédération Equestre Internationale) sports, albeit with less frequency, they need to be considered. The article is, anyway, a recommendation for bit-free racing to be allowed and for freeing the horse from the bit in every equestrian discipline.
Graphic courtesy of Michelle Guillot
Part 1: BIT-INDUCED DISEASES
The free-roaming horse in the wild runs with a closed mouth, sealed lips, a negative pressure in the oral cavity, and an extended head/neck position.
A bit breaks the lip seal, dissipates the negative pressure, flexes the head and neck, and prevents a horse from breathing freely (Cook 1999). In the racehorse particularly, but not exclusively, bits cause:
Mouth pain (Mellor 2020).
A negative affective mental state (Mellor et al 2020).
Trigeminal neuralgia (one of the severest pains known to man).
Constriction of the throat airway when running.
Instability of the soft palate.
Breathlessness, strangulation, and suffocation.
Dorsal displacement of the soft palate (DDSP).
Epiglottal entrapment.
Dynamic collapse of the voice box (larynx) and windpipe.
Permanent constriction and deformity of the windpipe (‘scabbard’ trachea).
Negative pressure pulmonary edema (“bleeding”), a disease in man (and probably the horse) that causes intense chest pain, fear, and a sense of drowning.
Inflammatory airway disease as a sequel to repeated episodes of bit-induced bleeding.”
Exercise-induced hypoxemia (low oxygen levels in the blood).
Premature exhaustion and poor performance
Heaviness on the forehand.
Tendon and ligament sprains.
Stumbling.
Falls.
Fractures.
Catastrophic accidents.
Sudden death from negative pressure pulmonary edema and/or from a “heart attack” triggered by bit-induced stimulation of the overlooked trigeminocardiac reflex (Chowdhury and Schaller 2015, Cook 2022).
In all sports the bit can also cause:
Sore mouth and buccal ulcers.
Inappetence and reluctance to drink.
Bruising and excoriation of the lips.
Cyanosis of the tongue (‘blue tongue’).
Laceration of the tongue (Figure 1)
and, though rarely, amputation of the anterior section of the tongue.
Bone spurs on the bars of the mouth (Figures 2a 2b and 2c).
Fractures of the mandible.
Erosion of dental enamel (Figure 2a).
Paradontal disease and loss of teeth (Figure 2a).
Career-ending musculoskeletal diseases and wastage.
Figure 1. Laceration of the tongue.
Figure 2a. Bit-induced ‘wave mouth’ deformity of the molar arcades and severe erosion of the first two cheek teeth in the lower jaw. Note the proximity of the canine tooth root in the lower jaw to the foramen from which the mandibular nerve emerges and its proximity to the anterior section of the bars of the mouth. At the most posterior point of the so-called interdental space (bars of the mouth) an unerupted ‘wolf’ tooth may be present. (Specimen courtesy of the American Museum of Natural History)
Figure 2b. Three large bit-induced bone spurs on the right side of the bars and a smaller one on the left. A principle of saddle fitting is that at no place should the saddle press directly on bone; a principle that is disregarded in use of the bit. (Specimen courtesy of the American Museum of Natural History).
Figure 2c. Bone spurs on both bars, with the ones on the left side being more obvious because seen in profile
Additional illustrations of bit-induced damage are available at (Cook 2023b)
The trigeminocardiac reflex (TCR) is a potentially fatal reflex of mammals first described by Florian Kratschmer in 1869. He discovered by animal experiment that stimulation of the upper airway resulted in cardiac arrhythmias. Since then, three subtypes of this reflex have been recognized in man, each of which can cause a reduction of blood pressure, a slowing of the heart, and cardiac arrest. The Trigeminal nerve has three main branches, the ophthalmic, maxillary, and mandibular nerves (Figures 3 and 4). The three fatal reflexes are named accordingly, the oculocardiac, maxillocardiac and mandibulocardiac reflexes.
Figure 3. The three main branches of the Trigeminal nerve: the Ophthalmic nerve to the eye and skin of the forehead; the Maxillary nerve to the upper jaw; and the Mandibular nerve to the lower jaw. Note how the mandibular nerve emerges from the mental (‘chin’) foramen to innervate the bars of the mouth, the canine and incisor teeth, and why bit pressure triggers nerve pain (neuralgia). Note the unerupted ’wolf’ tooth in the lower jaw, just in front of the first cheek tooth. The bars of the mouth will be especially sensitive in a young Thoroughbred colt that is ‘teething.’ Canine teeth do not finish erupting until the colt is 6 years old. Mares commonly have unerupted canine teeth, the roots of which lie immediately under the bars. The crowns may cause a protrusion on the surface.
Figure 4. A cross-section of the lower jaw at a level between the mental foramen and the first cheek tooth. Though this jaw was from a horse of above average height, note how its size compares with that of a standard-sized chicken’s egg and how the bone comes to a peak under the ridge-like bars of the mouth. The ‘bars’ are not flat as the name implies and, therefore, bit pressure is intensely painful point pressure. The red beads represent the mandibular nerve.
Any surgery in man on tissues innervated by the Trigeminal nerve carries the risk of triggering a fatal consequence from vagal inhibition of the heart. The point at issue here is that use of the bit method of communication is invasive surgery in a sensitive body cavity, carried out daily, without anesthesia, using one or more blunt instruments on tissues supplied by the mandibular nerve. Stimulation of the trigeminocardiac reflex must be listed as a possible cause of sudden death in the racehorse.
Part 2: BIT-INDUCED BEHAVIORS
Bit-on-bone pressure causes intense and recurring pain. Horses develop dozens of ways to try and cope with the pain but, other than ejecting the rider or grabbing the bit, none are successful. The strategies are referred to as ‘conflict’ behaviors, but these are not immutable character faults, and the horse should not be blamed. In a questionnaire-based assessment of pain in 66 horses, with and without a bit (Cook and Kibler 2019) the most frequently expressed concern was “My horse hates the bit”; a concern closely followed by “lack of control.” Both concerns refute the myth that a bit controls a horse.
In decreasing order of frequency, the signs of pain were expressed by 69 behaviors as follows:
Hates the bit
Fright (nervous, ‘spooky’)
Stiff-necked
Lack of control
Resents bridling
Above the bit (high head carriage)
Muzzle rubbing
Head tossing (Trigeminal Neuralgia)
Unfocused
Flight
Fight
Pig-rooting
Difficult to steer
Stiff or choppy stride
Reluctant to rein back
Tail swishing
Hair trigger response to bit pressure
Sneezing and snorting
Yawning
Uncooperative and difficult to train (unfairly labelled as a ‘slow learner’)
Heavy on the forehand
Fails to stand still
Pulling on the bit
Grazing on the fly at exercise
Inverted frame
Dislikes wind/rain/sunlight
Tilts head at exercise
Fails to maintain trot or canter
Difficult to mount
Grabs the bit
Lacks courage
Napping
Stumbling
‘Freezing’
Resents unbridling
Behind the bit (overbending)
Head shyness
Salivates excessively
Bucking or bounding
Lazy or dull
Heads for the stable
Jigging
Unfriendly in the stable
Anxious eye
Ear pinning at exercise
Gaping mouth
Lolling tongue
Reluctant to change lead
Bites at the tack or other horses
Scuffs hind hooves
Backing-up
Multiple wrinkles around the muzzle
Crossing the jaw
Evades haltering in the paddock
Sweats excessively
Overbends
Tongue over bit
Interfering
Rearing
Runs wild on a bitted lunge rein
Lower lip slapping
Incoordination
Watery eyes
Exercise triggers coughing
Back problems
Retracts tongue behind the bit
Drops food from the mouth (quidding)
Reluctant to drink during endurance riding
For each of the 66 horses, the number of behavioral signs when bit-ridden and bit-free was tabulated, together with the percentage reduction of the sign when bit-free. For some years after the article’s publication (Cook and Kibler 2019) it was in the top percentile of articles downloaded in the peer-reviewed journal Equine Veterinary Education. This was an appropriate interest in that it was, and still is, the first and only data to be published on the effect of the bit on the ridden horse.
To summarize the results: A questionnaire study of 37 pain-based behaviors in 66 horses revealed that the total of such behaviors in the population when bit-ridden was 1575. The total when bit-free was 208, an 87% improvement. When bit-ridden, the median number of behavioral signs of pain per horse was 23. After being bit-free for a median period of 35 days, the median was 2.
An additional ten questions were answered by 45 of the 66 riders who reported how their own feelings about riding changed when they rode bit-free. Again, this is the first such data to be published (Cook and Kibler 2022).
To summarize these results: When using a bit, 45 riders reported a population total of 200 negative feelings about riding. When bit-free, they reported 18, a 91% improvement. The rider’s feelings were negatively affected by their horse’s feelings about being bit-ridden, namely their aversion to the bit.
An earlier study (Cook and Mills 2009) was carried out as a demonstration at the 2007 annual conference of the Certified Horsemanship’s annual conference. It tested the hypothesis that if a horse that had been ridden all its life in a snaffle bridle was first bit-ridden in a standardized test and then, immediately after, ridden again bit-free through the same test that there would be no change in its behavior. It was predicted that there would be change and that the horse’s behavior would improve when bit-free. Four mature school horses, none of which had ever been ridden in a crossunder bit-free bridle, were ridden through two 4-minute exercise tests, first bit-ridden then bit-free. An independent judge marked the 27 phases of each test on a 10-point scale. The four riders’ mean score when bit-ridden was 37%; and when bit-free 64%. The results refuted the hypothesis and upheld the prediction.
Since 2000, many thousands of recreational riders worldwide who previously rode with a bit have switched to bit-free riding. Significantly, no reports of accidents attributable to bit-free riding have been published. A global survey of 1636 bit-free riders revealed that 93% were in favor of bit-free competition being allowed across the disciplines (World Bitless Association 2020).
The data shows that the welfare and safety of horses and riders is improved by removing the painful, suffocating, frightening and potentially fatal bit. The request to the International Equestrian Federation (FEI) for a rule change to allow bit-free bridles in all FEI-sponsored horse sports is vindicated.
CONCLUSIONS
Since 2000, recreational riders in large numbers have shown by example that:
- Horses can be ridden without a bit …
- Without incurring any of the above diseases, …
- Or developing any of the above behaviors.
- Control is improved.
- Bit-free horses are calmer and more compliant.
- Riders feel more confident about riding and less stressed.
- Accidents have been noticeable by their absence.
For the last 10 years, the Royal Dutch Equestrian Federation has made virtual dressage available at all stages short of Grand Prix. Earlier this year, Pony Club Australia introduced a rule change that allowed their members, on application, to ride bit-free. Since then, many Pony Clubs all over the world have followed suit.
Assessment of equine welfare using the Five Domains Model (Mellor et al 2020)
requires that the negative affective mental state of a bit-ridden horse be acknowledged. The adoption of the Five Domains Model by the International Federation of Horseracing Authorities (IFHA) is an encouraging step in this direction. The IFHA is a foundation member with Fédération Equestre Internationale (FEI) of the International Horse Sports Confederation and is affiliated to the World Organisation for Animal Health (WOAH).
Graphic courtesy of Michelle Guillot
DOCUMENTATION
(Listed by year of publication, starting with 2024)
Mellor, D.J (2024b): Thoroughbred Horse Welfare Challenges: From Rape to Relegation. Horses and People Magazine.
https://horsesandpeople.com.au/thoroughbred…
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Cook (2024a): A bit-free, pain-free future for the free-breathing horse. https://worldbitlessassociation.org/resources/bit-free-pain-free-future-for-the-free-breathing-horse/
Cook (2024b): The evidence for allowing a bit-free option in equestrian sport. Horses and People Magazine
The Evidence for Allowing a Bit-Free Option in Equestrian Sport (horsesandpeople.com.au)
Cook (2024c): Horse Sports’ Option: Ban or be Banned. Horses and People Magazine. https://horsesandpeople.com.au/horse-sports-options-to-ban-or-be-banned/
Harvey, A. (2023). A Bit of a Problem in Equine Welfare: What is the Role of Veterinarians? Center for Veterinary Education, Control and Therapy Series, Number 6001. Issue 313, pp23-26. 8.
Cook, W.R. (2023a): Sustaining the social license for equestrian sport. [including the chronology of horse welfare development] Horses and People Magazine.
Cook, W.R. (2023b): Data and visual evidence for the bit-free debate.
Data and Visual evidence for the Bit-free debate – World Bitless Association
Luke K.L., McAdie T., Warren-Smith A.K., Smith B.P. (2023): Bit use and its relevance for rider safety, rider satisfaction and horse welfare in equestrian sport. Applied Animal Behaviour Science, Volume 259 February 2023, 105855
The Classical Riding School.com (2023): Going Bitless. Going Bitless: The Ultimate Guide to Transitioning to Bitless Riding. Theclassicalridingschool.com)
Wikipedia (2023): Horse Welfare.
Cook, W.R. (2022): Sudden death in the racehorse.
https://worldbitlessassociation.org/resources/sudden-death-in-the-racehorse/
Cook, W.R. and Kibler, M (2022): The effect of bit-induced pain in the horse on the feelings of riders about riding The effect of bit-induced pain in the horse on the feelings of riders about riding (2022) – World Bitless Association
Holmes, T.Q. Brown, A.F (2022): Champing at the Bit for Improvements: A Review of Equine Welfare in Equestrian Sports in the United Kingdom. doi: 10.3390/ani12091186.
Mellor, D.J., Beausoleil, N.J., Littlewood, K.E., McLean, A.N., McGreevy, P.D., Jones, B. and Wilkins, C. (2020). The 2020 Five Domains Model: Including Human–Animal Interactions in Assessments of Animal Welfare. Animals10(10), 1870; doi.10.3390/ani10101870
Mellor, D.J. (2020). Mouth pain in horses: Physiological foundations, behavioural indices, welfare implications and a suggested solution. Animals 10(4), 572; https://doi.org/10.3390/ani10040572
World Bitless Association (2020): The General Report of the 2020 WBA survey
https://worldbitlessassociation.org/resources/the-general-report-of-the-2020-wba-survey/
Cook, W. R. (2019): Clearing the Air on the Bit-free Debate. Horses and People Magazine, November-December issue
Mellor, D.J. (2019a): Equine welfare during exercise 1. Do we have a bit of a problem? https://www.slideshare.net/SAHorse/equine-welfare-during-exercise-do-we–have-a-bit-of-a-problem
Mellor, D.J. (2019b): Equine welfare during exercise 2. Do we have a bit of a problem?
https://www.youtube.com/watch?v=rY4yEC7lhco
Cook, W.R. (2019). Horsemanship’s ‘elephant-in-the-room’ – The bit as a cause of unsolved problems affecting both horse and rider.
Marsh,L., McGreevy,P., Hazel,S., Santos,L., Herbart,M.. Franklin,S. (2019). The effect of tongue tie application on stress responses in resting horses. BioRxiv 2019, 634717. Available online: https://www.biorxiv.org/content/10.1101/634717v1
Cook W.R. and Kibler, M. (2018): Behavioural assessment of pain in 66 horses, with and without a bit. Equine Veterinary Education. 31 551-560
(PDF) Behavioural assessment of pain in 66 horses, with and without a bit (researchgate.net)
Bellini et al (2018: Maxillomandibulocardiac reflex in a dog Acta Vet Scand
doi: 10.1186/s13028-018-0421-5
Chowdhury,T. and Schaller, B.J. (2015): Trigeminocardiac Reflex. Academic Press, London
Beausoleil, N.J. and Mellor, D.J. (2015). Introducing breathlessness as an animal welfare issue. New Zealand Veterinary Journal 63, 44-51
Mellor, D.J. (2016). Updating animal welfare thinking: Moving beyond the ‘Five Freedoms’ towards ‘A Life Worth Living’. Animals 6(3), 21; doi.org/10.3390/ani6030021
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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 https://doi:10.1111/eve.12196
Hockenhull, JS (2013): The use of equipment training practices and the prevalence of owner-reported ridden behavior problems in U.K. leisure horses. Equine Veterinary Journal, January
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Untangling the Complex Relationships between Horse Welfare, Rider Safety, and Rider Satisfaction. Anthrozoos, 721-736
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Cook, W.R. and Strasser, H (2003): Metal in the Mouth: The abusive effect of bitted bridles. Sabine Kells, Qualicum Beach, BC, Canada.
Cook, W.R. (2003): Bit-Induced Pain; a cause of fear, flight, fight and facial neuralgia in the horse. Pferdeheilkunde, 19, 1-8
Cook, W.R. (2000): A solution to respiratory and other problems caused by the bit. Pferdeheilkunde, 16, 333-351 http://www.bitlessbridle.com/Pferdeheilkunde_Solution.pdf
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