Equine welfare during exercise: Do we have a 'bit' of a problem? #horsewelfare

Equine welfare during exercise:
Do we have a ‘bit’ of a problem?
Professor Emeritus David J Mellor
BSc(Hons), PhD, HonAssocRCVS, ONZM
D.J.Mellor@massey.ac.nz
Foundation Director
Animal Welfare Science and Bioethics Centre

Key Published Sources
• Cook, W.R. (1999). Pathophysiology of bit control in the horse. Journal of Equine
Veterinary Science 19, 196–204.
• McGreevy, P.; McLean, A. (2005). Behavioral problems with the ridden horse. In
The Domestic Horse: The Origins, Development, and Management of Its Behavior;
Mills, D.S., McDonnell, S.M. Eds.; Cambridge University Press: Cambridge, UK;
pp. 196–211.
• Cook, W.R.; Mills, D.S. (2009). Preliminary study of jointed snaffle vs. crossunder
bitless bridles: Quantified comparison of behaviour in four horses. Equine
Veterinary Journal 41, 827–830.
• Quick, J.S.; Warren-Smith, A.K. (2009). Preliminary investigations of horses’
(Equus caballus) responses to different bridles during foundation training. Journal
of Veterinary Behaviour 4, 169–176.
• Van Lancker, S.; Van der Broeck, W.; Simoens, P. (2007). Incidence and
morphology of bone irregularities of the equine interdental space (bars of the
mouth). Equine Veterinary Education 19, 103–106.
• Cook, W.R. (2011). Damage by the bit to the equine interdental space and second
lower premolar. Equine Veterinary Journal 23, 355–360.

Key Published Sources
• 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 racehorses.
Journal of Applied Animal Welfare Science 18, 259–268.
• Doherty, O., Casey, V., McGreevy, P., Arkins, S., 2017a. Noseband use in equestrian
sports – An international study. PLoS One. 2017; 12(1): e0169060.
• Doherty O, Conway T, Conway R, Murray G, Casey V., 2017b. An objective
measure of noseband tightness and its measurement using a novel digital tightness
gauge. PLoS ONE 12(1): e0168996. https://doi.org/10.1371/journal.pone.0168996
• Mellor, D.J.; Beausoleil, N.J. (2017). Equine welfare during exercise: An evaluation
of breathing, breathlessness and bridles. Animals 7(6), 41; doi:10.3390/ani7060041 –
open access/free
• Cook, W.R.; Kibler, M. (2018). Behavioural assessment of pain in 66 horses, with
and without a bit. Equine Veterinary Education. doi.org/10.1111/eve.12916
• Uldahl, M.; Clayton, H.M. (2018). Lesions associated with the use of bits,
noesebands, spurs and whips in Danish competition horse. Equine Veterinary
Journal. doi.org/10.1111/evj.12827

Areas considered
• Hold your horses!
- Background to the use of bitted bridles
• Straight from the horses mouth
- Evidence for bit-induced pain: indicative behaviours and bone pathology
• Bit-free feral and domestic horses
- Mouth and head behaviours compared in ‘bitted’ and ‘bit-free’ states
• Benefits of closed-mouth breathing
- Obligate nasal breathing in the horse
- Maximising ease of airflow and respiratory gas exchange in the lungs
• Keeping a tight rein on things
- Jowl angle and obstruction of nasopharyngeal and laryngeal airflow
• “A golden bit does not make the horse any better”
- Problems and current attempted solutions, and an alternative
• Concluding comments
- Things in plain sight are sometimes invisible

Arabic Saying
He who speaks an unpalatable truth
should have one foot in the stirrup!

Hold your horses!
Chinese Terracotta Warrior Horses

Hold your horses!
Chinese Terracotta Warrior Horses
A ‘bit’ of a mouth full

Hold your horses!
Roman Riding – Hungary

Hold your horses!
Horses were domesticated – from ~ 6,000 years ago
They are large and powerful animals – deployed for many purposes
Bitted bridle use in horses’ mouths – started from ~ 2500 BC
– mainly used to control the horse
– so it could be ridden or driven safely

Hold your horses!
Horses were domesticated – from ~6,000 years ago
Today bitted bridles are still used – for control and safety
Control and safety are achieved by – by pressure applied to different
parts of the head, especially to the
– lips, interdental space, tongue,
hard palate and mandible

Hold your horses!
Horses were domesticated – from ~6,000 years ago
Today bitted bridles are still used – for control and safety
Control and safety are achieved by – by pressure applied to different
part of the head, especially to the
– lips, interdental space, tongue,
hard palate and mandible
Horse as supreme athletes – have exceptional sports versatility
For example: flat racing, steeplechase, harness racing, endurance,
cross-country, show jumping, barrel racing, roping,
polo and many other competitive events

Straight from the horse’s mouth!
Bit-induced pain (actual/threatened) – is what controls the horse
All mouth parts are richly innervated – mechanoreceptors
– thermoreceptors
– chemoreceptors
– pain receptors (nociceptors)
Sensitive mouth parts include – gums, teeth
– tongue, lips, inner cheeks
– roof of the mouth (hard palate)

Bit-induced pain (actual/threatened) – is what controls the horse
All mouth parts are richly innervated – mechanoreceptors
– thermoreceptors
– chemoreceptors
– pain receptors (nociceptors)
Sensitive mouth parts include – gums, teeth
– tongue, lips, inner cheeks
– roof of the mouth (hard palate)
Usual location of the bit – the interdental space (bars)

Skeletal evidence of marked long-term bit-induced pain
Rear: – smooth mandible from bit-free horse
Front: – after long-term bitted bridle use
– mandibular spurs and erosion;
– tooth loss and erosion
– periodontitis of empty tooth socket

Try this: – first, place a pen, bit-like, across your open mouth
– this is NOT painful even with significant pressure
– now, pull your lower lip down
– then place the pen across your gum below your teeth
– even gentle pressure applied to the pen IS PAINFUL

– this is not painful even with significant pressure
Impact of the bit: – the bit is usually located at the interdental space
– this compresses the gum of the jaw bone
– stimulates pain receptors in the gum
– strong rein tension causes MARKED PAIN

– this is not painful even with significant pressure
Impact of the bit: – the bit is usually located at the interdental space
– this compresses the gum of the jaw bone
– stimulates pain receptors in the gum
– strong rein tension causes MARKED PAIN
Pain indices: – mouth slightly or wide open; persistent jaw movements;
– teeth grinding, chewing, holding the bit between the teeth
– tongue protruding, rolling or relocated behind or above bit
– profuse salivation
– head tossing or shaking; tail swishing
– skittish body movements

Eadweard Muybridge – Animal Locomotion 1887

Race horses
Sources: YouTube videos

Hunter
Show jumper

Draught horses
Dressage
Excessive rein tension

Barrel racing

Roman Riding (Hungary)

Bit-free feral and domestic horses
Bit-free closed mouth – Feral horses
Brumby (Australia); Kaimanawa (NZ), Mustang (USA)

Bit-free closed mouth – Feral horses
Camargue (France)

Bit-free closed mouth – Domestic horses with halters

Bit-free closed mouth –
Domestic horses with bitless bridles or no bridle

Bit-induced pain-related mouth and head behaviours
Mouth slightly or widely open; persistent jaw movements;
Teeth grinding, chewing, holding the bit between the teeth
Tongue protruding, rolled or relocated behind or above bit
Profuse salivation
Head tossing or shaking; tail swishing; skittish body movements

Profuse salivation
Mouth and head behaviours when bit-free
1. Bit-induced pain-related mouth and head behaviours are absent
2. This is the case when horses are standing calmly and when exercising
3. The mouth is invariably closed when exercising at any level
4. But not when yawning, vocalising, biting, grooming, eating or drinking

Profuse salivation
Mouth and head behaviours when bit-free
1. Bit-induced pain-related mouth and head behaviours are absent
2. This is the case when horses are standing calmly and when exercising
3. The mouth is invariably closed when exercising at any level
4. But not when yawning, vocalising, biting, grooming, eating or drinking
Obvious conclusion: Bit-induced pain is eliminated.
Question: Are there additional functional benefits of the mouth-closed
(bitless) as opposed to the mouth-open (bitted) state?

Benefits of closed-mouth breathing
Upper Respiratory Tract (URT)
• The horse is an obligate nasal breather
• For fully effective respiration it MUST breathe through its nose
• At maximum, 1800-2000 L of air must flow in and out per minute

• For the best airflow the URT needs to be as ‘open’ as possible
• Even partial obstructions impede airflow and high athletic performance
• Soft palate ballooning/displacement (laryngeal and tracheal problems)

• Stabilising the soft palate against negative inspiratory pressure is important
• This requires negative pressure in the oral cavity and oropharynx
• Achieved by swallowing and then keeping the mouth closed

• Bit-induced mouth-open behaviour acts to prevent the maintenance of
negative oropharyngeal pressure and palatal stability
• This is the case both with a slightly open mouth and a wide open mouth

Keeping a tight rein on things
Jowl Angle
• The main points here are that:
- Rein tension together with actual or threatened bit-induced pain sets the
jowl angle of ridden or driven horses
- The greater the rein tension the greater the bit-induced pain
- The greater the rein tension, usually, the lower the jowl angle

Jowl Angle
• The main points here are that:
- Rein tension together with actual or threatened bit-induced pain sets the
jowl angle of ridden or driven horses
- The greater the rein tension the greater the bit-induced pain
- The greater the rein tension, usually, the lower the jowl angle
• The lower the jowl angle:
- The more nasopharyngeal airflow is obstructed
- The more exchange of respiratory gases is impeded in the lungs
- The greater is exercise intolerance at lower levels of exertion

Jowl Angle
125o
87o
75o 33o
Gallop:
low rein tension
Gallop:
moderate rein
tension
Show jumping:
strong rein tension
Dressage:
Very strong rein
tension
NPA = 100% NPA = ~90%
NPA = ~55% NPA = ~30%
LCA = 92% (-8%)
NPA = Nasopharyngeal area
LCA = Laryngeal cross-sectional area

Jowl Angle
• The ‘at rest’ jowl angle is ~90o
• The jowl angle is controlled by the rider or driver using rein tension

Jowl Angle
A. ‘Low rein tension, extended jowl angle’ (~125o):
• Straightens and widens nasopharynx
• Stretches and straightens the extrathoracic trachea making it less subject to
dynamic narrowing during inspiration
• This disproportionately decreases airflow resistance compared to that at ~90o

Jowl Angle
B. ‘Moderate rein tension, reduced jowl angle’ (~87o):
• Reduces the nasopharyngeal area by ~10%
• Disproportionately increases airflow resistance

Jowl Angle
C. ‘Strong rein tension, markedly reduced jowl angle’ (~75o):
• Markedly increases airflow resistance

Jowl Angle
C. ‘Strong rein tension, markedly reduced jowl angle’ (~75o):
• Markedly increases airflow resistance
D. ‘Very strong rein tension, severely reduced jowl angle’ (~33o)
– Rollkur position (< 33o)
• Reduces laryngeal cross-sectional area by 8%
• Very markedly increases airflow resistance

“A golden bit does not make the horse any better”
Some behaviour problems and attempted solutions
Some bit-induced pain-associated mouth and head behaviours
have been linked to poor athletic performance or control

Problem: Mouth slightly or widely open
Response: Use of tightly applied nose band
Problem: Tongue protruding, rolled or relocated behind or above bit
Response: Use of tongue ties, jointed bits, overlying flanges on the bits

Problem: Head tossing or shaking; elevated head carriage
Response: Use of martingales of different varieties
Problem: Teeth grinding, chewing, holding the bit between the teeth
Response: Variable, and usually directed at factors other than the bit

Multiple ‘solutions’ to bit-induced problems
https://www.paulickreport.com/news/thoroughbred-racing/mendelssohn-
well-behaved-while-stretching-his-legs-before-cigar-mile/

Problem: Head tossing or shaking; elevated head carriage
Response: Use of martingales of different varieties
Problem: Teeth grinding, chewing, holding the bit between the teeth
Response: Variable, and usually directed at factors other than the bit
Could the solution be as simple as ‘going bit-free’?

Multiple ‘solutions’ to bit-induced problems
In Germany racing rules apparently do not require use of a bit.
Shown here is a horse racing bit-free.
The horse’s lips are sealed, there is no drooling and the head and neck are
comfortably extended. The jockey is riding with a loose rein.
(Photo courtesy of Emma Preikschat).

Areas considered
• High performance horses as supreme athletes
- Domestication, breeding and principal outcomes
- Physiological foundations of superior athletic performance
• Key features of respiratory function
- Upper respiratory tract (URT) – general information / jowl angle / URT disorders
- Changes in blood gas levels and pH
- Lower respiratory tract (LRT) disorders – e.g. EIPH (NPPO, IAD)
• “Breathlessness” and its three types
- Key Factors
- Respiratory effort and high airflow resistance
- Air hunger and chemoreceptor-induced drive to breathe
- Simultaneous occurrence of both types
- Chest tightness and LRT inflammation (equine asthma)
• Concluding comments
- Things in plain sight are sometimes invisible

Concluding Comments:
Things in plain sight are sometimes invisible
• Having a bit or bits in the mouth is aversive:
• Most horses wearing bits show clear behavioural evidence of such aversion
• The particular behaviours indicate pain experience that is often severe

• Commonly seen when reins are used to control speed, agility and direction in
timed events, and in slow-speed events focussed on deportment, comportment
and demeanour
• Bit-free feral and other horses exhibit no such behavioural evidence

• Commonly seen when reins are used to control speed, agility and direction in
timed events, and in slow-speed events focussed on deportment, comportment
and demeanour
• Bit-free feral and other horses exhibit no such behavioural evidence
• The evidence, filmed independently, is objectively observable on YouTube
• If you doubt it, look at the evidence yourself and draw your own conclusions
• Note that supportive skeletal evidence is also available

• “Familiarity breeds invisibility”
• Dairy farmers grossly underestimate lameness in their cows until educated
• They identified only seriously lame cows: 5-10%
Whereas actually lame cow amounted to: 50-70%
• They stated that, beforehand, they thought dairy cows just “walk that way”

• “Familiarity breeds invisibility”
• Dairy farmers grossly underestimate lameness in their cows until educated
• They identified only seriously lame cows: 5-10%
Whereas actually lame cow amounted to: 50-70%
• They stated that, beforehand, they thought dairy cows just “walk that way”
• The same likely applies to unrecognised bit-associated pain-related behaviours
• From the time we first learnt to ride, they were always present
Only comparatively recently has
their significance been better understood

Concluding Comments (continued):
Inaction in the face of such invisibility is understandable
Inaction following such recognition is unacceptable
Recognition of such problems brings with it
a responsibility to act
Question:
What actions should we take?

Equine welfare during exercise: Do we have a 'bit' of a problem? #horsewelfare

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