Bit-related lesions research page 

Research findings and media in english

Main research findings 2017-2022

  1. Bit-related lesions (bruises and wounds) were common after a race or competition despite only six trotters out of 261 showed external mouth bleeding.
  2. Trotters had more lesions and lesions of greater severity than event horses. Bruises and wounds were find in 84% of the trotters and 52% of the event horses after a competition. Of the trotters 20% and event horses 4% had severe wounds in the bit area. 
  3. Of the trotters 10% had blood on the bit or inside the mouth. Only one event horse of 208 examined had blood inside the mouth. 
  4. The most common lesion locations were: inner lip commissure, bars of the mandible, buccal area near 106 and 206 teeth, outer lip commissure.
  5. Oral examination and the lesion scoring system for bit-related lesions were suitable for field conditions.
  6. Video recordings from lesions were more suitable than photographs for documenting oral lesions.
  7. Crescendo bit, unjointed mullen mouth regulator bit, and straight plastic bit (model Happy Mouth) and female sex (mare) were recognized as risk factors for moderate or severe oral lesions in trotters.
  8. In event horses, thin or thick bits, mare sex, and breed other than pony were risk factors.
  9. Horses wearing unjointed bits were at higher risk of sustaining bar lesions than horses wearing jointed bits.
  10. Results may at least partly reflect driveability or rideability issues, and thus, rein tension differences because drivers or riders may change to distinctive bit designs if they have difficulty eliciting an appropriate response with rein cues.
  11. Results encourage adopting bit area monitoring as a new routine by horse handlers and as a welfare measure by competition organizers in order to minimize pain and negative experiences by early diagnosis and treatment of mouth lesions. (For example 5% of the competition horses examined after a competition).
  12. The pilot questionnaire study on "Horse industry stakeholders' attitudes towards bit-related lesions in harness racing horses" indicated differences in attitudes towards bit-related lesions between stakeholder groups but also within a group. This might reflect differences in conflicts of interests, moral values, empathy, or over-exposure to oral lesions. Not removing horses with severe oral lesions from the race may compromise horse welfare and undermine trust in the surveillance system.

Critical points for performing reliable bit area examination

Bit-related lesions (wounds and bruises) are inside the mouth and (1) don't usually bleed outside. Therefore lesions can only be found by adequate oral examination. It is important to perform the examination (2) with the headlamp and to carefully examine the (3) contralateral  (opposite side) inner lip commissures by holding the tongue, bars, outer lip commissures, and rostral buccal area. (4) Removal of all head equipment before the examination in trotters is critical. (5) In riding horses the examination is preferable done without bit and bridle, however it is possible to perform examination reliably by opening the noseband and curb chain and lifting the bit. (6) Careful palpation and visual assessment of the bars and the area in front of the lower cheek teeth is necessary since some of the bar lesions are hidden behind swollen mucosal folds and thick mucus. In some cases, bar lesions may become visible only after the (7) mucosal fold is pulled rostrally with the finger. 

Bit-related lesions and risk factors in competing trotters and event horses - thesis

Peer-reviewed publications

  1. Tuomola, K., Mäki-Kihniä, N., Kujala-Wirth, M., Mykkänen, A., and Valros, A. (2019) Oral Lesions in the Bit Area in Finnish Trotters After a Race: Lesion Evaluation, Scoring and Occurrence. Front. Vet. Sci. 6:206. doi: 10.3389/fvets.2019.00206.
  2. Tuomola, K., Mäki-Kihniä, N., Valros, A., Mykkänen, A., and Kujala-Wirth, M. (2021) Risk factors for bit-related lesions in Finnish trotting horses. Equine Vet J. 53: 1132- 1140. doi: 10.1111/evj.13401.
  3. Tuomola, K., Mäki-Kihniä, N., Valros, A., Mykkänen, A., and Kujala-Wirth, M. (2021) Bit-related lesions in event horses after a cross-country test Front. Vet. Sci. 8:651160. doi: 10.3389/fvets.2021.651160.

Mouth examination video 2017  (4 min)

Research in Media

EVJ Infographics 2021

ISES congress Poster, Hartpury UK 2022

Research funding - grants

  • Trotting and Breeding Agency
  • Finnish Foundation of Veterinary Research
  • Finnish Veterinary Foundation (Mercedes Zachariassen Foundation)
  • Finnish Cultural Foundation (Pirkanmaa regional fund)
  • Orion Research Foundation,
  • Juliana von Wendt Foundation
  • Heli Castrén grant (SEY Animal Welfare Finland)
  • Erkki Rajakoski Foundation
  • Doctoral School in Health Sciences, University of Helsinki


8/12/2021 Finnish Veterinary Assocation - Animal Welfare Award

8/12/2021 Poster award 2nd place. 

In swedish - på svenska