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Home / Equine Research Bank / Equine Vet J / A bitless bridle does not limit or prevent dynamic laryngeal...
Equine veterinary journal2020; 53(1); 44-50; doi: 10.1111/evj.13287

A bitless bridle does not limit or prevent dynamic laryngeal collapse.

Abstract: Bits have often been incriminated as a cause of upper respiratory tract obstruction in horses; however, no scientific studies are available to confirm or refute these allegations. Clinical signs of dynamic laryngeal collapse associated with poll flexion (DLC) are induced when susceptible horses are ridden or driven into the bit. Objective: To determine whether use of Dr Cook's™ Bitless Bridle, instead of a conventional snaffle bit bridle, would reduce the severity of DLC in affected horses measured objectively using inspiratory tracheal pressures. Methods: Intervention study using each horse as its own control in a block randomised order. Methods: Nine Norwegian Swedish Coldblooded trotters previously diagnosed with DLC were exercised on two consecutive days using a standardised high-speed treadmill protocol with either a conventional bridle with a snaffle bit, or Dr Cook's™ Bitless Bridle. Head and neck position, rein tension, inspiratory tracheal pressure measurements, and laryngeal videoendoscopy recordings were obtained. A heart rate greater than 200 bpm, and similar degrees of poll flexion/head height, had to be achieved in both bridles for the individual horse's data to be included for comparison. Results: Seven horses' data met the inclusion criteria. The change in mean inspiratory tracheal pressure between free and flexion phases in the bitless bridle (-15.2 ± 12.3 cmH2 O) was significantly greater (P < .001) than in the snaffle bit bridle (-9.8 ± 7.9 cmH2 O). Mean inspiratory pressure during the free phase was significantly (P < .001) more negative with the snaffle bit bridle (-32.3 ± 6.3 cmH2 O), vs the bitless bridle (-28.5 ± 6.9 cmH2 O). Mean pressures in flexion phase, snaffle bridle (-42.1 ± 10.8 cmH2 O), vs bitless bridle (-43.7 ± 15.6 cmH2 O) where not significantly different between bridles (P = .2). Conclusions: Small sample size due to difficulty recruiting suitable clinical cases. Conclusions: This study could not provide any clear evidence that the effect of a snaffle bit in a horse's mouth influences the development or severity of DLC. Instead, head and neck angles induced by rein tension seem to be the key event in provoking DLC in susceptible horses.
© 2020 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2020-06-17 PubMed ID: 32449540DOI: 10.1111/evj.13287Google Scholar: Lookup
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Summary

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The research investigates whether Dr. Cook’s Bitless Bridle, compared to a conventional snaffle bit bridle, would decrease the severity of dynamic laryngeal collapse in horses. The study found no clear evidence that the use of a snaffle bit influences the development or severity of this condition, suggesting that the angle of the horse’s head and neck induced by rein tension may play a more significant role.

Objective and Methods

  • The main goal of this study was to determine if using Dr. Cook’s Bitless Bridle could reduce the severity of dynamic laryngeal collapse (DLC) in horses. The hypothesis was based on the common speculation that bits could cause upper respiratory tract obstruction in horses.
  • The researchers used an intervention study design where every horse served as its own control. Nine horses from Norwegian Swedish Coldblooded trotters, all previously diagnosed with DLC, were exercised on two consecutive days. In each session, they used either a conventional bridle with a snaffle bit, or Dr Cook’s Bitless Bridle.
  • To ensure accuracy and consistency in monitoring, the researchers ensured that every horse had to achieve a heart rate greater than 200 bpm and similar degrees of poll flexion/head height in both bridles for their data to be included in the comparison.
  • The researchers measured head and neck position, rein tension, inspiratory tracheal pressure, and recorded a laryngeal videoendoscopy. These measurements helped them objectively evaluate the severity of DLC in the horses.

Results

  • The criteria for inclusion was met by seven horses’ data. The researchers noted a greater change in mean inspiratory tracheal pressure in the bitless bridle than in the snaffle bit bridle when comparing their free and flexion phases. Furthermore, mean inspiratory pressure during the free phase was more negative with the snaffle bit bridle. However, they found no significant differences between the two bridles during the flexion phase.
  • Despite the greater difference in inspiratory pressure change with the bitless bridle, the study could not provide clear evidence that a snaffle bit in a horse’s mouth influences the development or severity of DLC.

Conclusions

  • Due to the difficulty of recruiting suitable clinical cases, the study had a small sample size, which might limit the strength of its conclusions.
  • The results suggested that head and neck angles induced by rein tension seem to be the key factor in provoking DLC in susceptible horses rather than the use of a snaffle bit. This emphasis on angulation and tension could contribute to new training methods and potential ways to manage or reduce the severity of DLC in horses.

Cite This Article

APA
Fretheim-Kelly Z, Fjordbakk CT, Fintl C, Krontveit R, Strand E. (2020). A bitless bridle does not limit or prevent dynamic laryngeal collapse. Equine Vet J, 53(1), 44-50. https://doi.org/10.1111/evj.13287

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 53
Issue: 1
Pages: 44-50

Researcher Affiliations

Fretheim-Kelly, Zoe
  • Faculty of Veterinary Medicine, Companion Animal Clinical Sciences, Norwegian University of Life Sciences, Oslo, Norway.
  • Haukeland University Hospital, Bergen, Norway.
Fjordbakk, Cathrine T
  • Faculty of Veterinary Medicine, Companion Animal Clinical Sciences, Norwegian University of Life Sciences, Oslo, Norway.
Fintl, Constanze
  • Faculty of Veterinary Medicine, Companion Animal Clinical Sciences, Norwegian University of Life Sciences, Oslo, Norway.
Krontveit, Randi
  • Norwegian Medicines Agency, Oslo, Norway.
Strand, Eric
  • Faculty of Veterinary Medicine, Companion Animal Clinical Sciences, Norwegian University of Life Sciences, Oslo, Norway.

MeSH Terms

  • Airway Obstruction / veterinary
  • Animals
  • Horse Diseases / prevention & control
  • Horses
  • Larynx
  • Norway
  • Sweden

Grant Funding

  • Faculty of Veterinary Science, Norwegian University of Life Sciences

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