The effect of double bridles and jaw-clamping crank nosebands on temperature of eyes and facial skin of horses
Publication Type: |
Journal Article |
Year of Publication: |
2012 |
Authors: |
Paul McGreevy, Amanda Warren-Smith, Yann Guisard |
Publication/Journal: |
Journal of Veterinary Behavior: Clinical Applications and Research |
Keywords: |
bridle, equitation science, horse welfare, jaw clamping, nosebands, vascular perfusion |
ISBN: |
1558-7878 |
Abstract:
Any apparatus that restricts a horse’s movement can compromise welfare. Eye temperature as measured remotely using infrared thermography is emerging as a correlate of salivary cortisol concentrations in horses. This article explores the effect on the temperature of the eyes and facial skin of horses wearing devices that restrict jaw movements. In certain equestrian disciplines, unacceptable equine oral activity, such as gaping of the mouth, is penalized because it reflects poor training and lack of compliance. This explains the wide range of nosebands and flash straps designed to prevent the mouth opening. Some of these nosebands are banned from higher-level dressage competitions in which double bridles are mandatory, possibly because they are regarded as restrictive. Nevertheless, the current international rules overlook the possibility that noseband can appear innocuous even though some designs, such as the so-called crank noseband, can be ratcheted shut to clamp the jaws together. Some equestrian manuals and competition rule books propose that “two-fingers” be used as a spacer to guard against overtightening of nosebands but fail to specify where this gauge should be applied. The vagueness of this directive prompted us to undertake a small random survey of the finger dimensions of adult men (n = 10) and women (n = 10). There were significant sex differences in the measurements of fingers of adults (P < 0.001), thus illustrating that the “two-finger rule” is not a reliable guide for standardized noseband fastening. Infrared thermography was used to measure the temperature of facial skin and eyes of adult horses (n = 5) wearing a double bridle with and without a cavesson noseband. A taper gauge was developed based on the mean circumference of adult index and middle fingers (9.89 ± 0.21 cm), and this was used as a spacer at the nasal planum or beside the mandible when tightening the noseband. The nosebands were fastened significantly tighter when the taper gauge was used beside the mandible than at the nasal planum (P = 0.02). Wearing double bridles and nosebands that had been tightened with and without the taper gauge caused an increase in eye temperature compared with baseline values (P = 0.012), and the tighter the noseband was fastened, the cooler the facial skin of the horse (and, presumably, the greater the impairment of vascular perfusion) when compared with baseline values (P = 0.016). This study suggests that horses wearing double bridles and tight nosebands undergo a physiological stress response and may have compromised vascular perfusion. Consequently, on welfare grounds, the use of nosebands that cause any constriction of jaw movement should be reviewed as soon as possible.