Vibrissae of the horse, a pilot study on how to assess the effect of manipulation.
Bergen, A.P.I. van
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Abstract Introduction: The horse' s vibrissae are often trimmed for cosmetic purposes in the Netherlands. The function of vibrissae has been studied in certain rodents and sea mammals, but not in horses. To assess the effect of trimming vibrissae on the welfare of horses, the vibrissae' s function in the horse must first be studied. However, no standardized test is available. The primary aim of this pilot study was to find parameters that could both measure the function of the horse' s vibrissae as well as the effects of trimming them. The secondary aim was to create a standardized test, which would allow their function to become apparent. To this end, two tests were performed. Test 1: Materials and method: Five stimuli were applied to the vibrissae of 14 horses: heat, cold, electricity, damage and traction. All stimuli and their control (i.e. ' sham' ) stimuli were applied for 5 seconds each, in a randomized order. Behavior and heart rate were analyzed. Results: No significant heart rate results were seen. Results on behavior are not yet available. Conclusion: These results could indicate that horses do not sense the applied stimuli with their vibrissae. However, heart rate might not be the right outcome measure. Test 2: Materials and method: Multiple devices were designed and evaluated for usability. The best device was a design that was adjustable to the circumference of the horse' s muzzle plus 1 cm. Horses were randomly divided into three groups. Group 0: vibrissae trimmed to 0 cm (N=16), group 1: vibrissae trimmed to 1 cm (N=13), group 2: vibrissae kept at natural length (N=14). All horses were asked to move their nose through the device. Behavior, nose-bumps, heart rate, heart rate variability and latency time were investigated. Results: Results on behavior and latency time are not yet available. Available data showed a large within group variation. There was no significant difference between the means of the three groups. Conclusion: Due to a small power of our test, no conclusions can be drawn from these results regarding the effect of trimming vibrissae on the used parameters. Analyzed parameters do not appear to be useful outcome measures. Because not all results are available yet, the usability of the designed device is still under debate.