During difficult veterinary procedures, like scoping and other invasive treatments, it is often necessary to physically restrain the horse for its own and the vet staff’s safety. But, do lip and ear twitches actually sedate the horse or do they restrain through pain? And does their use carry any negative consequences? In a recent study, Benjamin Flaköll and his team of researchers set themselves the task to find out by examining 12 geldings that hadn’t experienced twitching previously, and after examining the data, they warn that ear twitching should be actively discouraged.
The study titled: Twitching in veterinary procedures: How does this technique subdue horses? by Benjamin Flakoll, Ahmed Ali and Carl Saab was presented at the 2016 Equitation Science Conference in Saumur, France and was published last October in the Journal of Veterinary Behaviour.
In regards to the stress related measures, HR, HRV and SC, they found that, in the ear twitch group, they increased significantly for the duration of the procedure, indicating a stress response and suggesting that the ear twitch immobilises the horse causing it to 'freeze' through fear and pain (although the researchers also acknowledge there is no direct way to ascertain and measure pain in horses).
In the lip twitch group, HR and HRV significantly decreased during the first five minutes, indicating a lower stress level during the initial phase of twitching, and supporting the notion of an analgesic effect but, importantly, they increased after five minutes to the same level as the ear twitch. This supports anecdotal reports that the twitch must only be used for short periods and procedures of short duration.
Based on the results, the researchers conclude that the lip twitch and ear twitch clearly affect horses in very different ways.
Initially, the lip twitch increases parasympathetic nervous system activity (showed by a decrease in HR and HRV) and reduced stress levels, plus it has no effect on a horse’s behaviour short or long-term. This suggests that it does subdue through a temporary calming, probably analgesic effect. However, after the first 5 minutes of application, the lip twitch appears to significantly raise the sympathetic tone (indicating a stressful response), which raises questions about its suitability for periods longer than just a few minutes.
The ear twitch, on the other hand, significantly raises sympathetic nervous system activity and stress levels and makes horses harder to handle both directly after application of the twitch and over time. These results strongly suggest that the ear twitch restrains horses through a stressful and aversive mechanism, probably fear and/or pain.
Because of these stark differences, the researchers warn that the only twitch that should be used when attempting to humanely subdue a horse is the lip twitch, and use of the ear twitch should be actively discouraged among veterinarians and others involved in equine management.
Nevertheless, if it is necessary to subdue horses for more than a few minutes, veterinarians should not use the lip twitch but should consider anaesthetizing the animal.
The abstract of the study titled: Twitching in veterinary procedures: How does this technique subdue horses? by Benjamin Flakoll, Ahmed Ali and Carl Saab is published in the Journal of Veterinary Behaviour and is available here
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