Bit-induced pain: a cause of fear, flight, fight und facial neuralgia in the horse

Abstract

An ethological survey was based on 605 written reports from horsemen who had switched from a bitted bridle to a new bitless bridle. The comparison of equine behaviour was between an invasive and painful method of control (a bitted bridle) and a non-invasive and painless method (a bitless bridle). The unprecedented opportunity to switch a horse, overnight, from painful to painless control revealed many new and serious manifestations of the syndrome 'aversion to the bit.' The survey demonstrated that the bit method of control caused 58 adverse behavioral effects. All 58 effects could be classified under four major effects; to instill fear, to trigger flight, to make the horse fight back, and to cause facial neuralgia (the headshaking syndrome). These effects could all, in turn, be categorized as responses to oral pain. The sensory pathway for registering pain caused by the bit is the trigeminal nerve but the motor pathways involved many systems, with the nervous, respiratory and musculoskeletal systems predominating. The behavioral responses interfered, in particular, with attitude to exercise, breathing and locomotion. A survey of 65 horse skulls revealed painful, bit-induced exostoses on the mandibular diastema in 49 (75%). It was concluded that a bit is harmful to the health and safety of horse and rider, and an impediment to performance.