Bit type exerts an influence on self-controlled rein tension in unridden horses

Abstract

Bit configuration and acting rein forces play a crucial role in oral health and comfort of ridden horses. Although it is a big animal welfare issue, dynamic response of horses to different bits has yet not been thoroughly investigated. This convenience sample experimental study describes a model to overcome the almost uncontrollable influence of riders on rein tension and evaluates self-controlled maximum side rein tension of ten sound horses randomly bitted with a double-jointed (DJS) and a version of a Mullen mouth snaffle-bit under unridden conditions. Horses were exercised at walk and trot on a horizontal treadmill wearing custom made force-sensing resistors (FSR) equipped to side reins. FSR were synchronized with a camera-based motion analysis system providing information on amplitudes and temporal occurrence of self-controlled maximum side rein tensile forces during different phases of separated motion cycles. The DJS exhibited larger side rein tension, indicating higher bit contact. Constant temporal occurrence of monophasic maxima at walk and biphasic maxima at trot could be observed in both bits. Within the limitations of this study, application of FSR linked to side reins in unridden horses may provide a promising tool when studying subjective response of horses to different bits.

Risk factors for bit‐related lesions in Finnish trotting horses

“…Snaffle‐bitted racehorses had more lesions than did gag‐bitted polo ponies, 2 and 11‐mm Myler‐bitted ridden horses were less stressed and expressed less head‐tossing than horses ridden with a traditional 18‐mm snaffle bit 8 . Unridden horses on a treadmill independently applied higher rein tension with a double‐jointed bit compared with an unjointed but curved mullen mouth snaffle bit 9 …”

“…8 Unridden horses on a treadmill independently applied higher rein tension with a double-jointed bit compared with an unjointed but curved mullen mouth snaffle bit. 9 Horses can be controlled without a bit during exercise, 10 but bitting is considered an obligatory safety measure in harness racing.…”

Guidelines for the Measurement of Rein Tension in Equestrian Sport

“…The two spikes within each stride are, however, often different in magnitude. A study using side reins reported a single large spike in the rein ipsilateral to the forelimb as it leaves the ground coordinated with a smaller spike in the contralateral rein [8]. The graph shown in Figure 1 has a higher spike in the rein ipsilateral to the forelimb leaving the ground and a smaller spike in the contralateral rein.…”

“…The graph shown in Figure 1 has a higher spike in the rein ipsilateral to the forelimb leaving the ground and a smaller spike in the contralateral rein. This may relate to the fact that walking horses display some lateral movement of the head between left and right forelimb stance phases [8] and that when side reins are used, there is no compensation for asynchronous changes in tension as there might be with a rider.…”

“…The body reaches its lowest point in the middle of diagonal stance, after which the head and neck continue their descent until the nuchal ligament and dorsal cervical musculature restrain the downward motion and raise the neck. Rein tension increases as the head descends relative to the base of the neck and maximal tension coincides with the lowest point of the head, which occurs during the second half of each diagonal stance phase [6,8,9] (Figure 1). Coordinated movements of the rider's shoulder and elbow joints allow the wrist to maintain a consistent position relative to the bit, changing by <15 mm during each stride [10] as the rider's hands follow the bit.…”