A Photographic Methodology for Analyzing Bit Position Under Rein Tension

Abstract

Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractBits are a common and invasive piece of equipment used in equestrian sports. A bit should be carefully chosen to suit the individual horse according to the pressure points it is willing to accept. Bit pressure is poorly understood due to a lack of accessible research instruments. The objective of this study was to describe a method to estimate pressure points from the bit on the tongue without the need for radiographs. The method employs photographic images of horses under static rein tension. Using design features on the bit, the angle at which these features press into the tongue were calculated. Ten riding school horses wearing a snaffle bridle without a noseband, were used to measure the degree to which a bit rotates under 2 kg of static rein tension for a: Turtle Top snaffle bit, French Link snaffle bit, HS single-jointed snaffle bit and ported Weymouth bit. Six dressage and eventing horses were used to measure the effect of rein tension, in 0.5 kg increments, on the degree of rotation of the bit. The bit rotated, but not significantly (P > 0.008), over the rein tensions used (up to 2kg). The reliability of the proposed method was confirmed by comparing anatomical reference lines in photographs with those in radiographs. The findings provide a reliable estimate to determine pressure points from a bit on the tongue, under rein tension without the need for invasive techniques and in the absence of technologically adequate equipment.

Mouth Pain in Horses: Physiological Foundations, Behavioural Indices, Welfare Implications, and a Suggested Solution

“…Bridles are usually adjusted so that the bit is in contact with a largely tooth-free segment of the gums on each side of the mandible, i.e., behind the incisors and in front of the premolars in the so-called "interdental space" [7,[104][105][106]. The gums are modified periosteum, i.e., the membrane that surrounds bone, and are richly supplied with nociceptors [99,107].…”

“…It is beyond the scope of this review to consider the impact of bit design on these phenomena. Suffice it to say here that oral contact sites and thus the location and severity of lesions appear to depend on particular design features of different bits and how the bits are used [104,106,120,124,125,129,130,133]. However, with some exceptions (e.g., [106,133]), many investigations are handicapped by having to rely on horses that have been made available by owners who supply them wearing their own tack when participating in various independently scheduled equestrian activities, so that rigorous comparisons of the specific impacts of different bit types can be difficult.…”

Oral Dimensions Related to Bit Size in Adult Horses and Ponies

“…The bit causes pressure on the sensitive structures of the horse mouth: on the lip commissures, buccal mucosa, tongue and the bars of the lower jaw ( 5 – 7 ), and depending on the bit type can also cause pressure to the hard palate and the base of the second premolars ( 5 , 8 , 9 ). Pressure (p) caused by the bit, p = Force (F)/Area (A), is related to the weight of the bit mouthpiece, cheekpiece tension, rein tension applied via reins, and to the contact area of the bit with the oral structures ( 3 , 10 ). The noseband or other accessory equipment may affect rein tension, and thus the bit pressure ( 11 ).…”

“…The incisors and second premolar teeth together with the lip commissures limit the location of the bit in the rostro-caudal direction ( 20 ). The bit is mobile inside the mouth ( 5 , 10 ). Within the anatomical limitations, a horse can move the bit with its tongue and lips, and the rider or driver can move it by exerting rein tension, thus affecting the bit-tongue angle ( 10 ) and bit pressure distribution inside the mouth ( 5 – 7 , 9 , 20 ).…”

“…Previous studies related to bit and bridle fit have focused on bit position and action in the mouth ( 4 – 7 , 9 , 10 , 22 ) and have described oral trauma caused by the bit ( 13 – 17 ). However, one study with 72 cavader horse heads reported considerable variation in oral dimensions between horses with respect to position and size of a snaffle bit ( 20 ).…”