Bit-Related Lesions in Event Horses After a Cross-Country Test

Abstract

Bit-related oral lesions are common and may impair horse welfare. The aim of this study was to investigate the prevalence of oral lesions and their risk factors in a sample of Finnish event horses. The rostral part of the oral cavity (the bit area) of 208 event horses (127 warmbloods, 52 coldbloods, and 29 ponies) was examined in a voluntary inspection after the last competition phase, i.e., the cross-country test. Acute lesions were observed in 52% (109/208) of the horses. The lesion status was graded as no acute lesions for 48% (99/208), mild for 22% (45/208), moderate for 26% (55/208) and severe for 4% (9/208) of the horses. The inner lip commissure was the most common lesion location observed in 39% (81/208) of the horses. A multivariable logistic regression model with data of 174 horses was applied to risk factor analysis. Horses wearing thin (10–13 mm) (OR 3.5, CI 1.4–8.7) or thick (18–22 mm) (OR 3.4, CI 1.4–8.0) bits had a higher risk of moderate/severe lesion status than horses wearing middle-sized (14–17 mm) bits (P = 0.003). Breed was associated with moderate/severe lesion status (P = 0.02). The risk was higher for warmbloods (reference group) and coldbloods (OR 2.0, CI 0.88–4.7) compared with ponies (OR 0.2, CI 0.04–0.87). Mares were at higher risk of moderate/severe lesion status (OR 2.2, CI 1.1–4.5) than geldings (reference group) (P = 0.03). Bar lesions were more common in horses with unjointed bits (40%, 8/20) than with basic double-jointed (10%, 5/52), formed double-jointed (8%, 6/78) or single-jointed bits (5%, 2/40) (Fisher's exact test, P = 0.002). The results of this study suggest that thin and thick bits and mare sex should be considered risk factors for mouth lesions. In addition, in this sample ponies had smaller risk for lesions than other horse breeds. We encourage adopting bit area monitoring as a new routine by horse handlers and as a welfare measure by competition organizers for randomly drawn horses.

Assessment of Skin and Mucosa at the Equine Oral Commissures to Assess Pathology from Bit Wear: The Oral Commissure Assessment Protocol (OCA) for Analysis and Categorisation of Oral Commissures

“…Potentially pathological pigment changes were correlated to the horse’s level of training, with more findings in highly trained horses. This finding is consistent with other studies showing a higher frequency of lesions at the oral commissures in horses performing at higher levels [ 5 , 6 , 8 ]. Horses that had never been bitted showed a lower frequency of these changes.…”

“…The frequency of ulcers was also low in our study with one occurrence in a horse at a high training level, four at low/intermediate training level, and none in the group of untrained horses that had not been bitted. From other studies, we have evidence of ulcers occurring primarily in horses competing at a high level in dressage [ 6 ], eventing [ 5 ], Icelandic competitions [ 7 ], trotting races [ 4 ], galloping races [ 2 ] and polo [ 2 ]. A low frequency of findings can be expected in a mixed population of horses primarily being trained at low to intermediate levels as in this study.…”

“…The most frequently reported type of pathological lesion associated with bit use is oral ulceration [ 2 , 3 , 4 , 5 , 6 ]. Ulcers were also reported in horses that had not been bitted or ridden for 11 months, but these were smaller and less numerous than in ridden horses [ 3 ].…”

“…In that study, horses competing at higher levels showed lesions more frequently but there was no association between the use of a bit or type of bit [ 6 ]. In event horses, evaluated after completion of the cross-country phase, 52% had acute oral injuries, and 39% of the lesions were located on the inner aspect of the oral commissures [ 5 ]. Horses wearing bits with a thick (>17 mm) or thin (<14 mm) mouthpiece diameter were at greater risk of severe lesions in that study.…”

Oral Dimensions Related to Bit Size in Adult Horses and Ponies

“…A bit that does not fit can potentially cause too much pressure, pinching or rubbing of oral tissues ( 12 ) or restrict tongue movement ( 7 ). An ill-fitting or inexpertly used bit can cause oral trauma ( 13 – 17 ) and thus discomfort or pain for the horse ( 3 , 18 ). Oral discomfort can lead to undesirable behavior such as avoiding the bit pressure by opening the mouth and protruding the tongue, or resisting bit pressure by grasping the bit between the teeth ( 1 , 4 , 7 ).…”