Is it time for chronic non-bleeding ulcers from bit use to be specifically addressed in international horse sport regulations?
Researchers raised the question in a Danish study that explored mouth-related lesions in competition horses.
“Blood coming from the horse’s mouth takes on special importance under International Equestrian Federation rules (FEI) that, in most cases, require elimination of a horse that has blood in its mouth, but with some differences between disciplines,” Mette Uldahl and her fellow researchers wrote in the journal Animals.
“Chronic non-bleeding ulcers from use of the bit are not specifically addressed in the regulations.”
However, the absence of bleeding in the horses in their study, even in those with severe lesions, implies that it may be insufficient for equestrian sport governing bodies to address only bleeding as an evaluation factor, they said
Abrasion of the skin should equally be seen as a decisive factor in an evaluation of fitness to compete, they added.
The researchers were commenting after mouth-related lesions were recorded in 342 dressage, showjumping and eventing horses and ponies presented for a mandatory pre-competition veterinary examinations before competing in the Danish National Championship in 2020.
The authors found that mouth lesions were primarily located inside the corners of the lips – the inside commissures – without associated bleeding.
If a lesion was found at the lip commissures on one side, there was an increased risk of finding a similar lesion on the other side. The anatomical location of the lesions suggested bit-related trauma, they said.
At the lip commissures, external skin-related ulcers were correlated with ulcers inside the mouth, and also with scarring/depigmentation.
Erosion or contusions at the lip commissures was associated with similar lesions on the bars, and ulcers of the mouth lining were also associated with ulcers on the bars.
Dental hooks or sharp enamel points on one side were associated with similar issues on the other side, they reported.
Dental findings were not related to mucosal ulcers or erosion/contusion at the lip commissures, but were associated with scarring and depigmentation.
Of the 342 horses, 314 (or 92%) had no ulcers inside their lip commissures. Twenty horses (6%) had an ulcer on one side, and eight horses, comprising the remaining 2%, had ulcers on both sides.
In all, 326 of the horses (95%) had ulcers on the outside of their lip commissures, while 13 (4%) had ulceration present on side, and the remaining three horses (1%) were affected on both sides.
Evidence of erosion or contusions on the inside commissures was at a similar level to ulcers in this area, but was found in only one horse on the outside of the commissures.
Thirty percent of the horses had scarring or depigmentation evident on their inside commissures, while 20% showed evidence of it on the outside commissures.
The researchers said most lesions affecting areas related to the bit are believed to be associated with pressure or repeated microtrauma from the bit.
“This study showed a significant correlation between findings of ulcers and scarring/depigmentation at the oral commissures, which serves as a clear indication that the two parameters are closely linked to each other and to the seat of the bit at the corners of the mouth.”
The findings pointed to wide variation in the natural oral pigmentation pattern in this area. “A few horses that had never worn a bit had pigmentation spots resembling those described as potentially pathological changes, which highlighted the difficulty of distinguishing whether pigment changes are related to bit use in individual horses.
“On the other hand, scarring was found to be a reliable indicator for previous problems with the use of the bit.”
Scarring and depigmentation indicate previous problems with the bit, they said, but evaluation in competition is concerned with welfare evaluation only on the day of competition.
The tendency for oral commissure lesions to be on both sides supports an external cause, and in this anatomical location the bit is likely to be the culprit, they said.
“The bilateral occurrence also suggests that, for many horse/rider combinations, problematic use of the bit is a general problem rather than being related to a left/right preference or handedness issue.”
The authors said their data did not show a link between dental findings, such as enamel overgrowths, with ulcers or erosion/contusions at any location. “For a full understanding and evaluation of the relation between lesions and dental findings, more research is needed.”
Badly fitted bits and poor riding have been blamed for ulceration, they noted. “Therefore, it is relevant to evaluate how the rider interacts with the horse through the bit, which is a reflection of the rider’s skill and training methodology.”
The trainer’s role should not be ignored, they added, noting that, among ponies, a small subset of trainers within this group trained half of all ponies with ulcers.
“However, many factors may influence the significance of the trainer’s role, for example, how long the trainer has been responsible for the pony/rider combination, whether more than one trainer is used by the rider, and the type of bit used during daily training.
“Further studies are needed to investigate the trainer’s influence on the occurrence of bit-related ulcers.”
All ulcers recorded during the study were classified as chronic, non-bleeding wounds, they said.
“It is important to understand that ulcers affecting areas related to the bit often develop over a substantial period of time as a result of direct pressure or repetitive microtraumas between the bit and the oral tissue rather than being caused by a sudden acute tearing of tissue, although this cannot be ruled out as a cause of the subsequent development of a chronic wound.”
Minor acute tears or disruptions of the bed of a chronic wound can result in the ulcer persisting over time, and ongoing irritation can cause inflammation, recognized as redness.
The authors encouraged active monitoring to reduce the occurrence of ulcers.
Greater awareness of the risk of mouth ulcers developing in horses from bit use might influence the prevalence of the problem, they said.
The study team comprised Uldahl, with the Vejle Equine Practice; Louise Bundgaard, with the University of Copenhagen; Jan Dahl, with Jan Dahl Consult, all in Denmark; and Hilary Clayton, with Sport Horse Science in Mason, Michigan.
Uldahl, M.; Bundgaard, L.; Dahl, J.; Clayton, H.M. Pre-Competition Oral Findings in Danish Sport Horses and Ponies Competing at High Level. Animals 2022, 12, 616. https://doi.org/10.3390/ani12050616