Certain bit styles linked to more mouth injuries in trotters

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The six most common bits used on trotters in the study. Image: https://doi.org/10.1111/evj.13401

Certain bits were linked to a higher risk of moderate or severe mouth lesions in a study of trotting horses in Finland.

Kati Tuomola and her fellow researchers, writing in the Equine Veterinary Journal, noted that bit‐related lesions are common in competition horses, but little evidence exists concerning potential risk factors linked to their development.

In Nordic countries, an 84% to 88% occurrence of oral lesions in the bit area after racing has been reported. However, few studies have described bit types as a risk factor.

Researchers in the University of Helsinki study set out to explore potential risk factors for oral lesions in Finnish trotters.

In particular, they wanted to investigate whether mouth lesions in a mixed population of Finnish trotting horses were associated with certain bits, trotting equipment or race performance.

A total of 261 horses were evaluated — all privately owned trotters participating in 10 separate harness racing events on four racetracks in western Finland.

The mouths of 261 horses (151 Standardbreds, 78 Finnhorses and 32 ponies) were examined after each harness race for any evidence of lesions. Information on bit type, equipment and race performance was also collected.

The horses were trained by 171 individual trainers and driven by 120 individual drivers.

The researchers found that there was a higher risk of moderate or severe oral lesion status associated with horses wearing a crescendo bit, a mullen mouth regulator bit, or a straight plastic bit, compared with horses wearing a snaffle trotting bit.

The snaffle trotting bit was the most common bit among all the breeds, worn by 98 horses. Exactly half of them — 49 — were found to have moderate or severe oral lesions after racing.

Thirty-eight horses wore a crescendo bit, with 30 (79%) showing moderate or severe oral lesions.

A mullen mouth regulator bit was worn by 25 of the horses, with 23 of them (92%) showing moderate or severe lesions.

A straight plastic bit was worn by 14 horses, all of whom showed lesions assessed as moderate or severe.

Bit thickness was not associated with lesion status.

Mares had a higher risk for moderate or severe lesions than did geldings, with stallions recording a similar prevalence to geldings.

Bar lesions were seen in 67 horses. These were more common in horses wearing unjointed bits than in horses wearing jointed bits.

Lesions in the buccal area and the inner lip commissures were not associated with bit type, the study team reported.

The snaffle trotting bit was the most common bit among all the breeds, worn by 98 horses. Half of them - 49 - were found to have moderate or severe oral lesions after racing.
The snaffle trotting bit was the most common bit among all the breeds, worn by 98 horses. Half of them – 49 – were found to have moderate or severe oral lesions after racing. Image by Scottslm

Using a tongue‐tie or an overcheck, galloping during the race, a finish in the top three, or money earned in the race was also not associated with lesion risk.

The authors noted that while trends were observed with certain bit styles, lesions were observed regardless of bit type.

“Good performance does not guarantee good welfare, even though that still is a common belief,” the study team said in discussing their findings.

Horses with moderate or severe mouth lesions were placed in the top three or earned money in the race similarly to horses with mild or no lesions.

Lesions, although potentially painful, do not necessarily manifest in poor performance, they said.

“Currently, it is not fully understood how negative experiences from lesions are linked to the horse’s behaviour later on during their competition career, nor is the safety risk for humans fully appreciated.

“However, learning and mood are affected by all experiences, and pain or discomfort can elicit a fear reaction, acute stress response and, later, anticipatory stress in the competition environment.”

“‘Flightiness’ is a trait that some might consider advantageous to a racehorse to a certain degree, but it can constitute risk for accidents.”

The researchers said further studies on rein tension, the interaction between bit type and rein tension, and prevention of mouth lesions in trotters are warranted.

The study team comprised Tuomola, Anna Valros, Anna Mykkänen and Minna Kujala‐Wirth, all with the University of Helsinki; and Nina Mäki‐Kihniä, an independent researcher in Pori, Finland.

» Related article: Bit injuries prevalent among Finnish trotters, study finds

Risk factors for bit‐related lesions in Finnish trotting horses
Kati Tuomola, Nina Mäki‐Kihniä, Anna Valros, Anna Mykkänen and Minna Kujala‐Wirth
Equine Veterinary Journal, December 17, 2020 https://doi.org/10.1111/evj.13401

The study, published under a Creative Commons License, http://creativecommons.org/licenses/by/4.0/ can be read here.

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