Acute mouth lesions seen in more that half of Eventing horses after cross-country – study

Bit-related lesions inside the mouth in the area where the upper and lower lips join. Images: Tuomola et al.

Welfare checks for bit-related mouth injuries in Eventing horses have been proposed by researchers after half the animals checked in a study after the cross-country phase were found to have acute oral lesions.

The study team in Finland also found that horses wearing thin or thick bits increased the risk of moderate or severe oral lesions.

The risk was also higher for warmbloods and coldbloods compared with ponies; and mares were at higher risk of more serious lesions than geldings.

University of Helsinki researcher Kati Tuomola and her colleagues, writing in the journal Frontiers in Veterinary Science, also reported that horses wearing unjointed bits were at higher risk of getting bar lesions than those wearing jointed bits.

If the size of the horse’s oral cavity is not known, it is advisable to choose a middle-sized jointed bit, they said, and attention should be paid to the pool of horses identified as being at greater risk of mouth injuries.

“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 since oral lesions in the bit area were common after a competition, even though no external bleeding was observed,” they said.

“In riding horses, bit-related lesions can be monitored in a competition environment with systematic oral examination by using a headlamp, unlatching nosebands and possible curb chain, and lifting the bit while examining the bars of the mandible.”

Typical bar-related lesions seen in the study. Images: Tuomola et al.

For their study, the researchers investigated the mouths of 208 Eventing horses after the cross-country phase, focusing on the area affected by the bit.

The horses, comprising 127 warmbloods, 52 coldbloods, and 29 ponies, were competing in eight events at three locations in western Finland during the summers of 2018 and 2019.

The authors noted that, under Finnish riding competition rules, horses must be bridled in the competition venue for safety reasons, so most were examined with their bridle on.

Acute lesions were observed in 52% of the animals (109 of the 208 horses).

The lesion status was graded in each horse. No acute lesions were seen in 48% (99/208) of the animals. They were assessed as mild for 22% (45/208) of the horses, and moderate for 26% (55/208) of the animals. The lesions were considered severe in 9 horses, representing 4% of the horses in the study.

Bit-related lesions outer lip commissures (where the lips join). Images: Tuomola et al.

They were most common in the inner area where the upper and lower lips join, with lesions seen here in 39% (81/208) of the horses.

Tuomola and her fellow researchers reported that bar lesions were more common in horses with unjointed bits (40%, 8 out of 20 horses) than with basic double-jointed (10%, 5/52), formed double-jointed (8%, 6/78) or single-jointed bits (5%, 2/40).

Discussing their findings, the authors noted that, even though a high occurrence of oral lesions was found in the Eventing horses, it was lower than in trotters in Finland (84%) and Sweden (88%).

Bruises were more common than wounds, they noted.

Turning to the higher lesion risks associated with thin and thick bits, the study team said several mechanisms could explain this.

Various degrees of pigment loss on outer lip commissures Images: Tuomola et al.

Thin bits, they said, may cause increased pressure on a relatively small area. In the case of thick bits, in some cases they may be too thick to fit the individual. “It has been suggested that thick bits may cause more discomfort in horses with small oral cavities,” they noted.

“Most event horses in our present study competed nationally at a low difficulty level (60–80cm). Oral lesions were unconnected to competition level, in contrast to a Danish study where the number of commissure lesions increased with competition level.

“Good performance is still often held as an indicator of good welfare. Evidence of association between lesion status and competition placement was not found in the present study and a previous study also showed no association with race performance.

“Therefore, well-performing horses are not necessarily free from welfare concerns.”

The study concluded that thin and thick bits should be considered risk factors for mouth lesions, with mares also at heightened risk.

“In addition, in this sample ponies had a 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.”

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.

Tuomola K, Mäki-Kihniä N, Valros A, Mykkänen A and Kujala-Wirth M (2021) Bit-Related Lesions in Event Horses After a Cross-Country Test. Front. Vet. Sci. 8:651160. doi: 10.3389/fvets.2021.651160

The study, published under a Creative Commons License, can be read here.

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