Study: Bit-Related Lesions Found in 52% of Eventing Horses

Finnish researchers found more horses with bit-related lesions than without—and most of the riders had no idea.

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Study: Bit-Related Lesions Found in 52% of Eventing Horses
Riders voluntarily presented their horses for mouth checks and were often surprised to learn they had bit-related lesions. | Photo: iStock
Bruises and open sores from bit use are common even in competition horses, although many riders are unaware they’ve occurred. In a study carried out at national and international cross-country events, researchers found more horses with bit-related lesions than horses without—and most of the riders had no idea.

“If horse handlers would monitor the bit area themselves and notice when their horse had lesions, they could  improve their horse’s comfort and welfare,” said Kati Tuomola, DVM, of the Research Centre for Animal Welfare in the University of Helsinki’s Department of Production Animal Medicine, in Finland.

“By giving them a rest from the bit to give the lesions time to heal and paying attention to how they’re handling the horse—educating themselves and watching their rein tension—they could prevent the lesions from becoming chronic and (protect) the horse from further pain.”

Two years ago, Tuomola and her team noted that 84% of trot-racing horses on Finnish tracks had bit lesions after the race. While the statistics were better—at “only” 52%—in eventing horses, as her team reports in Frontiers in Veterinary Science, there’s still a lot of progress to make, she said.

“Bit-related lesions definitely hurt; there is no doubt about that,” she said. “The amount of pain is difficult to evaluate, but the mouth is intensely innervated.”

More Than 200 Eventing Horses’ Tongues, Lips, and Bars Viewed

In her latest study, Tuomola investigated the mouths of 208 horses and ponies just after cross-country during seven national events and one international event in Finland. She and her assistant looked inside the horses’ mouths using only their gloved hands and a headlamp. They found that 109 horses—52%—had at least one fresh lesion, meaning it was new and probably just happened (but could have been developing for a while), she said. About 39% of the all the horses had bruising, and 19% had one or more open wounds. Lesions were mild in 22% of the horses, moderate in 26%, and severe in 4%. One horse had as many as five lesions in its mouth, she said.

Like in the trotter study, Tuomola found that mares were more likely to have moderate or severe lesions than geldings. “Different rein tensions might be behind this result,” she said. “Or it might be differences in how riders handle mares, how mares sense pain, levels of anxiousness or excitability, or wound healing. Whatever the cause, it’s very good to be aware of the fact that mares are at a higher risk, so we can be more mindful of that when working with them.”

Bits that were particularly thin or particularly thick were also associated with a greater risk for moderate to severe lesions. “This was a bit surprising, but in a way logical,” Tuomola said. Thick bits can push more on the mouth tissues, while smaller bits concentrate more force over a smaller surface, creating high pressure points, she explained.

Meanwhile, lesions of the bar (the bony gum area without teeth) were more common with unjointed bits, as her team also found in harness racing horses.

Interestingly, the scientists found no associations between the severity of lesions and the kind of noseband used, competition level, performance results, or the horse’s age, she said.

High Rates of Lesions, Low Rates of Awareness

The new investigation has revealed that bit-related lesions were six times greater than what scientists previously found in eventing horses in Denmark. But because the competition organizers in the Danish study did not allow the researchers to open the horses’ mouths, they could only report on the lesions they could see from the outside, that team stated.

In the Finnish study, the riders—who all voluntarily presented their horses for checks—were often surprised to learn that their horses had bit-related lesions, said Tuomola. “Almost everyone wanted me to show them the lesions; they wanted to see them for themselves,” she said. “Some of the riders were surprised, and some were sad. I think that the majority of them thought that there wouldn’t be anything there.”

The findings underline the importance of recognizing that the way we ride and the bits we use can damage horses’ mouths and cause them pain, even if it doesn’t look like it from the outside, Tuomola said.

“A few of the riders in our study might have been aware of the outer lip commissure (cracking) lesions, because that’s the one place that some riders monitor,” she said. However, riders should also learn to open their horses’ mouths, pay attention to signs of injury, and understand how their bits are affecting their horses’ oral health and welfare in general.

A Better Bit-Related Future for Horses?

Horses have certainly been dealing with bit-related pain for more than a century, said Tuomola. But ignoring the problem isn’t making it go away. “Bit-related lesions have been mentioned in newspaper texts and veterinary literature since at least around 1860-1890,” she said. “They’re definitely not new.”

Going forward, show organizers might encourage more welfare-friendly bit use by holding open-mouth checks rather than only looking outside the mouth, Tuomola suggested.

“It would be best if there were no lesions at all,” she said. “However, it would be a good idea to monitor the bit area at least from a few randomly drawn horses in competitions, because lesions usually don’t bleed outside the mouth. That way, they could at least prevent the horses with severe lesions from competing. This would show that mouth lesions are taken seriously in the horse industry.”


Written by:

Passionate about horses and science from the time she was riding her first Shetland Pony in Texas, Christa Lesté-Lasserre writes about scientific research that contributes to a better understanding of all equids. After undergrad studies in science, journalism, and literature, she received a master’s degree in creative writing. Now based in France, she aims to present the most fascinating aspect of equine science: the story it creates. Follow Lesté-Lasserre on Twitter @christalestelas.

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