Such bone remodeling is not evidence of cause-and-effect but suggests horses might be damaging their own skulls “in a bid to seek comfort” under tightened tack, said Paul McGreevy, BVSc, PhD, MRCVS, MACVS (Animal Welfare), professor of animal behavior and animal welfare science at the University of Sydney, in Australia.
“If bit pressure prompts a horse to open his mouth in search of relief from the pressure but is denied comfort because of a restrictive noseband, he may not simply give up but may just keep working against the stricture of the noseband” said McGreevy, who received a 2020 Global Animal Welfare Award from the World Veterinary Association on Nov. 2. “My fear is that these lesions may be evidence of animals in training, competition, or work who are essentially mutilating themselves.”
McGreevy and his fellow researchers, including Lucia Pérez-Manrique, DVM, of the National Autonomous University of Mexico in Mexico City, examined the heads of nearly 150 Warmblood riding horses. As part of the Equine High-Performance Centre (CEAR) of the country’s military cavalry, the horses perform in dressage, show jumping, eventing, and military processions. The veterinary scientists visually inspected and palpated (felt) the horses’ faces and then conducted radiographic imaging of the skulls to check for abnormalities in the nasal and jawbones.
As confirmed by two specialist veterinary radiologists who examined the horses’ radiographs independently, the team found that 37% of the horses had at least one lesion on the nasal bone, and nearly 14% had at least one lesion on the mandible (lower jaw), McGreevy said. These lesions included exostoses (bone thickening) and concavities (bone thinning). Many horses had both an exostosis and a concavity, often with the lesions sitting adjacent to one another. For example, the horse might have a dip across the bone with a thickened line of bone beside it.
However, it’s important to note that many of these issues weren’t visible from simply looking at the horse, McGreevy added. Palpating the bone can give some information, but radiography helps confirm suspicions of such changes and rule out the normal “dishes” in the typical profile of many Arabian bloodlines. Although some people believe white hairs to be indicative of bony lesions under the skin, McGreevy said his team found no such correlations with the absence or presence of white hairs.
Many people might not notice lesions because these subtle deformities have become “the new normal,” he said. “We have to face the prospect that we might see so many of these horses every day that we’ve just become used to these pathologies,” he told The Horse. “And that’s a desperately sad prospect.”
McGreevy said his team didn’t investigate causes or risk factors for these lesions, so it’s not possible to say that certain kinds of nosebands, riding styles, or levels of tightness were responsible for various lesions. However, he said they have planned further studies to examine those factors’ possible roles.
The researchers would also like to investigate groups of horses used in other disciplines and sports in other parts of the world, he added.
“We’re very grateful to the Mexican cavalry for their transparency, which will go a long way in helping horses,” McGreevy said.