“It’s important to educate riders and trainers in visual lameness assessment to detect changes in their horses´ motion symmetry (early),” said Marie Rhodin, PhD, of the Swedish University of Agricultural Sciences, in Uppsala.
Rhodin and her fellow researchers invited horse owners across Sweden to participate in their study if they considered their horses healthy and sound and rode them at least two to three times a week. The scientists accepted 222 horses into the study, and they traveled to each horse’s home site to carry out inertial measurement unit (IMU) analyses of his movement at a trot on a hard surface.
They found that 161 of the 222 horses (72.5%) had measurements that exceeded established threshold values for lameness, Rhodin said. It’s possible that this could reflect biomechanical variations that aren’t actually painful, but it’s also possible that the horse is in pain, she said.
“We don´t know whether all asymmetries seen in these horses are related to pain or not, and I think it is important to try to rule that out before thinking of motion asymmetries not related to pain,” she said. “Due to the very high number of horses with motion asymmetries, this raises the question of other causes such as inherent motor laterality or conformational asymmetries, but we need to do more research to answer this question.”
Still, for certain study horses, there was little room for doubt. “Some of the horses were very lame, and it was surprising how that could be undetected by riders and trainers,” Rhodin said. In some cases, the rider’s riding style might have masked the asymmetry, as it would have been perceived by a trainer or other observers, she added.
But regardless of the horse’s current pain level, nonpainful asymmetry could lead to pain over time, Rhodin said. “Movement asymmetries are associated with differences in limb loading and propulsion which may, over the long term, lead to injuries,” she said.
Familiarity with facial expressions in ridden horses can help riders and trainers detect signs of pain, which could accompany asymmetry, and stress, Rhodin said. Meanwhile, scientists need to dig further into understanding the consequences of asymmetry in horses.
“I think this is a very important topic for future research, and, from an animal welfare perspective, we need to improve our knowledge and skills to detect early signs of pain and discomfort in our horses,” she said. “Research on associations between motion asymmetries and pain behavior such as changes in posture or facial expressions in horses suffering from acute and chronic orthopedic pain may help as answering these questions.”
The study, “Head and pelvic movement asymmetries at trot in riding horses in training and perceived as free from lameness by the owner,” was published in PLoS One.