For several years now, researchers have studied various aspects of horse health and owner perception, hoping to understand — how good is the average owner, really, at noticing when something is wrong with a horse? A study published last month in the Journal of Equine Veterinary Science suggests that even experienced horse owners may not be all that good at detecting lameness in their horses, but that conclusion comes with quite a few caveats.
Horse owners in Switzerland were recruited for study participation by a survey where they were asked about their horse's soundness and their own ability to assess that soundness. Then, horses were jogged on a hard surface for a conventional lameness exam. They evaluated by two veterinarians specializing in orthopedics and had front, hind and overall lameness rated on a scale between zero and five, with five being the most severe. Horses then had their gaits analyzed digitally while they jogged on a treadmill. The gait analysis was intended to pick up on asymmetries in leg, head, pelvic, and spine movement as well as weight-bearing asymmetries. Veterinarians also watched horses on the treadmill and graded horses' lameness there, too.
Most of the owners participating in the study reported they had regularly attended informational events about equine topics, and had been riding for 25 years on average. Nearly 43 percent of them held a license with the Swiss Equestrian Sport Federation.
Researchers found that owners sometimes missed lamenesses detected by the veterinarians, and veterinarians sometimes came to different conclusions from gait analysis software — but the study's authors say the results aren't as straightforward as saying, “The computer is always right.”
While a quarter of owners reported occasional lameness in their horse, only half of those horses actually showed lameness above a two. On the other extreme, about half the horses owners considered sound were assessed by veterinarians having a lameness equal to or greater than 2/5. Two horses scored a 3/5. Researchers cautioned however that horses in the first group — those that owners thought had a soundness problem that didn't really manifest on examination — may have issues that become apparent only when the horse is ridden, which isn't part of the standard veterinary lameness exam. It's also worth noting that owners who correctly assessed their horse had a more serious soundness problem might not have been included in the study because their horses didn't meet age- or workload-related requirements for study participation.
Veterinarians scored 55 percent of horses as 2/5 lame or greater in their conventional exam, and 74 percent of horses as 2/5 lame or greater when watching them on the treadmill. Computer measurements of asymmetry found movement asymmetry in 57 percent of horses and weight-bearing asymmetry in 58 percent of horses.
While those numbers may sound high, study authors say the conclusion isn't as simple as assuming that the majority of the horse population is lame; owners were given the choice about whether to bring their horse in for veterinary examination, and again allowed to choose whether they wanted the horse to undergo gait analysis. This may have resulted in more horses with previous orthopedic problems being selected by their owners for further analysis.
It's also important to note that people simply don't see asymmetry all that easily. The study pointed to previous research which showed that at least 20 percent asymmetry between limbs is needed before even an experienced person will be able to visually identify it.
The study also raised questions about the sensitivity of digital gait analysis, which as become a popular tool in academic research.
“The definition of thresholds above which objectively measured movement asymmetries are classified as lameness needs careful consideration as it remains unclear to what extent asymmetries are related to pain, mechanical abnormalities, or laterality,” authors wrote. “This leads to potential welfare problems: if threshold values are too high, lame horses might go unnoticed, whereas low threshold values could result in many orthopedically healthy horses being categorized as lame. False-positive identification of lame limb(s) can have wide-ranging effects when the horse is subjected to unnecessary and expensive procedures, for example, nerve-block anesthesia or diagnostic imaging.”
Previous research has shown that subjective lameness analysis, like conventional lameness exams, aren't perfect either. If anything, authors conclude, the differences in owner, veterinary, and digital analysis of horses' movement may suggest that horses benefit most when more than one assessment is applied.
“With regard to animal welfare and to avoid misleading treatment, the highest priority of a lameness assessment should be to prevent false identification of the affected limb. Considering that the inter-rater reliability of equine veterinarians in subjective lameness evaluation is 76.6%, applying only one assessment method in mildly lame horses appears insufficient. Whenever possible, more than one diagnostic method should be applied to double check if the presumably affected limb is identified correctly, to minimize treatment errors.”
See the full study, which was part of a collaborative effort led by Dr. Jasmin Müller-Quirin at the University of Zurich, here.
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