Evaluating the Equine Poor Performer

Veterinarians can learn a substantial amount about equine poor performers by watching them work in an exercise test.

Photo: Erica Larson, News Editor

The change might be subtle—a missed lead change here and there or a less significant extension. It could also be more noticeable—uneven gaits, rampant tail swishes, bucks, or other conflict behavior. Whatever the difference, it’s often easy to tell when your horse isn’t performing up to par. What’s sometimes not as simple, however, is determining why.

At the American Association of Equine Practitioners’ Focus on Poor Performance meeting, held Sept. 10-12 in Lexington, Kentucky, Elizabeth J. Davidson, DVM, Dipl. ACVS, ACVSMR, reviewed how veterinarians evaluate these horses and help them return to full function. Davidson is an associate professor of sports medicine at the New Bolton Center, the University of Pennsylvania School of Veterinary Medicine’s large animal hospital, in Kennett Square.

“Many body systems must be functioning properly for a horse to do what we ask of them on a daily basis,” Davidson said. And when one or more of those systems break down, the horse isn’t able to perform to his full potential.

In many cases, she said, affected horses’ performance decreases gradually, and they often don’t have any distinct clinical abnormalities. “For these horses, investigation into the cause(s) of poor performance can be a real challenge. This is where the real detective work begins.”

A veterinarian’s ultimate goal with a poorly performing horse is to return the patient to full function, which requires the appropriate treatment. Thus, he or she must first narrow the possible causes to get a good idea of where to start.

Davidson also stressed that not all abnormalities are equal. Their impact will depend on severity and what kind of work the horse does. For example, what could be a career-limiting respiratory ailment for a racehorse might have significantly less impact on a dressage horse, she said.

The Poor Performance Exam

Horses with obvious issues—a significant lameness or a noticeable respiratory condition, for example—are generally easy to diagnose. But most poor performers don’t have these overt signs of a problem.

For these horses, start with a thorough history. Davidson encouraged attendees to get a clear description of the complaint and how long the problem has been present. Also gather a detailed performance history and review any past illnesses, injuries, or surgeries. Veterinarians should ask whether the owner has tried to treat the presenting complaint and with what and whether the horse’s condition improved.

Once the veterinarian has obtained a history, he or she should conduct a physical exam. Davidson advised practitioners to note any obvious abnormalities, such as joint swelling or muscle atrophy at this point.

“The overall conformation of the horse, and in particular limb alignment and misalignment, should be noted,” she added. Further, the practitioner should examine the limbs for signs of heat or pain, particularly in the joints, flexor tendons, suspensory ligaments, and hooves.

Next, Davidson moves to a lameness exam, which is an important part of the process, as musculoskeletal issues are the most common cause of poor performance. She said one survey suggested that at least half of all equine operations have at least one lame horse, and virtually all horse facilities house unsound horses.

She cautioned that subtle lameness is often overlooked, and many affected horses can perform their job despite the injury. Thus, it’s important to conduct a lameness exam even if the owner doesn’t report lameness as the main issue.

During a lameness exam veterinarians can employ a variety of methods, from observing the horse exercising under tack to using diagnostic analgesia (nerve blocks), to localize the lameness.

And, Davidson encouraged attendees not to turn to imaging—such as radiographs, nuclear scintigraphy, computed tomography, and MRI—until completing a thorough lameness exam, but noted that it can help pinpoint the issue. Nuclear scintigraphy, she said, can be very useful when faced with a horse with inconsistent, subtle, or multiple-limb lameness to help identify problematic “hot spots.”

The second most common cause of poor performance is respiratory problems, so Davidson recommended conducting a respiratory exam. She said this exam, based upon the findings and a potential abnormality’s severity, can include external larynx palpation; thorax auscultation (listening with a stethoscope), with and without a rebreathing bag; and a resting and/or dynamic (during exercise) endoscopic exam.

Another important part of the process is a cardiovascular exam, Davidson said. In this exam, the practitioner will listen to the horse’s heart, noting any murmurs, dysrhythmias, or other abnormalities. If the veterinarian finds any abnormalities, he or she can conduct an echocardiographic exam (evaluating the heart via ultrasound) and/or electrocardiograph (commonly referred to as an ECG, which measures the heart’s electrical activity, or its rate and rhythm) to explore the horse’s heart further.

“Extended monitoring for 24 hours is especially indicated in the collapsing, fatigued, or ill-defined poor performer,” she relayed.

Other evaluations Davidson recommended, as needed, are a neurologic exam, an endocrine exam, and a metabolic exam.

Davidson also said veterinarians can learn a substantial amount about poor performers by watching them work in an exercise test, either in the field or on a treadmill. She said each has its pros and cons.

For instance, field testing allows the veterinarian to observe the horse in his normal work environment and conditions and with his normal rider. Additionally, she said, field testing modalities—such as dynamic endoscopes and mobile ECGs—have improved over the years. However, limitations can include environmental conditions (i.e., rain or snow) and rider or driver influence.

Meanwhile, treadmills provide an opportunity to collect controlled and repeatable data. But drawbacks include the lack of a rider, the treadmill’s surface, and the need to acclimatize the horse to the machine before testing can begin.

Now What?

As the veterinarian proceeds through the evaluation, he or she will take notes and narrow the possible causes for the horse’s poor performance. Sometimes the answer winds up being easy to decipher, while other times it’s a complex combination of issues.

The practitioner can then discuss treatment options with the owner and proceed with getting the horse back to business.

Take-Home Message

“Poor performers can be a diagnostic challenge that takes substantial time, effort, and money to get to the bottom of,” Davidson said. “But, you need to accurately identify the problem in order to implement an appropriate treatment and make the best decision for the horse.”

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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