At the 2022 AAEP Convention in San Antonio, Erin Contino, DVM, MS, DACVSAR, and Phoebe Smith, DVM, DACVIM, hosted a table topic on dealing with poor performance issues in horses.
Separate Pain from Behavior
Contino emphasized the importance of separating pain and behavioral issues. She stressed that, in most cases, a horse isn’t being naughty just to be naughty but rather acting out in an attempt to communicate that something is wrong. Just because an owner or veterinarian can’t find the source of discomfort doesn’t mean it isn’t there. About 50% of lameness in horses goes unrecognized by their trainers and riders, she said. At FEI competitions, the use of objective lameness measurements with the Lameness Locator along with subjective evaluation identified that 90% of the horses were Grade 1 to 1.5 (AAEP scale of 0-5) degrees of lameness.
Lameness Examination
A lameness exam begins with a thorough physical exam and palpation, including exercise on different surfaces with and without a rider, when possible. Contino advised gathering a complete history from the owner about the duration and frequency of the issues of concern. If lameness is identified, then it is appropriate to pursue diagnostic testing and imaging. If the horse is not lame, then she advised trying to recreate the issue. For example, have the rider mounted and ask for specific movements.
She remarked that foot pain and hind limb suspensory disease don’t always present as lame but may alter behavior. Diagnostic nerve blocks of the feet are a reasonable starting point. In cases without overt lameness, Contino starts with bilateral nerve blocks at the same time as, for example, an abaxial nerve block of both limbs. With regional anesthesia in place, have the rider mount up and see if they can feel any difference as they ride. If so, then one can follow-up with radiographs and ultrasound.
In situations where a horse has been seen by multiple veterinarians, it is important to have all steps documented in writing or digitally to avoid duplication.
Fitness Testing
Contino also finds it important to inquire if a horse is asked to do something it cannot do. Fitness testing might be relevant. A horse that is unfit for what is asked in competition beyond what he was prepared for might demonstrate behavioral changes and/or fatigue. A horse unfit for the task might demonstrate higher heart rates and higher lactate levels. A heart rate monitor is an excellent adjunctive tool for assessing heart rate and recovery during and following exercise. Overtraining is another element that causes a horse to act out from fatigue and soreness. Contino added that providing a horse with a variety of athletic efforts—cross-training—helps with both soundness and a horse’s mental state.
Poor Performance in Sound Horses
While many horses are lame, that might not always be the definitive cause of poor performance. Smith pointed out that musculoskeletal pain affects internal structures such as cardiac or respiratory components. She noted that gastrointestinal problems can be a source of discomfort, so endoscopic exam of the stomach has value, especially for comparison before and after competition. Persistent pain and stress can create gastric ulcer disease (GUS). She counseled that husbandry plays an important role in preventing gastrointestinal upset—horses need time out and opportunities to socialize. At the very least, she suggested turning two horses out together. Use of ground-based slow feeders provides more continuous food intake to buffer stomach acids. It is best not to keep a horse on proton pump inhibitors indefinitely as it alters the microbiome; rather, she recommends other long-term oral nutraceutical supplementation products, like Outlast or Relive.
Importance of Lifestyle and Management Changes
In all cases, Smith feels that it’s better to implement lifestyle and management changes rather than rely on nutraceuticals or pharmaceuticals. Some horses fare better with a competition schedule of only one week away from home rather than two. Blood glucose levels usually return to normal within two weeks following performance and travel, but not in all cases, so monitor glucose, she said. Checking on vitamin E levels is informational to identify deficits in green grass accessibility that cause sore muscles and general malaise.
Back Pain as a Cause of Poor Performance in Horses
Contino finds that back pain causes behavioral issues far more than anything else. In her experience, limb lameness and behavior are not well correlated whereas a problem with the axial skeleton is something a horse cannot “get away” from. A sound horse that is stiff or braced with bridle contact should have the axial skeleton examined. In addition, it is critical to evaluate saddle fit including with the rider up. In some cases, a horse might perform better without a whip, without a bit, or without spurs.
When attempting to identify if pain is an inciting cause, Contino recommended changing only one thing at a time. Tack, rider and riding environment should stay the same during such a trial. A trial of phenylbutazone treatment can help identify if pain is an issue, assuming gastric ulcers are not a concern. She noted that prednisolone (1 mg/kg) is more effective than NSAIDs at treating axial pain, again assuming no GUS concern.
Other Causes of Poor Performance
Other ailments to check for with regards to poor performance include:
- Selenium deficiency
- Polysaccharide storage myopathy (PSSM)
- Lyme disease, especially for horses living in or traveling to endemic states
- Equine protozoal myelitis, especially for horses living in or traveling to endemic states
Myofibrillar myopathy is usually not associated with elevated muscle enzymes or sore muscles.
