Sedation's Impact on Horses' Movement Patterns

Sedation's Impact on Horses' Movement Patterns

Researchers determined administering 0.3 mg/kg of xylazine had no significant effects on how the horses moved.

Photo: Kevin Thompson/The Horse

It might be easy to tell when a horse is noticeably lame, but finding the source of his pain isn’t always so simple.

“Horses are not able to tell us the region of pain, and sometimes there are no obvious signs of where the pain is coming from,” said Matthias Rettig, DVM, an equine veterinary surgeon at the Free University of Berlin, in Germany.

Veterinarians can use diagnostic analgesia (commonly known as nerve blocks) to help localize a lameness to a certain area. With this procedure, they desensitize the nerves in different areas of the horse’s leg, starting at the hoof and working slowly up the limb via carefully placed injections. Once a block is administered and takes effect, the veterinarians observes the horse trot. If a horse appears sound after a region is blocked, the practitioner evaluates that area as a potential pain source.

While nerve blocks are useful and effective in many cases, administering the analgesia can be challenging, especially in uncooperative horses.

“To desensitize the nerves, a local anesthetic is injected through a small needle around the nerve,” Rettig explained. “Some horses get aggressive during the procedure and kick, which can be very dangerous for the veterinarian performing the block.”

A low-dose of a sedative could help quiet a fractious horse, but how much of an impact will that product have on how the horse moves? Previous research results suggest sedatives can have an analgesic effect and interfere with the lameness when administered, so Rettig and colleagues set out to test the effectiveness and influence of a sedative (xylazine administered at 0.3 mg/kg body weight) on 44 horses. “This was a small study, but gives us something we can work with,” he said.

The team used an objective body-mounted inertial sensor system to determine whether the sedative impacted each horse’s lameness, and they ultimately determined that the drug administered at 0.3 mg/kg had no significant effects on how the horses moved.

Rettig cautioned, however, that doses should be chosen carefully, as too high a dose could skew the results.

“This effect may not be as worrisome in a horse that is really lame (Grade 3 or 4 out of 5), but if you have a low grade lameness (Grade 1 or 2 out of 5), the xylazine might cause a change in the lameness pattern and influence the veterinarian’s evaluation,” he warned.

Additionally, Rettig encouraged practitioners to use caution when working with difficult horses: “The veterinarian has to use common sense,” he said. “If the horse is too dangerous and the veterinarian is putting him/herself or anybody involved at risk, I suggest other diagnostic modalities to evaluate the cause of lameness.”

The study, “Effect of sedation on fore-and hindlimb lameness evaluation using body-mounted inertial sensors,” will appear in an upcoming issue of the Equine Veterinary Journal

About the Author

Katie Navarra

Katie Navarra has worked as a freelance writer since 2001. A lifelong horse lover, she owns and enjoys competing a dun Quarter Horse mare.

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