The first time Tonka collapsed, it was almost kind of funny. The palomino Quarter Horse was standing at the in-gate, with his owner Judy in the saddle, waiting for the last class of a weekend show. Quiet but ready to go, Tonka, age 15, looked like the seasoned veteran of the show circuit that he was.
Then it happened. If anyone had been watching, they would have noticed gelding’s head drop ever-so slightly. But no one could have missed what came next: Tonka’s front knees buckled, and he toppled muzzle-first into the dirt. He instantly scrambled back to his feet, looking almost embarrassed.
Judy, luckily, stayed in the saddle. “Oh, are we boring you, Tonka?” she laughed as she patted her unflappable gelding on the neck. “Try to focus, buddy. We’re almost done.” The remainder of the day passed uneventfully. Judy and Tonka earned a third-place ribbon in that last class and, later, the gelding grazed happily as Judy dismantled the show stall and packed up the trailer for the long trip home.
The second time Tonka collapsed, Judy became concerned. It was on the final afternoon of another three-day show. This time, Judy was on the ground, having led Tonka to the show office to retrieve her overnight stabling invoice. While she waited for her paperwork, Judy held Tonka’s reins and chatted with a friend. “I had no warning—one minute he was standing there, quiet as can be, and the next minute, he was on the ground,” Judy told the on-site veterinarian who looked Tonka over. Once again, the gelding got back up immediately, and besides a slightly scraped knee, he had no obvious injuries. Judy called Tonka’s regular veterinarian to schedule a full examination for the gelding when they got home.
Two weeks later, Judy told her veterinarian what she knew. Tonka had never collapsed at home, only at shows. And the episodes seemed to come out of nowhere. The gelding showed no signs of illness or discomfort beforehand and had been competing successfully in classes in the preceding days. Before each collapse, Tonka had been standing still—he hadn’t stumbled or been pushed off balance. He always recovered quickly and seemed perfectly normal afterward.
The veterinarian checked Tonka’s vital signs—heart rate, blood pressure, respiratory rate, temperature—and found them to be in the normal range. He also performed a series of tests to check gelding for neurological impairment but found no signs of trouble. Finally, the veterinarian did a lameness exam, noting that the gelding had some moderate stiffness in his hocks despite receiving a joint support supplement and the occasional dose of anti-inflammatory medication. The veterinarian drew blood for analysis but told Judy he’d be surprised if it revealed anything abnormal.
Judy was both relieved and frustrated. “Why would a seemingly healthy horse collapse out of the blue when he’s not even being asked to move?” she asked.
“I have a theory,” the veterinarian replied, “but it may take some time to test it out.”
Technically known as upward fixation of the patella, sticking stifles occurs when the medial patellar ligament of the stifle becomes hooked on the end of the femur. When a stifle is “stuck,” the horse cannot flex the joint or advance the limb. The leg usually becomes unlocked when it is flexed, often with a jerky motion. Mildly affected horses are usually safe to ride, but more severe cases of sticky stifles can interfere with a horse’s gaits, performance and stability. (Adobe Stock)
A flavivirus carried by birds and spread by mosquitoes, West Nile Virus (WNV) causes the disease known as West Nile encephalomyelitis. Most horses bitten by mosquitoes carrying WNV will show few, if any, signs of any illness. However, in roughly 10 percent of cases, WNV crosses the blood-brain barrier to infect the central nervous system. In those cases, within five to 15 days horses will begin to show a number of more serious signs of illness, including elevated fever, muscle weakness and incoordination, loss of appetite, behavioral changes and paralysis and recumbency
While horses can doze on their feet, they must lay down for deep, restorative sleep, also known as rapid-eye-movement (REM) sleep. If a horse goes days or weeks without REM sleep, he can develop signs of sleep deprivation, including increased daytime drowsiness, weight loss and poor performance. If a horse is deprived a sleep long enough, he may partially or completely collapse as his body slips suddenly slips into an REM state. (Adobe Stock)
Severe cramping of the large muscle masses—often in the loins and hindquarters—tying up can be either sporadic or chronic. A horse with tying up may have gait abnormalities and in more severe cases will be reluctant to move. Other signs include excessive sweating, rapid breathing and heart rate, and muscle tremors. (Adobe Stock)
Tonka’s veterinarian suspected that sleep deprivation was the cause of Tonka’s mysterious collapses. He explained that there are three distinct phases to sleep: A deep, restful phase where the horse is relaxed but easily roused; slow-wave sleep in which the horse is even more relaxed but his brain waves are slow and large; and paradoxical sleep, also known as rapid-eye-movement (REM) sleep, during which the horse loses muscle tone and reflexes, but has increased brain activity. For true REM sleep a horse needs to be comfortable enough, physically and mentally, to lie down.
While humans need two or three hours of REM sleep per day, for horses, 30 to 60 minutes of REM sleep will suffice. Like people, horses can cope with insufficient REM sleep for a while. But eventually sleep deprivation catches up with a horse and he has a “sleep attack”—suddenly losing consciousness, entering REM asleep and waking up as he hits the ground. This can happen at any time—in the field, under saddle or in the barn aisle. Some horses can go as long as 14 days with insufficient REM sleep without ill effects, others can only go a few days.
Tonka did have a touch of arthritis in his hocks, which could, theoretically, hamper REM sleep by preventing the gelding from lying down. The biggest clue, however, was the fact that the gelding’s sleep attacks occurred only on overnight road trips. A variety of conditions at the show grounds could be contributing to Tonka’s sleep deprivation on the road, the veterinarian said. These included noise, social anxiety and/or even exposure to security lights left on all night. He and Judy brainstormed ways to improve Tonka’s sleep while away from home.
Based on her veterinarian’s suggestions, Judy made several changes to Tonka’s management and accommodations at overnight shows. For starters, she began requesting stalls at the far end of the barn, at a distance from hubs of activity. This meant longer walks for her but quieter surroundings for Tonka.
She also convinced her daughter–whose horse was Tonka’s pasture buddy at home—to come to a few shows. The hope was that with his pal in the next stall, Tonka would relax and feel secure enough to lie down for REM sleep.
Judy also bought some new gear: ear nets that held cotton balls in Tonka’s ears to dampen noise and a eye mask designed to increase the wearer’s natural melatonin levels and promote better sleep by blocking blue light.
Judy’s daughter joked about Tonka’s elaborate “bedtime routine” and gear. But each morning, they arrived to find the gelding covered in shavings from having a good night’s sleep. The new routine was working. Now able to achieve REM sleep even away from home, Tonka completed the show season without another sleep attack.
