Q:My 24-year-old Arab gelding recently came off the trailer very sweaty and with tremors in his shoulder muscle and hindquarters. It was only a 15-minute trailer ride, and it was sunny, but not hot. He walked normally and seemed bright and alert. We had trail ridden two days in a row, and I thought, perhaps, it was muscle fatigue. The previous day, when he had no problem, had been cooler and overcast, but it was a much longer trailer ride. The other three horses in the trailer on both days seemed okay, although one was somewhat sweaty.

Yesterday he was trailered 50 minutes with road delays, and it was sunny and 75-80°F. He had not been ridden for four days, so he was not fatigued. He arrived very sweaty again and with the same kind of tremors. He drank before we left. I gave him half a tube of electrolytes, and when he seemed okay we went on our trail ride. He appeared fine and energetic. He drank before boarding the trailer for home, and I gave him the other half of the electrolyte paste. He was in the same condition as on the previous occasions when we got home. I checked on him later and he was dry and eating well, perfectly content.

I can't figure out what is happening to him. Is he suffering from heat issues because of his age?          


A:It is significant that the muscle tremors and sweating your horse experienced during and following a trailer ride resolved quickly and uneventfully. If your horse is affected enough by electrolyte imbalances to elicit muscular tremors, he isn't likely to act completely normal as you described or be in condition to continue on a trail ride. His condition upon arrival could be related to the trailering event, rather than solely to the weather or duration in the trailer. It is thought that muscular effort required by a horse to balance in a moving trailer is comparable to him having walked the whole way. High ambient heat could add to his discomfort and sweating, but it might not be the direct cause of the muscle tremors. A 15-minute trailer ride won't induce sufficient sweating to create electrolyte disturbances or significant dehydration; you'd need many hours in the trailer under high heat and humidity conditions to elicit such adverse effects. To check for electrolyte-related muscle disturbances, it would be helpful to have your veterinarian perform a thorough physical exam on your horse and run a chemistry panel on him at the time he is exhibiting muscle tremors.

In considering heat inside the trailer, you can check a few things. Place a thermometer near your horse to see how hot it really is. Install rubber floor mats and bed with shavings--these provide some relief from road vibration and insulate the floor from road heat. A trailer with an insulated top also doesn't get as warm inside as one without insulation. Open windows and side panels when possible, and install battery-operated fans within the trailer to improve air circulation.

To sort out if trailer-specific problems are causing anxiety, try a few hauling changes: load your horse in a different location within your trailer, haul him in a different trailer, load him with different horses, load him so he is able to turn around at will, and drive on roads without a lot of stops and starts or windy turns. See if any of these altered situations change the dynamics of how he is at the end of the journey. You could also install a video camera in the trailer to observe your horse's behavior while in transit. You could ride in the empty trailer to see how he hauls, but check your state legal statutes before trying this.

It is not uncommon for trailers to develop suspension problems from normal wear and tear. Have your mechanic check ball joints and suspension parts to ensure the trailer has as little vibration as possible, and check that your hitch and receiver have minimal wiggle as the trailer is pulled down the road. Horses are sensitive to environmental influences, such as trailer vibrations. What might go unnoticed by one horse can create anxiety in another.

About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her recent book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care (available at Shop.TheHorse.com or by calling 800/582-5604). She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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