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