Horses can suffer heat stress and dehydration when transported in hot weather, especially if humidity is high — which makes it more difficult to cool themselves by sweating. There are ways a person can minimize stress and fluid loss, however, with careful management before, during and after a trailer trip.
Carey Williams, PhD, equine extension specialist and professor at Rutgers University, said the important thing to remember is that when horses are being hauled, their muscles are working all the time. They are constantly moving, shifting weight and keeping their balance in a moving trailer.