Moving horses from place to place is recorded to occur as far back in history as 3,500 years. At that time, horses were transported by sea and either were confined in boxes to the bowels of the boat or placed in slings on the deck of the boat. Even then, it was noted that transport was a stressful event that came with inherent health risks, and with a high mortality rate in horses shipped below deck. (Boats of that time were assumed to have extremely poor ventilation below deck.) It was noted that horses shipped on the deck, in the open air, survived the journey better than those below deck. In addition, it appears that the first reported research regarding horse transport was performed by General William Carter of the United States Army Veterinary Corps. Carter, who was in charge of transporting the Army’s horses to the Philippines by sea in the early 1900s, experimented with various methods of tethering. Carter’s studies led to the discontinued use of slings for the support of horses in transit. There is an excellent series of drawings depicting the early sea-transport of horses on display in the museum at the Kentucky Horse Park in Lexington, Ky. [links]