any domesticated animal used in drawing heavy loads. Draft animals were in common use in Mesopotamia before 3000 BC for farm work and for pulling wheeled vehicles. Their use spread to the rest of the world over the following 2,500 years. While cattle, usually in teams, have been used most often as draft animals, horses and donkeys have supplanted them in many areas. Some horses-such as the Belgian horse, the Clydesdale, the Suffolk, the Shire, and the Percheron-have been bred to serve as draft animals; they weigh more than 725 kg (1,600 pounds) and stand at least 16 hands high. The Asian water buffalo, however, is probably the most important draft animal in the world today. Many of the some 165 million domesticated water buffalo worldwide are used as draft animals, particularly in tropical Asia, where they assist in the production of rice. The role of draft animals in agriculture in less-developed regions of the world continues because of the advantages they offer: their feed is easily grown and commonly available; little maintenance of the animals is required; their manure is a valuable resource for the farmer; and the animal itself may become a source of food or other products at the end of its useful life.