A large animal that's used to help carry goods is known as a packhorse. In the 19th century, North American gold prospectors used packhorses to carry their supplies over difficult terrain.
It may seem obvious that a packhorse is a type of horse (clearly, one that carries a pack loaded with goods) — in fact, you can also describe a mule, pony, or donkey as a packhorse. Most of these working animals haul supplies in bags that hang down along both sides of their bodies. Packhorses have played an important part through history, accompanying explorers, traders, and anyone without access to a vehicle or a paved road.