A donkey can safely carry up to 20 percent of its body weight, if the load is properly balanced and secured. The average standard donkey weighs approximately 500 pounds and therefore can carry up to 100 pounds of cargo. Miniature donkeys, averaging under 400 pounds, can pack smaller loads.
A donkey should be allowed to mature fully - between 3 and 4 years of age, depending on the breed and individual - before being used as a pack animal. Waiting until the donkey is full grown before beginning heavy work generally leads to a longer working life and reduced chance of injury.