The size and amount of livestock you need to haul is the most significant factor. Do not purchase a cattle trailer insert for larger animals, like horses or cattle, less than 16 feet long. For smaller animals like sheep, goats, and pigs, a 12-foot trailer will fit your needs. However, if you are hauling many smaller animals, you will need a 16-foot trailer. Learn more about the capacity of your livestock and the size of the cattle trailer you need.