I always used to haul cattle tied but then a friend told me a story about a guy he knew who got in a wreck with a load of horses. The truck & trailer rolled and he couldn't get out to free the horses. Only one horse survived and it was because his halter snapped. The rest were strangled or had their necks broken because they were tied up. Definitely not saying they can't die when they're not tied but after hearing that story I haul my animals loose when possible.