Safe to haul what? a horse?, a cow? sheep, goats? If you mean is your truck the right size to haul the trailer and 2000# of horses then yes according to the 7,000 towing capacity.
More generic stuff..... YES your truck is rated to do it.... but as has been mentioned already, do the brakes work?, lights?, have you inspected the springs, mounts, frame, tires, wheels, bearings??///