Re: "They ship livestock in..." [the cargo hold of aircraft]
What if the cattle herd wandered to one end of the fuselage? Might throw off the balance.
That reminds me of a very nerdy joke one our University lecturers used to like to tell in his Control Systems lectures. The punch line was "The plane crashed because all the poles were in the right hand side of the plane"
A virtual pint for anyone who understands that!