Whenever I see brand-new baby calves I think back to the bad old days when we still had to worry about screw worms. Every calf's navel cord was an attractant for the screw fly. We were reluctant to tag cattle's ears, or, back in the day, "mark" their ears, or to dehorn or castrate. Every open wound was an invitation to worms. We had a bull that got them in his hoof, and a horse that had them in his private (?). Treatment was gruesome but it usually worked.
I'm guessing that some of the younger cattlemen here never encountered that scourge. I've also wondered if the screw fly ranged up into the midwest and northwest cattle areas.