There's millions of flight holes, the oak seems to be holding up to it but the loft/upstairs (upladder?) floor looks like pine and it's finished (and covered with hay - treacherous)
I'm not sure what sort of sealant is available here, I'm told sod all but, as I've been told lots of rubbish in the past, I'd better check. Not sure how good the concrete floor is in the pigsty but the previous owner chainsawed a big hole in the other end to drive his tractor in, which promptly sank through the floor.
The main rot seems to be near ground level



Above the pigsty seems a bit weak too, as it's single course.

Below that the walls are a foot thick (pig door:)


Btw I've found the key!

Which would still work if the door hadn't dropped...