I just avoided a complete disaster, my now near 20 years old fortress nearly died because of a single cage.
On this fortress i have decided to keep all the animals instead of killing/butchering most of them, and as usual to avoid some possible framerate problem with animals doing something buggy with their pathfinding, i make a cage, build it at some place in the fortress and put every single of the animals inside (as a single cage can contain infinite amount of them).
The difference with past fortress is that i left a very lot of animals alive and put them all in the cage instead of only keeping a few, and that is probably why i never noticed this before.
Years later , i started to notice several messages spamming about being unable to bring food to a wounded dwarf (as we just killed a hundred of elves, one of them managed to still get inside the fortress and hurt a dwarf before being taken out).
I checked if someone wasn't stuck on a tree or if by any bad luck i had somehow wrongly defined a burrow , but no everything was correct .
While looking around i noticed the farm was empty of anything growing.
Huh ? it had worked for so many years and fed the whole populace all that time without a problem.
I checked my stock and i still had several hundred of plump helmet spawns and all the farmers were still alive and kicking, and the stock had mention of 0 food ! so i had no idea what the hell was going on, why those farmers weren't growing anymore plump helmet for food.
My fortress was going to see dwarves dying from famine soon.
Until i checked the cage that just got an animal dying inside of it as i was thinking of probably butchering a lot of them to get food.
... All those hundred of plump helmet spawns were inside of it ! And after checking the internet looks like it's one of DF known bugs, as when your dwarves bring plump helmets to animals , a seed is left behind but unlike for dwarves nutrition, that seed is left inside the cage forever, the dwarves NEVER try to bring it back to the stockpiles or use it in the farm.
From the stocks i marked all the plump helmet spawn to dump , and only then all the dwarves went to collect them , after that i marked them all for "undump" and the farmers went to immediately use them on the farm.
I was a bit anxious as it took time to grow the new plump helmet into food, but fortunately when it happened the dwarves were still all alive, they rushed to the stockpile to eat them though
Lesson learned for next time , time for a lot of animal butchering.