I have no clue why this is happening, but this occurs to me since I swapped out my mod collection for a full medieval run.
They won't simply take the food from the object, but will take them as usual when on ground or on vanilla stockpile.

There were no errors to come up with, no important yellow logs, nothing which would hint anything wrong with that object.

https://i.imgur.com/cFQ2zQI.png

An example, chicken ignoring the Feed Trough completely and munching on the stockpile next to it. It came from south.