I know this has been requested, but who's gonna stop me, the mods?
Barns are single-story constructions, something like 6x5, with a 6x5 interior. They require 60 boards, 20 logs, and 80 straw. Primary boards affect the exterior wall color, secondary affect the exterior roof color, primary blocks affect the door color, secondary blocks affect the frame colors, Straw is just for the floor inside. You cannot build most things inside, like cupboards, because of the soft floor; but objects placed inside will not decay like any other building. Inside, you can construct things like hitching posts, fences, and a new object: Hay bale, 2x3.
The hay bale is made with 50 straw + 100 wheat/barley seeds, and when placed will act as a grass whenever the food trough is empty. Radius is about half of a food trough. It will temporarily act as q10 grass for your pregnant mares, so as to not give any benefit for breeding, but your other animals will not lose quality from eating it while it is in range. One hay bale can feed all animals in range for 3 real-life days, after which it will be depleted/gone, however the timer does not start until the animals start eating it. How many days left is visually represented by the size of the hay bale pile, kind of like a stockpile.
Interacting with the hopper inside of the barn will give you access to a swill container like the trough, but inside you can fit 1000L of swill instead of 200. Animals inside the barn will eat from this until it is empty, thus It acts as a sort of cistern for swill
The idea being that you can take like a week or two off of haven without even worrying about your animal quality. It lets players who stop playing have something to maybe come back for, instead of dead/lowq animals, and makes cave ranching more viable (Supports playstyle variety), not even to mention the larp possibilities. This hurts literally nobody, so I expect this to be patched in before christmas