Guide to Feed Chickens
The easiest way of feeding animals is to let them wander and eat wild grasses. Grasses die in winter, so you need to start feeding them then.
If you build in an area with no grass nearby, or cut all the nearby grass, you will need to start feeding them immediately.
Chickens will eat cut grass (preferably hay) and any grain (If they are hungry enough they will eat almost any other kind of food as well).
The easiest way to feed them is with the hay trough and grain trough. Unlock path:
Iron nails -> water dipper -> water trough.
If you don’t have the troughs yet, you can place a stockpile, or a haystack or grain pallet, somewhere where they can get at it, and make sure it stays filled.
Also note that your animals need access to water.
I would suggest not locking them in a pen until you have the water trough.
Alternately, you can build a pen around a small lake, but in winter you will still want the trough.