We used wood chips in our chicken tractor for a couple years. We really liked it, but it would get expensive for the large area I have to cover now.
Might look around for someone that has a saw mill my neighbor does and is glad for me to come get saw dust from him. He's glad to get rid of the head-ache of having to move it and pile it up himself. I get it by the truck load at a time but now have a trailer with tall sideboards and will park it underneath the spout and fill it up over a duration of time and pull it home with a tractor cover it and use as needed, saves a lot of SHOVELING that way.
Jeff