i have just moved my 5 week old chicks into a run inside my barn which has a concrete floor have put down straw and also put in the bottom part of their brooder is straw ok
As long as you DO NOT USE cedar you are good with almost any wood shavings/chips. I preffer shavings because of their larger size. If you use small wood chips watch out to see they aren't eating them. a lil scratching pecking is fine, but out right eating them is bad!!!