It's not going to have the full complement of vitamin content that it oughta.
Personally I would not use it for chicks. If it is unmedicated, and *if* (big if) the contents are not at all dusty, rancid, mildewy, mushroomy or any other wise "off" smelling, you might gradually mix it into whatever you're feeding your grown chickens, just a bit at a time, to use it up.
If there's any doubt, it's a good addition to the compost pile, with suitable carbon added (would be good in combination with coop cleanings, which because of the bedding tend to be somewhat carbon-biased).
JMHO,
Pat