I'm new at raising baby chicks and so took some pointers from this forum and other things I've read when concocting my 31 little 4-week old chicks' latest treat. When I put them out in their temp run (on nice days until their coop is finished) I put out two bowls of roast (yes, you're reading this right) CHICKEN, lemon cucumbers from the garden, apples from the apple tree. I pureed this in a food processor and put it in two stainless mixing bowls, and it was devoured within 1 hour. They ate it like it was candy. They also love yogurt - but I did have to "peck" at it with my finger for a few seconds to get them to try it. Then, they couldn't stop eating it.
They don't seem to like celery so much, though.