I know that I will be set straight by many who will say, "That's what they eat when mama raises them," or words to that effect, but we also used to put leaches on our butts to cure fevers. Science doesn't always beat nature, but sometimes it does. I like the fact that I can feed my new chicks a pretty ideal mix of the nutrients they need at this stage without the guess work and chance involved in letting them range free. There will be plenty of time for that, and I am okay with supplementing with some greens and other treats, but not before they've had a good go at the commercial feed.
Plus, I don't have a variety of wild things in my suburban neighborhood of St. Augustine grass and decorative shrubs. If I had an acre or two of wild grass, wild flowers and lots of bugs, I would probably feel differently, but for this backyard (very literal in my case) chicken farmer, commercial feed is the way to go for the little ones.
UGCM