I think every medication or medicated food should have a withdraw time on the label

. Of course they dont. Here is what I found in the Chicken Health Handbook; refering to feed medicated for prevention of cocci, "The medication has a withdraw time of 30 days, so if you raise meat birds, you'll have to find a non-medicated feed during the last month"
Since broilers are ment to be eatten I would think the feed store would have a non-medicated feed to offer
Hope this helps.
Bill