Don't automatically assume you need to load your chicks up with antibiotics. One of the (many) reasons to raise your own chickens is to have a better quality meat that is also healthier than what you get from the store and the chicken factories. Don't replicate the procedures the disgusting chicken factories use. They load their birds up with antibiotics because they NEED to. Raise them right and it's totally unnecessary in most circumstances.
I agree, We use the antibiotics to prevent Coccidiosis. It is at very low levels in the feed, and we mix it 50/50 with normal feed until 8 weeks of age and then we use regular old feed. this was a tip from a fellow homesteader whom I trust a great deal. Other than that we do not medicate for anything else unless need be, no growth hormones etc. You hit the nail on the head with the disgusting practices of the chicken factories!