Medicated chick feed or organic?

I did both, started with medicated and started gradually mixing in organic after the first month or so. I think the medicated feed is important so they can get immunity to cocci without getting overwhelmed - and it can be really tough to keep food/water completely poop-free in a brooder!

I get a soy-free organic feed now, it has a ton of different stuff in it (fish meal and dehydrated egg for protein) and my chickens seem to be enjoying it a lot more than the medicated. It bothers me that virtually all of the conventional corn and soybeans in the US are genetically modified to withstand frequent treatments with RoundUp,  It seems like a lot of the conventional feeds i.e. Purina are promoting themselves as being vegetarian, but the more I read the more I'm not so sure that's a good thing. I don't think it's good for any omnivore (chickens or humans) to get all their protein from one source. That said, I was willing to buy a couple bags of Start & Grow and would do it next time I raise chicks (unless there's a way to make your own organic medicated feed with Corid?)

I have given my chicks unmedicated feed (though I have ordered vaccinated chicks) and they have been very healthy - I've never lost a chick or a chicken to any illness.  I have some 4 week old chicks now that my broody hatched, so they are not vaccinated, and I started them on organic feed from the get go - they are also very healthy, and have been out with my flock since they were less than a week old.  It may be that natural exposure to the flock, the dirt in their run - to  common organisms - enhances immunity in chicks as it seems to in young humans, also.  My experience is anecdotal, of course, but I've found it unnecessary to give medicated feed.

We start our chicks on nonmedicated feed from the day we bring them home.  We switched to organic shortly after bringing home the first set and they have stayed healthy.  The original batch had a little bit of problem with pasty butt, as did a couple we got from another chicken owner, but we mix in powdered probiotic (i can give doses if needed) and powdered kelp with their feed and not a single health problem (except one, and hers was a genetic issue).  So, go organic, go nonmedicated, but use some natural supplementation to go with it

I agree, again with my anecdotal experience.  Every group of chicks I have had on medicated feed and then put out at about 4 weeks all ended up with cocci.  For this most recent group I am actually switching to organic and keeping a VERY watchful eye and I have Corid on hand for the first sign of bloody poop.

With ours, we started with one tablespoon of probiotic sprinkled over the top of the feed once a day for a full week.  then we cut back to once a week.  Now, we just pour a small amount into the container we use to take the feed to the chicks, and shake it well to let it mix before putting it into their feed.  As far as the kelp goes, we just sprinkle some on top of their feed after its in the container or mix it in with the probiotic and feed before giving it to them, either way they enjoy it.  If fact, if the older ones see me putting it on the top they mob the feed trough!   Once we get the newest batch of organic feed next weekend, I'll premix the probiotic and kelp and put it into the feed right away, that way it is in there.  If I figured the ratio's out right I will need roughly four  pounds of the kelp and half a pound of the probiotic to mix in with the 300#s of grower we are getting.  And, to answer your other question, as long as it is stored correctly it can be kept for a while, just remember that once anything is processed it will start losing nutrional value.  We get the 300#'s because we only get it every 6-8 weeks or so. 
Any other questions I know I'm not the only person (and definitly not the most qualified since we just started chicken raising this year) but I do have my SO's Vitamin Cottage experience to draw on!
Best of Luck!

ETA: I wouldn't use the Mareks Vaccination simply because I've seen what other vaccinations can do.  I figure I'll let my chooks sort out whether they are going to get sick or not and then deal with it at that time   However, I do believe that not using a static run (one that gets denuded of all plant life and turns into a barren wasteland) is a good way to keep diseases at bay.  Or, if the static run is your only option, toss in hay, straw, leaves, grass clippings, produce trimmings from the grocery store, essentially turn it into a compost pile of sorts.  The chooks will keep it turned and such for you, will eat the bugs, and incorporate their own droppings into it.  Of course, don't throw in more than they can handle, obviously 20 can handle more than 3!  And, if managed right, there shouldn't be any smell to bother the neighbors and you can share it with them come time to compost the ground!

Actually, we get it from the natural health food store   It's also where I get the kelp from, although I'll probably order that online for the larger quantity.  You want to get the stuff that has the highest concentration of bacteria per serving.  yogurt is actually ok, just in small amounts, plain yogurt and preferably not the lite or diet stuff.  organic would probably be even better.  if you go to the feed store there is a product called Probios that you could probably use, but since we get the discount at his store, we just do that

And you ain't annoyin!  the whole point of this forum is to ask questions, give answers, and enjoy chickens together!