When the bag runs out. It's recommended for minimum of 8 weeks. Many continue with it until pullets start laying. Some switch to grower feed when the starter runs out then to layer feed when the chickens are near laying or laying. It's your choice if when your current bag runs out if you purchase another or go to grower or if you've only 4 birds then will be about time for layer mix.
I cannot really get anything except medicated starter here so that's what I feed until they are ready for layer at around 16-18 weeks old, or when they are about ready to be part of the main flock. I could feed a game bird grower, but it's quite expensive and makes their poop smell really awful, LOL.
I wouldn't feed them medicated starter, let them build natural immunity so they aren't reliant on medication to keep them from getting sick, which I why I would also never use a wire bottom brooder. Thats just my opinion though, and I'm sure theres plenty of people who disagree. To me, the best coccidiostat, which is what most medicated feeds aim to do, is proper hygene for your chicks. Okay Im done with my soapbox now, sorry. Feeding chickens is not rocket science. If you feed them starter/grower fora little longer or a little less time then reccomended, its not going to hurt. Because I keep so few chicks at one time, I often have the same bag of starter for longer then their reccomended 16 weeks and I just give it to them until it's gone. I know some people who do not even use a chick starter and opt for a higher protein feed such as game bird from the start.
I don't use a medicated starter, I have been having really good luck with NON-MEDICATED Start and Grow (Purina). I leave them on it until they start to lay or around 18 weeks old.
I buy one of those small expensive bags of medicated chick starter, for their first feed. I figure they have gone from the hatchery, to the store, where they were handled etc, to my place all in less than a week. That medicated will help in case they are exposed to something during this time of great upheaval. When it is gone I switch over to non-medicated chick starter crumbles. Depending on when they run out I usually then move to a Flock Raiser type feed in pellet format. This is used when my birds are integrating in to the existing flock. This way the new birds and the old birds can eat the same chow. I just make sure that there is plenty of oyster shell around during that time. Once the first chick of the bunch starts laying I then only purchase Layer type pellets from there on out.
There really isn't any "medicine" in medicated starter the way most people think of it. It's just something that helps keep down the protozoa population a bit while the chick develops immunity naturally, Amiprolum (sp?).
My local coops recommend staying with the medicated chick starter for the first 8-12 weeks. With every flock I've raised there is intermittent diarrhea in chicks and the medicated feed is supposed to help prevent spread. I've not lost any chicks along the way so I I assume it helps correct the gut flora in the affected chicks. Please note, if you want to sell organic eggs, you cannot use mediated feed at any time, including the first few weeks of a chicks life.
I feed medicated chick starter until they are laying age and then I switch to layer feed, about 20 weeks of age.
