Adding To Flock


In the Brooder
May 22, 2019
Hello, I have 5 pullets 12 weeks old and am going to add 2 others that are 14 weeks old. My current 5 have never been vaccinated and have been on medicated start and grow since day 1. The 2 new pullets have had vaccinations including coccidiosis, so my assumption is that I should stop using medicated feed and go to non-medicated feed until the 5 are 18 weeks then all go to layer feed. Am I on the right track? Sorry, I am new at this so any advice is greatly appreciated.


Dreaming of Spring Flowers
BYC Staff
Premium Feather Member
7 Years
Jul 16, 2015
I believe you are supposed to stop feeding medicated feed by 6-8 weeks if age, so I would stop it.

I personally never feed layer. I feed either an All Flock ration or a non medicated starter grower. I put out a separate bowl of oyster shells for the calcium needs.

If you still intend to switch to a layer I would not do it until all are laying as it's generally lower in protein and can slow maturity.


Premium Feather Member
14 Years
Feb 2, 2009
Southeast Louisiana
Am I on the right track? Sorry, I am new at this so any advice is greatly appreciated.

I don't use medicated feed but it can be a good tool if it is used properly. First, look at the label. What "medicine" is in the medicated feed you are using? In the US it is almost always Amprolium but there are a few exceptions. I don't know what the practices are in other countries. What I'm going to say only applies if it is Amprolium. If it is something else, then this will not apply.

Amprolium is not an antibiotic, it is a thiamine blocker. In the dosage in medicated feed it does not cure anything, it helps reduce the chances of your getting sick or dying from Coccidiosis. It does not totally prevent Coccidiosis, but it greatly helps. Coccidiosis is a problem when the number or protozoa in the chickens digestive system get out of control. If that bug is present in small numbers the chicken does not get sick and it will develop immunity to it in two to three weeks of exposure. Feed medicated with Amprolium reduces the reproduction rate of that bug but does not wipe it out so the chicken can develop immunity if it is exposed to that bug. If the chicken is not exposed to that bug, Medicated feed does not give immunity. One common problem is that people feed medicated feed while the chicks are in the brooder but the chicks are never exposed to the Coccidiosis bug that might be in their soil so they have not develop immunity. When they move them from the brooder to where they are in contact with the soil, they stop the medicated feed and the chicks can get sick. They did not use the medicated feed properly.

When chicks are vaccinated they use a weakened version of that bug. If you use medicated feed the first twp to three weeks after vaccination it can wipe out that weakened bug before they develop immunity. That's why they recommend you to not use medicated feed after vaccination for Coccidiosis, but by three weeks either they have developed immunity or they haven't. If you really want to you can use medicated feed after three weeks.

One more detail. There are several different strains of protozoa that can cause Coccidiosis. Immunity to one does not give them immunity to all. The vaccine protects them against most common strains but not against the rarer ones unless they have changed the vaccine lately. So whether you used medicated feed properly or not or whether they were vaccinated or not learn the signs of Coccidiosis and watch your chickens. If they have been vaccinated or if you used medicated feed properly it is really rare but possible they can come down with Coccidiosis from some strain they have recently been exposed to.

You have all kinds of options. If those chicks ere vaccinated more than three weeks ago, you can use medicated feed until they start to lay. The USDA says there is no withdrawal period for eggs if you are using feed medicated with Amprolium so you can use it even after they start to lay so finish off that bag of feed. Just provide oyster shell on the side so the ones laying can get the calcium they need for egg shells.

You can switch to another feed now if you wish. I would not use Layer until they are laying because of the excess calcium, but many of us never use Layer anyway. We may use Starter, Grower, All-Flock, Flock Raiser, or something else with a calcium supplement (usually oyster shell) on the side.

There is not one way to do this, there are many options. Hopefully this will help you determine which is right for you.

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