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How to Maintain a Closed Flock

How to Maintain a Closed Flock

How to maintain a closed flock

Maintaining a closed flock is a good way to keep your birds healthy and free of disease. Healthy, disease-free birds are more productive. Plus a disease outbreak can devastate your flock; some serious diseases may even require that you euthanise your birds and stop keeping chickens!

But there are different ways to keep a closed flock, and it isn't for everyone. Find out what "closed flock" means and whether it is right for your chicken coop.

What is a closed flock of chickens?

Closed flock can be a confusing term because it means different things to different chicken keepers. Generally speaking, a closed flock most often refers to either breeding practices or biosecurity.


In terms of breeding, a closed flock is where you breed chickens from within your own flock. This can result in the improvement of genetic characteristics, or even the development of a new breed! But if you do not follow good breeding practices, too little genetic diversity can lead to a range of problems.


For backyard chicken keepers, a closed flock is more likely to be related to biosecurity. New birds care common carriers of chicken disease, so by keeping a closed flock where you do not introduce any new birds, you greatly reduce the disease risk for your chickens.

How to maintain a closed flock

While maintaining a closed flock is about not introducing any new birds to your chicken coop, the term can refer to a few different approaches to chicken keeping.

A strictly closed flock

In a strictly closed flock, no new birds are introduced except those that have been bred from within the flock.

Obviously, this type of closed flock requires a good knowledge of breeding and a strict breeding schedule, because in-breeding will become a risk after the first generation. That said, in-breeding isn't as problematic in chickens as in some other species, so a closed flock can be maintained almost indefinitely without the introduction of new birds, if you start out with enough genetic diversity and manage breeding carefully.

A good number of unrelated birds are recommended for starting this type of flock. You will also need to be able to identify all birds and segregate groups for breeding.

A strategically closed flock

Many backyard chicken keepers who say they keep a closed flock do so strategically rather than strictly. While they do not introduce any adult birds to the flock, they purchase either fertilised eggs or day-old chicks.

The older a bird is, the more likely it is to have diseases. Some common diseases like Marek's disease, fowl cholera and mycoplasmosis can be carried by otherwise healthy birds, yet they can devastate your flock. Older birds will also carry coccidia, which can cause coccidiosis in flocks that are unaccustomed to that specific strain.

Though some unwelcome diseases such as mycoplasmosis, colibacillosis and Marek's disease are transmitted through the egg, the disease risk from fertilised eggs and day-old chicks is much lower than that of older birds. In particular, chicks and eggs from a certified hatchery or breeder, are unlikely to carry diseases that could infect your chickens. Chicks are often available vaccinated and by raising them in a brooder, it is possible to ascertain that the chicks are healthy before you introduce them to your flock.

This approach to maintaining a closed flock allows chicken keepers to manage the issue of in-breeding by introducing new genetics regularly or skip breeding altogether and maintain numbers by buying chicks or eggs.

All in, All out

An ‘All in, All out’ system is yet another approach to maintaining a closed flock, and is used by almost all commercial chicken farms. In this system, chickens are introduced to the coop in a single group, with a break or ‘spell’ between groups.

All in, All out works well on commercial farms, where birds are processed for meat or culled after a certain time period. In between groups of birds, the facilities are extensively cleaned and disinfected, and often spelled for weeks or even months. This prevents any possible spread of disease between groups.

While All in, All out can work for backyard chicken keepers, it works best where you are willing and able to cull, sell or give away your birds after a certain time period. If you wait for each group of birds to die of natural causes, not only will you have many years of poor egg production, you will eventually end up with a single chicken, and keeping a chicken alone is cruel!

If you are working in groups, you also need to think about where you get your replacement birds from, whether you will raise them yourself and how long you will spell your coop for. All of this will influence how long you go without eggs, or chickens!

Culling layers after 2-3 years is often the most economical option, particularly if you keep commercial breeds. But All in, All out limits your ability to raise your own replacement birds meaning you most likely have to buy in each new group of birds. Besides, most backyard chicken keepers are happy to let their birds live out their lives in peace and maintain egg production by adding new birds to the flock, so All in, All out is less common outside of commercial farms.

Should you keep a closed flock?

Keeping a closed flock isn’t for everybody. But different types of closed flocks work for many chicken keepers.

What are the benefits of keeping a closed flock?

The main benefit of keeping a closed chicken flock is the reduced risk of disease.

While other vectors such as wild birds and contaminated equipment could still pass disease on to your chickens, most common chicken diseases are much more likely to be introduced to your flock by new, adult chickens.

What are the problems with closed flock chicken keeping?

No matter what you mean when you talk about a closed flock, the greatest challenge will be maintaining bird numbers while avoiding genetic problems caused by in-breeding.

Deciding if a closed flock is right for you

With strictly and strategically closed flocks, you need to be committed to maintaining a breeding program or, at the least, buying and raising chicks. But for many chicken keepers, raising chicks is a joy! Plus, having a disease-free flock makes chicken keeping stress-free, not to mention cheaper!

With All in, All out flocks, you must stomach the cost of buying replacement birds periodically and resign yourself to having periods where you have no birds or no eggs. Plus, few chicken keepers want to dispose of their flocks periodically!

If you want to breed from your closed flock, a good knowledge of line breeding and other closed flock breeding techniques is required. This will both help to improve your birds and prevent genetic inbreeding. There are some great resources on breeding management available herehere and here. While you do need a breeding plan, closed flock breeding is easier than you think and in-breeding isn't such an issue with chickens.

When keeping a closed flock is non-negotiable

If your chickens have a chicken disease that they will carry for life, such as Marek's disease, you will have no choice but to maintain a closed flock. 

Of course, some chicken keepers choose to euthanise their chickens, spell their coop and start again with disease-free birds when their flock falls ill. Sometimes this is the kinder choice, or a necessary one. But with many common poultry diseases, the majority of your flock will recover and remain productive, even if they continue to carry the disease. If you wish to keep your birds, you must maintain a closed flock.

If you know, or even suspect, that your chickens are carrying some sort of disease, you should never, ever sell or give away your birds, as you will spread the disease to other chicken keepers and properties.

When your chickens carry a disease, you can’t introduce new birds to your flock either, unless it is possible to vaccinate them against whatever disease your chickens are carrying. For certain diseases, even chicks hatched from your own hens will need to be vaccinated!

If your chickens have a disease, maintaining a closed flock becomes non-negotiable. 

Depending on how long the disease lasts in the environment, taking an All in, All out approach might work. You can wait until your flock has died (or euthanise), spell the coop and introduce new, disease-free birds to start again. But some diseases, such as avian tuberculosis persist for so long in the environment that you won't be able to keep chickens in that coop for many years.

For more ways to keep your flock disease-free, check out these blog articles:

Happy chicken keeping!

Rachael at Dine a Chook Australia