How To: Maintain a Closed Flock 

Keeping a closed flock is one of the best ways to keep your chickens healthy and free of disease. Healthy, disease-free hens 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 what is a closed flock? And how do you keep one?

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 refers to either breeding practices or biosecurity.

Breeding

In terms of breeding, a closed flock is where you breed chickens from within your own flock. Usually you do this to develop a new chicken breed or improve an existing breed. This requires a good knowledge of breeding practices, as too little genetic diversity can lead to a range of problems.

Biosecurity

For backyard chicken keepers, a closed flock is more likely to be related to biosecurity. New birds are 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 keep a closed flock of chickens

While maintaining a closed flock is about not introducing any new birds to your chicken coop, there are a few different approaches to this type of 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 aren't being entirely accurate. What closed flock often means is that you do not introduce any adult birds to your flock, but you do purchase either fertilised eggs or day-old chicks for breeding.

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, but can wipe out a vulnerable 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 and colibacillosis 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, and leave as a group.

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 cull, sell or give away your birds regularly. It works for meat chickens and is a more economical option than keeping older hens that don't lay as well. But most backyard chicken keepers are happy to let their laying hens live out their lives in peace and supplement egg production by adding younger birds. Besides, if you wait for each group of birds to die of natural causes, you have many years of poor egg production and will eventually end up with a single chicken.

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!

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?

The greatest problem in a closed chicken flock is maintaining numbers whilst avoiding in-breeding. But if you have a strategically closed flock and allow in eggs or day-old chicks, this can reduce disease risk without the trouble of avoiding 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 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 here, here 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.

The best approach is to keep your flock disease free in the first place. Here are some tips:

• Easy biosecurity measures for the backyard chicken coop
• How to quarantine new birds and why you should bother

Happy chicken keeping!

Rachael at Dine a Chook