Inbreeding in chickens.

Well bred black breasted game chickens

Chickens will quite happily breed with any member of their own family, including brothers and sisters and parents and offspring.

What is inbreeding?

Inbreeding is the process of mating genetically similar organisms. Successful inbreeding is simply called line-breeding.

Of course, every breed of chickens, cow or dog we have today was produced by line-breeding, which is the art of mating closely related animals together to fix in their genetic make-up the qualities or conformation the breeder is looking for.

Some degree of inbreeding is involved when any pair of mated chickens have a common ancestor.

Below: I used inbreeding to fix this leg colour in my Barnevelders.

The close the ancestor to the mating pair the greater the degree of inbreeding.

Inbreeding does not create and by itself does not put anything in. It does not create either good points or bad ones. It only makes the best or worst of what is there. Hence the need to have all the good points at your disposal, with the object eventually of condensing them all in the best birds you breed.

Are chickens inbred?

All domesticated chicken breeds are inbred to some extent. The original wild chicken was the jungle fowl and any modern bird that differs in appearance from that has been inbred at some point to accentuate some features and remove others.

In humans, it's associated with consanguinity and incest, in which close relatives have sexual relationships and children. Inbreeding violates modern social norms, but is fairly common in animals and plants.


We now come to the very important question of in-breeding. " Be sure that the cockerel is not in any way related to the hens that you send me. " Such has been the sum and substance of hundreds of requests I have received over the years. Even in the present day an enormous amount of prejudice is shown by breeders, not only of poultry, but any other kind of live stock, when the subject of in-breeding is touched upon.

Before, therefore, going into the pros and cons of in-breeding, we would like to give one or two examples of the results of in-breeding that have — amongst many others — come under our own personal observation.

The effect of in-breeding is not only to establish a, high degree of pre-potency, but also to enlarge in the offspring certain peculiarities of form of latent tendencies possessed by the parent stock.

Does inbreeding affect chickens?

Yes. There are numerous reports and studies of how four or more generations of inbreeding effect the fertility, hatch-ability and viability of stock.

Inbreeding is the best way I know of exposing the genetic weaknesses in your chickens.

Can you breed brother and sister chickens?

Yes you can breed sibling chickens. Breeding brothers and sister chickens is commonly used to fix a certain characteristic in the birds.

I used it several years ago to ensure the bright yellow colours of the legs on my silver laced Barnevelders

This includes the breeding of chickens from the same hatch. Deciding to use inbreeding is not a decision to be taken lightly and require s some planning and your choice of birds should be good and you should not choose mate brother and sister chickens from the same hatchery fro example.

Chickens are a little more tolerant of inbreeding than many species. You can safely mate brother and sister chickens for at least a few generations.

The big problem with breeding together brother and sister chickens is that you merely reassemble the genes of the parent so unless this is your specific intended result, it is probably best avoided.

Breeding a brother and sister together will never produce a chickens that is of better quality than the parent. On the other hand, a young bird bred from father and daughter, for instance, can have a double dose of a particular desirable quality carried by the father

If you do too much inbreeding, the first issue you will run into will be a loss of fertility, which will result in a low or non-existent hatch rate.

Why is inbreeding a bad idea?

As, for instance, supposing we take two birds possessed of very large white lobes — say, brother and sister — and mate these two together, we shall probably produce a number of chickens that will be possessed of considerably larger lobes than either of the parent stock ; and if we continue in like manner to in-breed, not only the lobe but the whole face would eventually become white.

But exactly similar results would happen if the parent stock had some tendency Ito disease. The first time of in-breeding would produce progeny more liable to this disease, and perhaps in the next generation the disease would develop and destroy a large number. But such consequences are not obtained simply from the fact of in-breeding, but from in-breeding from unsuitable stock.

When to In-Breed.

When it comes to a certain characteristics, as in a show bird, where the comb has to be possessed of certain characteristics, where the shape of the head is fixed, the colour of eye, length of body, carriage, colour of plumage, legs, beak, and markings all defined in a recognised standard, then we say it is an impossibility to breed a fair proportion of such birds in a yard where inbreeding is not resorted to.

I know from experience what hard work it is to breed good birds and animals with a fixed type unless in-breeding is resorted to although it is not a system for every circumstance.

If you possess a second-rate birds, it would be futile to mate up your hens with one of the cockerels produced by them and it would be preferable to purchase a real good foreign blooded bird and put with them. So also would it be folly to in-breed from any specimens not in robust health.

The only cases in which I recommend in-breeding are these :

  1. Firstly, for the purpose of fixing some chance good point.
  2. Secondly, for the improvement of good birds.
  3. Thirdly, to maintain the high state of perfection that certain fowls may have been brought to. 

Do not use inbreeding if:

  1. If the stock is gaining or losing size.
  2. They do not appear to be healthy.
  3. They are developing some fault - consult a gene library a look up the gene in question.
  4. Fertility or hatchability are effected.

The effects of in-breeding is to increase certain characteristics possessed by the parent stock; to enlarge the pre-potency of the birds, and also to develop latent tendencies to disease should the stock birds be predisposed to such. But so long as no ill-effects are noticeable we would object to the introduction of fresh blood in a tip-top strain of exhibition fowls, so long as we could breed our chickens with not more than seven-eighths of the same blood in.

Above all things, always breed from the best birds, and although a bird with only one particularly good point may take your fancy, avoid it for breeding purposes — a fairly good all-round bird will produce better results than one that is perfect in one point, and faulty in all others." The latter portion of this quotation, viz., that a good all-round bird will produce better results than one only perfect in one point, is correct. But to advise the breeder never to breed from a bird that is perfect in one point, simply because ic is faulty in all others, is cutting nine-tenths of the ground from under the feet of the one who desires to improve any given breed.

Lastly, where we recommend in-breeding is in order to maintain the high state of perfection to which the stock has attained. Many a yard has taken years to regain the position that it lost, solely because its owner was tempted by the good looks of a certain cockerel to introduce entire foreign Hood. At the present day the evil results likely to accrue by the introduction of a male from another yard are not nearly so great as they were formerly.

Thus inbreeding may be said to be a double edged sword, and it is essential to use one edge only.

What is the difference between line-breeding and inbreeding?

The expression 'line-breeding' also implies the pairing together of related individuals, and it is a form of inbreeding. Actually the distinction between inbreeding and line breeding cannot be sharply defined.

It is often loosely stated that line-breeding is the use of more distantly related animals (including, of course, birds, which are feathered animals) and inbreeding the mating together of those of much closer kinship, for example, mother to son, father to daughter, or brother to sister. My view is that one can get as close as this when line-breeding, and employ more distant relatives when inbreeding.

Generally speaking, I consider that one is line breeding when a line is being established on a foundation sire or dam-the practice usually followed by breeders of the larger animals-and not line-breeding but certainly inbreeding when the fancier is mating the best related specimens in his stud in order to fix all the good points and eliminate any weaknesses, without actually using any particular animal as the prototype.

Can you line breed chickens?

Line-breeding is a form of inbreeding where a child F1, F" or cousin chicken is mated back to its parent. This is done with many types of animals to ‘lock in’ desirable traits. You do need to be careful though, you may also ‘lock in’ some undesirable traits as well.

Here is a whole article on line breeding and how it works.

What is a strain?

A strain of chickens is a flock with a single line of descent.

The word 'strain' is often loosely used by livestock breeders and authors.

Meany people claim to have a strain of their own when actually they have no such thing. They buy animals here and there; they may inbreed a little and that not very skilfully; they outcross frequently; they produce specimens of varying type, some good, some bad. They have no right to state that they have a strain at all.

Without inbreeding a strain cannot be founded. He who desires to establish one has to rely in the main on home-bred animals, whereas he who makes no attempt to build up a family line must, as I have already indicated, place his faith on specimens which he buys and which, of course, he has to do when he makes his first purchases, but which of necessity disappears after a few years.

It is also worth bearing in mind that if you acquire birds from another "strain", it ceases to be that until you create your own. Strains are not bought, they are produced over years with effort and skill.

How to Form a Strain:

Creating a strain requires years of selective breeding from pairs of birds with specific characteristics.

Eugene Davenport in The Principles of Breeding (Davenport—The Principles of Breeding: Thremmatology (Ginn & Co))wrote:

"By "line-breeding" is meant the restriction of selection and mating to the individuals of a single line of descent. The purpose of this system of breeding is real breed improvement, to get the best that can be gotten out of the race, and better than ever before if possible. Experience has shown that if the purpose be breed improvement carried to its limits, it is not enough to confine selection to the limits of the breed. All breeds are exceedingly variable, and real results aiming at anything more than mere multiplication can follow only closely-drawn lines within the breed—breeding in line, or line-breeding."

And also:

"Line-breeding excludes everything outside the approved and chosen line of breeding. It not only combines animals very similar in their characters, but it narrows the pedigree to few and closely related lines of descent. This "purifies" the pedigree rapidly and gives the ancestry the largest possible opportunity. The system is eminently conservative. It discourages variability, and rapidly reduces it to a minimum. Moreover, whatever variations do occur will be in line with the prominent characters of the chosen branch of the breed."

Selection and elimination: The golden rule of inbreeding can be expressed in two words selection and elimination. Selection of the right mates as indicated by appearance and pedigree; ruthless elimination of any bird that is for any reason undesirable. The outcome of an inbreeding plan will give satisfaction or dissatisfaction according to the quality of the birds used in the breeding team each season—that is the quality of the related birds mated and their suit- ability to each other as mates, judged by both appearance and pedigree.

Close inbreeding must never be undertaken unless the fancier is convinced that the birds he uses are themselves possessed of the qualities which he desires to fix in his flock. 

To inbreed with poor birds would lead to the production of a strain of inferior quality, even though the birds bred would all be of one general type because of the effect of inbreeding. The successful in-breeder produces birds all with a family likeness, but they are of high quality, not mediocre.

Degree of relationship: When inbreeding I am not so concerned as to whether the relationship between the members of a mated pair is near or far as I am with the suitability of the two birds as mates. I don’t deliberately breed from very closely related birds because they are closely related; I prefer a rather more distant relationship if 1 can achieve my object. As a matter of fact, after a few seasons of skilful inbreeding one can be so sure of the high quality of the pedigree of each member of the breeding team—so certain that there are no undesirable latent properties—that a point is reached when pedigree can almost (not entirely) be ignored and mates selected by analysis of visible qualities only.

I am often asked if there are any particular relation ships which I favour, providing the two birds to be paired satisfy as regards their appearance. I can only answer this in a general way, as will be understood in view of what I have said in the last paragraph. I like uncle and niece, aunt and nephew, cousins, father and daughter, mother and son, grandfather and granddaughter, grandmother and grandson. I particularly favour half-brother and sister when the parent of both is a bird of outstanding merit.

I never mate brother and sister unless the two birds are of exceptionally high quality or I am doing it for a specific purpose. The offspring of brother and sister can only have in their genetic composition the characteristics of the two parents reassembled, and you are not likely from such a mating to produce a bird better than either of its parents.

Build up the fabric bit by bit. My experience is that you cannot reach a certain point as quickly if you attempt to do it all at once as you can if you make slow and sure progress by doing a bit at a time.

Foundation birds: Sometimes we discover that we are the owner of a bird which is exceptional. For the sake of illustration we will assume it is a cock. It may not be one of our big winners. It may be inferior in exhibition to its own brother, and yet it breeds youngsters of surpassing merit. This can be a foundation sire or it can be a dam. We can establish a line within his own inbred family by breeding daughters and grand-daughters back to the father, or the father’s best sons, grandsons and so on—in fact, always going back to direct line descendants of the foundation bird on which the line is being established.

The quality line: The breeder needs to set a quality line, and any bird or animal which falls below that line must not be bred from. Every year onwards that quality line must be raised higher. Never should a bird be kept merely to make up a pair. There must be a definite and well understood reason for every pairing. This is the occasion when the rule of ruthless elimination should operate to the full. The selection of mates should be made ‘on paper’ well before the date of the actual commencement of breeding. The preliminary list of pairs will no doubt be changed as time passes, so that when the actual mating time arrives the breeding team is as near perfect as it can be.

Of course, just as a good property can be improved, so can a fault be intensified if it is shown by both mates of a pair, or if their respective pedigrees disclose it is a family fault carried by ancestors on both sides of the mating.

Health and vigour: When inbreeding not only has one to take into consideration the virtues of the pedigree (and also the weaknesses, if any) and the appearance of the bird or animal to be mated, but also its health and vigour. An animal which has ever had an illness or was a ‘bad doer’ as a youngster, or has ever had a set-back to its development, should never be used for breeding purposes. The reason for this is that inbreeding can fix weakness of constitution if proper precautions are not taken.

If there is a tendency to infertility in any of the animals used, then inbreeding can accentuate it, although inbreeding itself will not cause it.

Effect of age: A common fallacy is that stock is more capable of breeding youngsters of high merit in their early breeding years than they are when they can be described as aged. And another mistaken idea is that the best young ones are bred at certain times of the year.

Age should never be a deciding factor in the selection of chickens for breeding. Any bird that is old enough to have properly developed it's adult character and form should be considered.

I try to pair together either two comparatively young individuals, an aged male to a young female, or a young male to an older female.

What is a Taint?

There is a natural desire on the part of some owners, especially novices, to take a short cut to success. Sometimes this is temporarily rewarded by the breeding of a few winners earlier than would occur in the ordinary way. But this short-circuiting can be dangerous and in the long term the cause of dismal failure.

Frequently this urge to achieve with rapidity that which might normally occupy a number of years in the case of exhibition livestock is created by the judges. They develop what is known as a one-point craze. Exhibits excelling in a certain property are given high honours, even though they fail rather badly in one or more other properties. Being desirous of showing the type of bird or animal which, with an appalling lack of sense of proportion, the judges prefer to the better balanced good all-round exhibits, they set about to breed them, and take extreme risk in so doing.

A breeder who knowingly introduces a taint must never inbreed or he will fix that taint even more quickly and more firmly.

Pre-potency: Pre-potency is the power possessed by an individual fowl of imprinting his or her likeness upon the offspring to the exclusion of the likeness of the other parent. A strain of fowls that have been carefully bred for a number of years will be pre-potent to a far greater degree than chance-bred fowls of the same breed.


The practical application of the principles on inbreeding is not difficult if the breeder exercises common sense and feels that he knows exactly what he is doing as regards the choice of the animals from which he is to breed, and the way in which he mates them.

When he starts to establish a flock, the better the stock he uses, the more will be the good properties they possess, and the fewer the faults; therefore, the sooner is he likely to reach his objective. Better by far have few in numbers of high quality than many inferior specimens.

An elementary rule in mate selection, which applies also when unrelated individuals are paired, is never to put together a male and a female which both have the same fault, even a minor one.

Possibly the most important part of inbreeding is record keeping and numbering the hens and cockerels properly.