Table of Contents
- How to breed chickens.
- Natural variability.
- Why then do I prefer the hen as a breeding force?
- The practice of breeding.
- What is the coefficient of in-breeding?
- What is the difference between in-breeding and line-breeding?
- Out-breeding or out-crossing.
- Blending the out-cross.
- What is a mutation?
- The bulk or numbers method of breeding.
- Some examples of poor breeding practise.
- Genes that can kill in poultry.
- List of the common lethal genes in chickens and ducks:
- What is a strain?
- A word about Hybrids:
- Meet the monk and his peas - Gregor Mendel
- Dangers of incorrect breeding:
- Selection and elimination.
- Degree of relationship
- How long does it take to breed good birds?
- Foundation birds
- In-breeding in practice
- Selection criteria and characteristics:
- Reducing the risk:
- What is a taint?
- Successful examples of in- or line- bred stock:
- Answering the critical:
How to breed chickens.
Anyone can breed chickens, they do most, if not all the hard work for you. There is little to do other than to let the chickens get on with what they do best and making sure they are well fed and in good condition.
The choice of which bird to breed with is an entirely different matter. Breeding chickens is easy. breeding the properly requires skill, thought and planning.
When I was quite a bit younger and had only recently started breeding chickens I was admiring some of my young birds that were well grown but yet to be fully mature when I was interrupted by a local farmer of considerable age.
We chatted a while about the birds and found myself completely stunned with his line “You should put the brother over the sister to fix the colour”
Being horrified as I was at the time, I thought that inbreeding was something to avoid at all costs. It is illegal in humans after all.
At the time I had plenty to learn but I now know there is sometimes much value in a related match and this is a topic that is like Kennedy said about peace, much misunderstood.
There are many and divided opinions about which is the more important member of a pair, the cockerel or the hen. My view is that, as a rule, they are almost of equal importance, but if I have a leaning it is in the direction of the hen, though according to genetic rule, one sex has no more power over the quality of the offspring than has the other sex.
One of the more obvious fact about living beings is the variability they display. If you look at chickens or ducks the world over even the most untrained can see the difference, be it size or productivity. It was in this variability that the need was seen for improvement.
So followed the breeding of types by selection. Shire horses, Wyandottes and Jersey cattle to name a few have all been created by selecting animals and breeding them to externalise certain points of note.
Weather or not you agree with the selection and process it is merely and extension of natural mechanisms to bring characteristic out in an animal which we find useful. Like the winter laying ability of the Barnevelder, the fine meat of the Bresse Gauloise or in the past the fighting prowess of Malaysian Saipan.
It should be remembered that genetically a character can show as easily because of the absence of a gene as it's presence and the idea behind selective breeding is to limit the variability that naturally occurs.
Why then do I prefer the hen as a breeding force?
Hens and cockerels are supposed to contribute 50% each but sometimes characteristics belong to a particular sex.
I have learned through many hard lessons that you cannot correct the lacing on the feathers of a Barnevelder hen by the selection of the male, the latter being single laced. Whether the same is true for Wyandottes and other laced types I do not know.
It can be more difficult to judge the feather patterns of the male in some birds.
The egg colour follows the Dam or female line more in chickens.
The practice of breeding.
On a purely physical level breeding starts with making sure the cockerels are doing their part and that you have fertile birds that are not overstretched, so no more than 6 or 7 hens to a male or less in the case of bantams.
Select birds for mating that conform to their respective breed standard if you a planning to sell the eggs for hatching or to raise on and for the type of breeding you are doing. So select Pairs, trio’s or groups as appropriate. It may sound obvious but sometime people forget the simple - in poultry one cockerel runs with any number of hens in a breeding pen so make sure he is a good one.
Breeding is a real art, one which demands a high degree of courage. Altogether too many people would prefer to have an animal which appears to be a splendid individual on the surface, but which is likely to pass on undesirable traits.
- Check the legality where you live. Not every one can keep cockerels.
- Have the incubator and brooder ready before you start.
- Probability dictates breeding results in 50% males that will need dealing with.
- Suitability and type. Compliance to the breeds standards.
- Choose your breeding flock to compliment your objectives, Pairs, trios of group.
- Healthy Birds. Examine your breeders for good health. I was once told not to breed from a bird that had been ill in the last 12 months.
- Egg selection for hatching is very important and overlooked by many. Size, shape, colour and shell porosity.
- Egg Storage and care. Eggs stored before incubation need care before use.
- Keep accurate records, leg rings, ID's and learn how to trap nest if necessary.
The best eggs to collect for hatching are those laid in the birds second spring. Second because the eggs are bigger in the second year which makes for stronger, larger chicks and fertility seems to be better in spring.
Also a point many people overlook is that some rare breed take a considerable time to mature a fill out properly and early selection of breeding stock may be wrong.
The rooster has a small phallus that becomes engorged with lymph to form a copulatory organ. It is more of a swollen lump in chickens rather than a protuberance. The copulatory organ is rudimentary and at the time of mating there is practically no penetration. The hen everts her vagina during copulation, which helps to transfer the semen into the oviduct. Ducks, geese and some other birds have more well-defined copulatory organs.
An understanding of the natural mating behaviour in chickens can help the breeder manager. Mating behaviour follows a diurnal pattern and is best seen early in the morning or in the evening before roosting.
The completed mating in chickens is the culmination of a sequence of behaviours. The rooster will start the mating by exhibiting courtship behaviour: dropping one wing and dancing in a circle (the lowered wing will be on the inside of the circle dance).
The hen will crouch and brace (dip her head and body) to indicate receptiveness to the male. The rooster will then mount the hen and grab her comb, neck feathers, or the skin on the back of her head or neck to help hold onto the hen's back.
The next behaviour is the tread. The rooster steps on to the hen's back and completes the behavioural sequence. The completed mating occurs when the rooster dips his tail to the side of the hen's tail and spreads his tail feathers so that their cloacae come into contact. At this point the rooster's ejaculate is released directly into the hen's vagina via her cloaca.
A rooster may mate from 10 to 30 or more times per day, depending on the availability of hens and competition from other roosters. The rooster usually ejaculates between 100 million and five billion sperm at a time with greater concentrations produced at the beginning than at the end of the day, when depletion occurs after many matings.
The number of sperm per ejaculate is seldom less than 100 million which is the minimum required to maintain high fertility. With natural mating, better fertility will result when mating occurs after the hen has laid a hard shell egg.
If the hens are mated daily there is unlikely to be a noticeable difference in fertility regardless of when the mating occurs.
I always feel a bit sorry for the hens as all they get is squashed and pulled ruffled feathers. Chicken foreplay seems to involve chasing the hens around and grabbing their ruff feathers.
On a practical level I can recommend removing the tip of the spur or blunting with a nail file as they can damage the hens. Make sure the cockerel has enough hens to keep him amused or he may literally shag the feathers off the hens and this can lead to sunburn and all sorts of troubles.
In-breeding -The definition of the term 'inbreeding' is the mating of relations, blood relations. Except that the word as livestock breeders use it goes a distance beyond that.
If you are breeding pure or heritage chickens then there will always be an element of inbreeding involved.
In my experience most inbreeding starts with the purchase of a trio at auction or the hatching of eggs purchased from somewhere like eBay. I have only rarely seem quality stock at either of these places and your chances of failure using this method will be 9 in 10. I have tried both many times and am always disappointed.
Remember these simple breeding guidelines:
- There is no physiological law against reasonably close inbreeding, the results of which can be both good and bad and follow genetic laws.
- Inbreeding contributes nothing new in a line. It results in a line becoming more homologous or ‘pure’ for certain qualities which may or may not be desirable to the breeder, depending on both chance arrangements of the genes and the genetic basis of the original stock.
- Out-breeding tends to hide defects, but it does not eliminate them. Inbreeding discloses them as the line becomes more homozygous, but is not the cause of the defects.
- Selection in an inbred line of the most desirable individuals enables the breeder to remove defects from the breeding pool.
What is the coefficient of in-breeding?
Ever since man started breeding types and selecting for genes, animal breeders knew that breeding related animals produced more consistent, predictable traits in the offspring, but they also found that for some there is loss in vitality and vigour.
Fertility tended lower, offspring were smaller, early mortality was higher, lifespan tended to be shorter. This was not always the case.
These things that reduced their profit and the quality of their animals and the higher the level of inbreeding the greater the detrimental effects.
Both the benefits and the risks of inbreeding are a consequence of homozygosity. This is essentially when both copies of the gene inherited from both parents are the same.
So a statistic was devised that estimated the level of inbreeding that would result from a particular cross so breeders had a quantitative way of evaluating both the risks and benefits.
Is there a good value for COI and what is too high?
The original purpose of the coefficient of inbreeding was to give breeders a number that shows both the benefits gained from inbreeding as well as the magnitude of the deleterious effects they could expect.
The trick for the breeder then is to weight the benefits and risks of a particular breeding and judge what is an acceptable balance. A low COI will have low risk, but it will also only have a modest benefit. A high COI would produce more consistency and pre-potency in the offspring.
The trade off is with poor selection and breeding of bad qualities there will also be a significant loss of vigour and health.
For comparison, mating of first cousins produces a COI of 6.25% and in many societies is incest and forbidden.
Mating of half-siblings produces a COI of 12.5%.
Mating of full siblings produces a COI of 25%.
Line-breeding implies the pairing or grouping together of related individuals and is a form of inbreeding.
There is a distinction between in-breeding and line-breeding. The is not a clear line in the sand that divides the two methods.
I would put forth that the difference between the two is the number of generations involved in the program.
Be aware that the all rare breeds today have been created by selective breeding which has always at some point involved in- or line-breeding.
It is often stated that line-breeding is the use of more distantly related 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 you can get as close as this when line-breeding, and employ more distant relatives when inbreeding. Both in breeding and line breeding are to an extent inseparable as they are not mutually exclusive.
Line-breeding should follow in-breeding only after unwanted aspects of the birds have been bred out as the idea after all is to establish a line of birds.
I both in-breed and line-breed as well as mate completely unrelated individuals. I not only roll up the good properties in families, but I also make the fullest possible use of birds which prove to be foundation sires or dams.
I am not so concerned about 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 breed from related birds because the fact. I prefer a rather more distant relationship if 1 can achieve my objective.
What is the difference between in-breeding and line-breeding?
In-breeding is used when the poultry fancier is mating the best related specimens in his stud to fix all the good points and cut any weaknesses.
Line-breeding when a line is being established on a foundation sire or dam. The practice is to select the desirable male of female and breed the offspring back to the chosen individual to set the coveted characteristics.
Never rule a bird or match out of a breeding program because of it's relation to another!
Davenport probably said it best in his book. (Davenport—The Principles of Breeding: Thremmatology (Ginn & Co))
"Three forms of in-breeding are possible among animals, namely:
- Breeding the sire upon his daughter, giving rise to offspring three-fourths of whose blood lines are those of the sire. A practice which, if followed up, soon results in offspring with but one line of ancestry, thus practically eliminating the blood of the dam. This form of breeding is practiced when it is desired to secure all that is possible of the blood of the sire.
- Breeding the dam to her son or sons successively, thus increasing the blood lines of the female side. This form is practiced when it is the dam’s blood lines that are to be preserved and condensed. Both systems are necessarily limited to the lifetime of the individuals involved. Either system can of course be approximated by the use of grand-daughters or grandson, which would by common consent be called inbreeding. A relationship more remote would generally be regarded merely as line-breeding.
- Breeding together of brother and sister. A form of inbreeding which preserves the blood lines from both sire and dam in equal proportions. It is inferior to either of the others as a means of strengthening previously existing blood lines, but it is freely employed when the combination has proved exceptionally successful, virtually establishing a new type. It has all the dangers of the other two, and in a larger degree, because we have practically no acquaintance with the new combination, whereas in strengthening the proportion of one line of ancestry over another, whether it be that of the sire or that of the dam, we are dealing with previously existing blood lines known to be harmonious.
Nobody claims advantage of inbreeding per Se, but it is the act of line-breeding, and when superior individuals are at hand it is the most powerful method known of making the most of their excellence. It is the method by which the highest possible percentage of the blood of an exceptional individual or of a particularly fortunate "nick" can be preserved, fused into and ultimately made to characterise an entire line of descent of both sides."
Out-breeding or out-crossing.
The introduction into a pure line of a bird or birds of another breed, variety or strain. Achieved in one or more matings to secure from the breed out-crossed upon some particular trait.
Yellow legs into silver laced Barnevelder. In this example the yellow legs were introduced from a Bantam Barred Rock. the difference in the leg colour is clear to see from the previous generations.
Below: The offspring has better yellow legs than the parent.
The idea is to infuse into the pure line a dash of new blood for purposes of vigour or some desired characteristics.
The young of the out-cross are mated back into the pure line in successive generations until the percentage of blood of the out-cross is negligible.
An example of this is using a Silver laced Wyandotte in the creation of the Silver laced Barnevelder. A suitable Barnevelder hen is selected and bred to a Silver Wyandotte male. This is the out-cross. Selection then takes place with further matches until the desired result is produced. This is more complex than it may appear at first especially in some breeds.
Studied and responsible out-breeding is valuable, and is often combined with in- or line-breeding. This may be necessary to correct some fault which is becoming dominant in a strain; or to improve some weakness or lack of stamina which may result from too long continued inbreeding from original stock which was not fit to carry the responsibility.
You should take the same care with the bird you intend to breed into your flock. If you are unsure of the pedigree of the incoming birds, obtain a pair or more and breed them together (in-breed) to assess their potential before you even consider the out-cross.
Crossing out to another bird has other problems, A group that has been confined in a line-breeding program for a few generations becomes a kind of pure breed of its own. A breed within a breed, so to speak. Attempt to introduce blood from other lines is likely to be followed by all the pains and penalties of hybridisation.
Departure from line-breeding is a kind of crossing however small the degree.
Blood lines rapidly become intensified so that line-bred animals assume all the attributes of distinct strains, as they in truth are, and they will be likely to behave as such ever after.
After saying that line-bred animals tend to behave like pure strains, and that their progeny from union with other strains behave like hybrids, it is not meant that such unions should never be made. It may well be a necessity.
In truth some lines are so stubborn as never to blend with others afterword, behaving instead like strongly established races. Most of them will yield to well directed and persistent effort and in time made to assume the characters of another family but the process is attended with a struggle and more than a few failures.
It has been fashionable at times to decry line-breeding, but the fact remains that few generations of good breeding soon bring the flock and its carer to a point where line-breeding must be practiced or a worse alternative must be accepted.
Blending the out-cross.
This method of breeding is useful in introducing into a pure strain some desired characteristic which it does not have or in which it is weak. Provided the characteristic is recognisable in the bird selected.
Blending is gradually incorporating the offspring of the out-cross into your flock of chickens in a regular and planned way over two to three generations.
What is a mutation?
Mutations: A sudden departure from the parent type in one or more heritable characteristics, caused by a change in a gene or a chromosome.
This is something most of us back-yard breeders have little or no control over as they tend to happen spontaneously. Sometimes as a result or viral infection or radiation.
Note that it is a viable option for a desirable or undesirable trait to show up. You can then favour it and breed for, or cull away from.
The bulk or numbers method of breeding.
This is a wasteful method as it produces many birds that may in practice never be useful. Any excess hens may well have value as laying birds in home flocks but the males are very often wasted.
Chickens run in a flock and raised in large numbers every year. The top 1 to 2 % are then selected for breeding the next year. In practice this may involve many cockerels and hundreds of hens. More likely in the backyard flock it will be a single male and 8 to 10 hens.
There are some advantages to this method. It tends to be used in third world situations where the selection pressures are hard and the weak are quickly done away with. only productive and vigorous birds make the grade.
There are disadvantages to this type of breeding. If you have not first assessed the genetics of your birds you may be setting undesirable characteristics without realising it at first.
Even if you have hundreds or thousands of chickens this is still in-breeding and line-breeding combined in a hap hazard way.
You could end up inadvertently breeding stock with a low structural bone mass or that are susceptible to a particular disease.
Some examples of poor breeding practise.
I have no wish to pick on any individual or website but I have had to get my examples from somewhere.
My first is a bugbear of mine. Disparate or divergent hatches. It involves people who will not stick to the planned 21 days of incubation. If you allow chicks to survive and breed that hatch early or late you are introducing problems. Waiting and extra day or two to see what happens is asking for hatches that take 5 days or more to finish. Nature has an admittedly cruel way of selecting for the correct incubation period but it has served the species well in the past. In a similar vein chicks that hatch early as much of a problem and often have defects or malabsorbed yolks.
On a related note chicks that are too weak to hatch on their own will not make healthy breeding stock. I have had to give up several Facebook groups because I cannot sit idly by while people help chicks hatch or leave eggs a few days more.
Splayed legs should be culled immediately. Splaying of the legs may have genetic or environmental causes.
Persevering with birds that have poor fertility, if you carry on it will get worse.
Egg quality, size and colour. Egg colour passes down the female line as a rule although there are as many as seven genes in play. Avoid selecting porous or weak shelled eggs. see all about eggs and selection here.
The commercial egg and broiler industry has selected for behavioural traits for a great many years, resulting in hens that are fearless of humans and less likely to be cannibalistic or feather peck.
In my experience it is quite possible to select for hens that keep a clean nest.
Genes that can kill in poultry.
Sometimes genes associated with beautiful traits such as short legs on the Japanese bantam or Scots Dumpy and the crests on Crested ducks are mutations of normal genes. In the wild these birds would have died or eaten by predators.
Wild animals that have one quarter of their young never hatch will probably not thrive as a species, it is only human intervention that allows these types to survive.
We have selected over decades of breeding and birds with these desirable genes has lead to undesirable traits being passed into the future.
In this example Crested duck are C and non-crested are c.
If you breed two non-crested ducks (cc x cc) then all the offspring are cc and have no crest.
If you breed a crested (Cc) and non-crested (cc) duck 50% of the young will be crested (Cc) and 50% no crest.
If you breed two crested birds (Cc x Cc) 25% of the young will be no crest, (cc), 50% will be crested (Cc or cC) and a quarter will have two crested genes (CC) and as such will be crested but never hatch. This is a lethal gene if two copies are present.
The presence of lethal genes means your hatch rate is automatically reduced by 25% before you even start to breed.
It is worth looking in to whether your chosen breed is associated with lethal genes or has any well documented genetic problems.
List of the common lethal genes in chickens and ducks:
Dark Cornish carry a similar short-leg gene that causes death at the time of hatch. Signs of "Cornish lethal" include short beaks and wings, and bulging eyes.
New Hampshires carry a lethal that causes death in the twentieth and twenty-first day of hatch. Signs are crooked necks, short upper beaks, and shrivelled leg muscles.
The silver gray Dorking has a lethal that causes death in the ninth day of incubation. Embryos have short necks and beaks.
A Barnevelder lethal causes "Donald Duck syndrome", in which the upper beak curls upward, the lower beak curls downward, and death occurs in the last days of incubation. I have bred Barnevelders for many years and never seen this one.
Congenital tremor is a lethal gene found in some breeds including Ancona, Plymouth Rock, Rhode Island Red, white Leghorn, and white Wyandotte. Chicks hatch but can't control their neck muscles. When a chick tries to stand, its head falls over and the bird falls down. Unable to eat or drink, it dies soon after hatching.
Black Minorca - short legs with extra toes.
Rhode Island Red - short legs, wings, and beaks.
White Leghorn - short legs and parrot-like beaks.
White Wyandotte - early embryonic death.
Creeping genes in chickens giving rise to short legs. Found in birds such as in Scots Dumpy, Serama or Japanese bantams.
Common genetic factors that don't qualify as lethal genes, but that do reduce hatch-ability, are frizzledness and rumplessness and large crests in Polish.
Tufts in Araucanas.
What is a strain?
The word 'strain' is often used by livestock breeders and authors but more commonly by those who have acquired chickens by whatever means and claim them to be from a certain “strain”. Usually to help them sell their eggs on eBay!
When laying the foundations of a strain it is desirable to begin with a few pairs of birds of the best possible quality, those with few failings and obvious pleasing features. These need not be big winners purchased at high prices. They must be at least what a fancier would describe as good reliable breeding stock. Possessing among them all the desirable points of the breed and few bad ones.
I have never yet seen the perfect chicken but I have seen a few that came close. But the weaknesses should be in minor points only and major failings are not tolerated. The moral is to buy the best birds you can afford at the outset, and have few pairs of good ones rather than more pairs of inferior ones.
People claim to have a strain of their own when actually they have no such thing. If you buy birds from someone who has a strain it ceases to be theirs when you own it. They obviously cannot be responsible for your breeding choice.
If you buy animals or hatching eggs here and there and inbreed a little and out-cross frequently you will produce specimens of varying type, some good, some bad and that not skillful breeding.
Without inbreeding a strain cannot be founded and without effort, practise, and perseverance you have no right to state that you have a strain at all. If you place your faith on specimens you buy you will fail in the long term. Breeding a flock of birds for three years or so does not qualify as a strain.
Of course you have start somewhere and this is when first purchases are made. If you have the need to keep buying birds then mistakes are being made along the way.
The ultimate ideal of the fancier imbued with high ambition is to own a collection of home-bred animals or birds all of high quality and all so alike in general appearance that they are distinguishable as being of a certain ownership, this is a strain.
When he has achieved this, then, and then only, can a breeder claim to have a strain worthy of his name. Great success as an exhibitor cannot alone give him the authority to make this assertion, because he may have won most of his prizes with purchased animals or with some home-bred specimens unrelated and dissimilar in general characteristics.
Named strains - Comparatively few true strains exist. And as a rule they do not mix. Buying a sire and dam from different strains is as likely to fail miserably as it is to succeed.
A word about Hybrids:
I have no intention of using actual genes unless in examples, this is conceptual and I will write about in-breeding from the practical breeder's viewpoint. Not that of the geneticist.
In these days when the scientific approach to almost everything in life is receiving so much attention and publicity, there is a danger of people thinking that unless they become amateur scientists they have but little chance of achieving success.
PHENOTYPE AND GENOTYPES:
A phenotype represents the sum total of all apparent characteristics of an organism, regardless of what may be covered up beneath the surface. It includes not only what has developed out of the innate germinal resources and become evident, but also many superficial and transient visible modifications, brought about by the action of the environment and various external causes that play no enduring part in heredity.
The genotype, on the other hand, represents the total hereditary possibilities stored within the invisible genes. It is what the organism actually is, so far as its capacity for inheritance is concerned, regardless of what it may come to look like.
"Like breeds like" is a true enough saying, but give consideration to what the parents are like. It is necessary to examine the phenotypes to which the genotypes give rise in order to know what the genotypes are made up of.
Unfortunately for the investigator, phenotypes are not always what they seem to be. The popular phrase that “like produces like” is by no means always true, and it is the exceptions to this rule that give rise to some of the first puzzles that the student of heredity has to solve.
Arranging a mating that produces quality stock requires an extensive knowledge of the breed and this is where the study of a pedigree comes in.
Without a look into the birds past you may find hidden flaws showing at some later match. Atavism, or throwing back can assert itself unexpectedly, after several generations.
This shows the importance of a careful study of pedigrees on both sides, and a careful consideration of the prevailing family characteristics.
Meet the monk and his peas - Gregor Mendel
The father of modern genetics is Mendel who started by breeding peas in a monastery garden. In a pea-pod (nutshell) it was in this scientific environment that Mendel set out to study the 30-odd subspecies of the common garden pea. A vegetable noted for its many variations in colour, length, flower, leaves and for the way each variation appears defined.
Over the years he isolated each pea trait one at a time. Crossbred them and note what traits passed to the next generation and which did not. He established the principle of hereditary traits and the dominant and recessive characteristics of what we would come to know as genes.
You may think you need to understand Mendelian concepts to breed class winning specimens with certainty. This is not the case.
Many successful breeders know little about genetics. I have known scientific types who have never bred winning specimens.
Mendelism is a fascinating study for those with a scientific background and interest. It is not essential in so far as the breeding of better stock is concerned. It has shown us that the rose-comb is dominant for instance and that the ordinary straight comb is actually the absence of a gene.
Dangers of incorrect breeding:
Poor selection and bad breeding of any type can fix faults as by good breeding one can fix desirable features.
Thus inbreeding is as much a two-edged sword as an essential tool.
Inbreeding is the mating of related individuals – those individuals with common ancestors.
High levels of close inbreeding can impact the health of individuals. It may increase the chances of a specimen being at risk for both known and unknown inherited disorders. It could also have an impact on the breed as a whole, for example, a reduction in offspring size and fertility.
It is impossible to make precise predictions about the exact impact that poor choice with in-breeding has on an individual. We do know that as the degree of in-breeding increases, the risk of having a serious and harmful impact on the breed as a whole can increase.
The coefficient of inbreeding, how can you measure it?
The degree of inbreeding is measured using a Coefficient of Inbreeding or COI.
It is the probability that two copies of the same variant of a gene are inherited from an ancestor common to both the sire and dam. The lower the degree of inbreeding, the lower the inbreeding coefficient.
In some species the deleterious effects of inbreeding begin to become evident at a COI of about 5%. At a COI of 10%, there is significant loss of vitality in the offspring as well as an increase in the expression of deleterious recessive mutations.
The tendency for genetic problems to multiply with in-breeding can drive a population to extinction. Above a COI of 10% the level of in-breeding at which smaller litters, higher mortality, and expression of genetic defects have a negative effect on the size of the population. As the population gets smaller the rate of inbreeding goes up, resulting in a negative feedback loop that drives a population to extinction. This is an extinction vortex and it requires a minimum population number to avoid it. Or sound stock and good choice of studs.
It helps that birds are more immune to being inbred than humans for example.
To inbreed correctly demands experience and skill.
Incorrect in-breeding or line-breeding can be more damaging than out-crossing.
Any person can mate poultry so that the youngsters will be an improvement on the parents, and in due course establish a strain of his or her own.
The good in-breeder works always under a set breeding plan, without deviation. It should be a working document that can change from one year to the next as the flock develops.
The great purpose of inbreeding is to fix the good points and eliminate the bad.
To produce specimens of one good type and all bearing a family likeness.
It insures that every individual in a stud is related but not necessarily closely related to every other.
The words of Lewis Wright, made public in 1874 as expressed in a series of articles in the old Fanciers' Gazette, received more scorn than praise.
"Continue to out-cross and never mate related animals if they can avoid doing so. They may breed winners, but those winners are not similar in type."
As the years have passed the scorn has diminished and the praise increased, and yet there are still many who scoff at inbreeding and continue to make their matings in a haphazard way
If you do not have a breeding program that mates related individuals you will have to own a flock of vast size or buy new birds all the time.
Buying new birds all the time is at best a headache.
Objections in in-breeding are born of ignorance of the subject.
Selection and elimination.
There are few golden rules in poultry.These are three.
- Selection of the right mates as indicated by appearance and pedigree.
- Ruthless elimination of any bird that is for any reason undesirable.
- Avoid, as far as is possible, intensifying faults or constitutional weaknesses.
Decide what traits are essential and what faults are intolerable. Character and temperament must be included. Next Develop a scoring system and score selected good and bad faults with your breeding aim in mind. Then breed consistently with your chosen method to the best individuals produced and further improve your strain.
Understand that type and colouring of poultry is easy. The hard part is the unseen character and flaws.
It is necessary to breed your birds together for a year or two to see what undesirable character manifest themselves and you wish to breed out. Guessing is never a good idea.
People always think I mean killing when I use the word culling or elimination. There are plenty of customers for garden birds and those not selected for breeding will have long and happy lives producing eggs.
The outcome of an any breeding plan will give satisfaction or dissatisfaction according to the quality of the birds used.
Birds need to be given time to mature fully before becoming part of the breeding team.
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. Birds must be assessed on their merits and appearance and on your knowledge of the appearance of their ancestors.
One can eliminate these by in-breeding linked with strict selection.
In the early stages of the carrying out of a breeding plan there will appear youngsters which display faults. They are inferior to their parents. These shortcomings in the family are not always seen in the parents, but carried by them latently.
It is these appearances of weakened youngsters in the early stages of in-breeding that so often brings the practice criticism. In reality it ought to receive praise for surfacing the weaknesses in the flock.
It is the inability or unwillingness to select and cull that leads to the problems in future generations.
If the parent birds had not relatives the failings might have remained latent. Now come to light and can selected against.
The youngsters from which the fancier will breed will be those, which are representative of the best qualities of the family. Those that are cast out represent the worst features of the flock.
Inbreeding has brought the bad points to the surface.
Continue with this process of segregation, and in due course you will have birds which carry none or practically no faults. Which are of good appearance themselves and are capable of breeding high-class progeny.
Put in a brief and simple way in-breeding produces stock, which is homozygous for its own good properties. Out-crossing more often than not stock, which is heterozygous.
Inbreeding does not create either good points or bad. On it's own does not put anything in, it only makes the best and worst of what already exists in the character of your chickens.
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.
To put actual numbers on the selection process, if you are selecting more than 1 bird in 10 or 20 you are not being a harsh enough critic.
Enthusiastic as I am about in- and line-breeding, they are tools in the breeders arsenal. As is the choice to out-cross if needed to correct a certain failing.
Degree of relationship
I am often asked if there are any particular relationships which I favour. Provided the two birds paired meet as regards their appearance. My preference is never to use brother and sister if it can unless for a reason. I particularly favour half siblings 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.
It is important to understand that the offspring of brother and sister can only have in their genetic composition the characteristics of the two parents reassembled. You are unlikely from such a mating to produce a bird better than either of its parents.
The only reason to use a full related pair is to fix essential traits like the colour of the lacing in my earlier example.
A bird bred from father and daughter can have a double dose of a particular desirable quality carried by the father.
The idea is for the fancier to concentrate on improving one property at a time. Then cover all the points and produce specimens approximating to perfection over time.
You should work to 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.
I have yet to mention the most important skill I have seen in successful breeders is common sense. The secret is not to neglect some aspects of the program in favour of others
How long does it take to breed good birds?
It can take 10 to 15 years and 20 to 15 generations or more to breed good chickens for the poultry show
Patience is needed:
I am going to start this section by saying you be showing your birds every opportunity. A thick skin and experience are two great allies.
Many young fanciers are in too big a hurry to breed many winners. They anticipate establishing a flock of merit within say a couple of seasons.
Whilst you may breed or buy a winner you must not expect to own a strain of your own capable of producing many first prize birds early on. It took me 4 years to obtain my first rosette.
Remember two equal factors:
- The quality of the foundation stock.
- The ability shown by the breeder in selecting and eliminating.
Sometimes we discover that we are the owner of a bird which is exceptional. It may be that you have purchased a single bird from a prize winning strain and wish to preserve it.
For the sake of illustration we will assume it is a hen.
It is completely homozygous for all that is good in the breed of which it is a member.
To preserve the good attributes of the hen we should choose a complementary male.
We then need to produce a selection off offspring and breed the most suitable male young back to the dam to fix the traits we desire.
This can be done for more than one generation if necessary.
The F2 generation will be genetically 75% of the dam.
The F3 generation will be 87.5% dam
A foundation sire or dam can establish a line within his own family by breeding daughters and grand-daughters back to the father.
Or the father’s best sons, grandsons and so on. You should always go back to direct line descendants of the foundation bird on which the line is being established.
In-breeding in practice
The practical application of breeding principles is not too difficult if the breeder exercises common sense. As long as you know your breed exactly as regards the choice of the animals from which he is to breed, and the way in which he mates them.
Better by far have few in numbers of high quality than many inferior specimens.
When purchasing the original stock they will be more useful to the novice than if they are unrelated. Make sure you get enough birds to establish a decent gene pool. You will need at least 3 pairs if you are starting from scratch and preferably 4 or 5 pairs.
The golden rule in mate selection, which applies as much 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.
Never over look that the maxim ‘quality before quantity’
By reason of the fact that they are related they are more likely both to have the power to reproduce their own and their inherited good properties in their children.
It is often desirable to inbreed back to one parent and not the other.
Here is an example:
We have had paired two very good chickens. The cockerel excelling in head and the hen not quite so good. The head is not such a strong feature of her pedigree as it is in that of the male.
Among their young are cockerels and pullets with very good heads, and young males and hens not quite so good in the head.
Even the best of the cocks which are not so good in head must not be mated back to the mother, because they have inherited her weaknesses.
Mate the best of the pullets which excel in head back to her father to effect still further improvement in head. This will also fix the trait so that heads will not be an issue in the future.
The offspring will be homozygous for good heads.
How close to inbreed is a vexed question.
In my own practice if there is very close in-breeding with a pair one season. Father to daughter for instance, I like to mate their offspring to aunts, uncles, cousins, half- brothers or half-sisters in the following season.
This is not a rule but an aspiration. The suitability to each other of the two birds mated is the keystone of my endeavour.
Selection criteria and characteristics:
The quality line
Every year you must set a quality line. Do not breed from any bird falling below that line. If you are breeding for yellow legs as I have been recently with my Barnevelders then you need a specific colour in mind. Get a paint colour chart from the DIY store and set your bar for leg colour.
Every year onward that quality line must be raised higher.
Taking chickens as our example, although the same remarks apply in principle to all livestock. Towards the end of the year when the young birds have moulted the owner should cage all the young stock and their parents. Put each pair of adults into cage alongside them all the youngsters which they have bred that year.
You are now faced with the task of selecting those which he should keep for the following breeding season.
Never keep a chicken to make up a pair. If it is a hen you can make a trio. 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 in a book by leg ring or id before the date of the actual commencement of breeding.
The preliminary list of pairs should be a working list that changes if need be.
When mate selecting the bird breeder should select the best cock and choose for it the best hen, as judged from both appearance and pedigree. Then the second best cock and the second best hen. The process continues until the pairings are complete. My point here is not to average the pairs by putting a excellent male with a fourth choice hen.
Health and vigour:
With breeding of any sort you must take into consideration the virtues of the pedigree and the appearance of the bird and its health and vigour.
Any animal which has ever had an illness. Was a runt or struggled as a youngster or has had a set-back to its development should never be used for breeding purposes. The reason is that inbreeding can fix weakness of constitution if proper precautions are not taken.
Stock used for the laying of the foundations of a strain should not be lacking in fertility. 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 on breeding stock in chickens.
An often expressed but common fallacy is that stock is more capable of breeding youngsters of high merit in their early breeding years than they are when older. Birds are quite capable of maintaining fertility for many years.
Higher hatchability of chicken eggs was reported in spring than in summer (Farooq et al 2003) and the difference was statistically significant. Summer had the worst hatch rates.
Another mistaken idea is that the best young ones are bred at certain times of the year, May and June often being selected as the best months. It may well be that the health of the parents is better at this time of year but genetically the birds are the same. The quality of the birds hatched should be the same even if the rate varied.
In so far as genetics go, neither the parents ages nor date of birth have any influence at all. Rearing chickens on the shortening days in Autumn is likely to cause problems of it's own though.
I tend to pair together either two younger individuals or an older male to a young female. Cockerel seem to have a longer viable period than hens.
in the study of the (EFFECT OF GENOTYPE, AGE AND SEASON ON HATCHABILITY OF EGG - Bang. J. Anim. Sci. 2008) it was noted that birds in the age range 41 to 60 weeks exhibited the highest hatchability whilst hens under 40 weeks of age had the lowest. Hens 61 weeks and above were lower but no where near the levels of the youngstock.
- Does the bird conform to standards. Does it have the right colour, or undercolour.
- Is the chicken well patterned or marked and clear in the lacing pattern.
- Is the breed character correct.
- Head points, body shape and leg colour.
- Is the bird the right size and weight.
- Is the number and quality there and do you have a high discard rate.
- Fertility. to put this in perspective commercial hatcheries have a fertility rate of between 92 and 95%.
- Hatchability: how many dead in shell. No hatchers or malpresentations. again commercially hatchability is 88%.
Do you have strong healthy chicks that hatch easily with no malformations and weaknesses. Malabsorbtion of yolk has both genetic and environmental causes and should be selected against.
Don't breed from birds that have been ill. Worm, keep free of mites and lice, control vermin and treat for coccidicosis.
Self explanatory. If you can help it do not make use of hens that lay shitty eggs or keep clean nests.
Poultry bred by the fancier will have to by definition spend many hours calm in a cage. birds that are agitated may hurt themselves and if a bad tempered cockerel mauls a judge it is not going to go down well. Select for calmness and serenity.
Reducing the risk:
In my own experience, to make an out-cross to bring in several new birds instead of only one, and for this reason:
Out-crossing is at best a risky business—not so risky when there is distant relationship—and it is always possible that the new bird or animal introduced may not ‘nick’ (as fanciers say) with any of the mates provided for him. Your chances of finding, a ‘nicker’ are, of course, increased if you are able to make several out-cross matings instead of only one. When you are able to assess the merits of the youngsters, you may then decide only to continue to work with one of the out-crosses used in the first breeding season, and its progeny, it having given you satisfaction and the others little or none.
The risk can be reduced if the bird or animal comes from a stud you trust.
What is a taint?
Genetically a taint is defined as "a trace of a bad or undesirable substance or quality" or "contaminate or pollute something".
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. But this short-circuiting can be dangerous and in the long term the cause of dismal failure.
The moral for the breeder is this: Never use an animal or a bird, however good it may be in a single property, if it fails abnormally in any other.
It is easier to introduce a taint by in- or line-breeding than by other means. If you introduce a taint you must never in-breed or he will fix that taint even more in one generation.
Successful examples of in- or line- bred stock:
"In Jersey from 1862 up to the war commencing in 1939 it was illegal for cattle of any kind to be allowed on to the island except for immediate slaughter. Consequently there must have been continuous line- or in-breeding. During this time the quality and health of the Jersey cattle improved and the milk yield and the butter-fat content of the milk increased. There was the strictest control by the Royal Jersey Agricultural Society of all breeding operations, and no cow or bull could be used for breeding purposes until it had passed a test for both appearance and pedigree conducted by the society’s inspectors. It will thus be understood that there obtained in Jersey that strict elimination and selection which must be carried out if inbreeding is to achieve its object and not be in any way harmful."
The late George Booth, of Wilsden, Bradford, was a successful breeder of black Rosecomb bantams. In the 1890's he purchased the best trio of these birds then in the country from the late Edwin Walton, of Rawtenstall. From that time up to his death in 1953 he kept the line pure without the introduction of an out-cross. As an experiment he once out-crossed a few birds in this family to an expensive unrelated bird, but not with any success, and he killed the offspring. Of course, I have to admit that to secure such a wonderful result from a foundation of only three birds is somewhat phenomenal—something I have never actually done myself."
Answering the critical:
The critics of inbreeding usually first trot out the story of the human race and the high imbecility percentage in islands and other confined areas where there is much intermarriage. Easter Island suffered not because of intermarriage but because they cut down all the trees.
The social conscience also appears to influence them. The idea of fathers and daughters, for instance, even in birds and animals, bringing children into the world is obnoxious to them. We must dismiss the moral objection as there is no social standard or law in the animal world such as exists in human society. It is a hurdle I had to climb over many years ago myself.
Creatures of the wild mate as their instincts dictate and that is controlled by the one and only law of nature - the survival of the fittest. The health and vigour of wild birds and animals are maintained by the deaths of the weak.
There are those who condemn inbreeding because they have tried it and have failed, and the reason for their failure has been that they have not conducted their breeding operations correctly.
From (Preisinger and Flock, 2000) - "Breeding has resulted in a rapid increase in egg production; in 1930 the average production was 116 eggs per hen per year, whereas
nowadays the average production is increased to 300 eggs per hen per year."
Weather or not you approve of the boiler chicken process or the egg production increases shown above, they have both been made possible by selective, line and in-breeding.
The late Christian Wreidt wrote of the virtues of inbreeding in his book, Heredity in Livestock. (Macmillan & Co Ltd.).
He proved that inbreeding consolidates the good properties by producing birds in greater numbers homozygous for such good properties. A specimen which is homozygous for a property has the factor for it in double dose.
Wreidt also wrote:
"Experiments show that inbreeding in itself is not detrimental, but the genetic factors of the animal used in inbreeding alone determine whether the results are good or bad.’
"There is no sire of any breed so prepotent as an inbred sire."
"By inbreeding it is possible to determine whether a breed contains hidden general defects which will have bad consequences. If a breed has remained sound and strong through several generations of inbreeding there is every reason to believe that there are no defects hidden in that breed."
"By continued inbreeding and careful selection through four to five generations a breed will be found which is constant for those factors selected as a basis, and at the same time free from hidden defects."
"The Mendelian law teaches us that inbreeding results automatically in homozygous constitution."
"The basis on which breeding must rest is the homozygosity to be obtained by intensive inbreeding in conjunction with strict selection."
"Very briefly, inbreeding unaccompanied by selection, brings to the surface all characters, good and bad. Hence inbreeding, plus selection, tends to preserve the good qualities. Owing, however, to the fact that mutations sometimes occur in stock, and to the fact that mutations tend, as a rule, to be harmful, there may be a tendency to deteriorate with which selection inside an inbred stock is not powerful enough to combat and in such cases an out-cross may be desirable."
According to Wreidt, by skillful inbreeding we decrease the number of birds heterozygous for bad properties and increase the number homozygous for desired properties.
Wreidt asserted that the genotype (the genetic constitution) of an chicken can be even more important than its actual shape and colouring. Specimens which consistently produce good offspring (the foundation birds to which I have referred above) even with different mates, and which stamp their excellence upon their descendants are homozygous dominants and such birds are produced by in-breeding, and by continued in-breeding the number of their homozygous offspring is also increased.
Eugene Davenport in The Principles of Breeding: A Treatise on 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."
"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."
In The Basis of Breeding by Leon F Whitney (Fowler Printing Co) when referring to inbreeding says:
"Inbreeding is the great means at the disposal of the breeder to originate new breeds or purify old."
"In the past any breeder might shudder to think of mating brother to sister once. But if we select for excellent traits and discard the weaklings, I see no reason why we cannot secure strains which are not only pure for the traits in question, but which will suffer no harm from inbreeding."
"The great role of inbreeding should be the elimination of undesirable traits and the doubling-up of desirable ones. If young from inbred animals are so weak that they cannot survive, they show beyond a doubt that within the germ plasm of the parents there are genes which, when combined, actually kill the offspring. Therefore, is it not highly desirable to rid the breed of them?"
"I prefer to think of inbreeding as an eliminative process rather than as a strengthening process."