Chicken breeding and genetics.
Breeding chickens is the simple and easy practise of mating pairs or groups of chickens to producing chicks.
Genetics is a hugely complicated subject, often made more so by the fact that it is rarely black or white, there are hundreds of shades of Gray or dominance in the middle.
The well tried and tested rule that most casual chickens breeders seem to adhere to is "Like Begets Like". They lump four hens and a cockerel and a cockerel into a breeding pen with little thought of what they are actually doing. Specimens that lack long and careful pedigree won't give you decent results in the long run.
Table of Contents
- Chicken breeding and genetics.
- Glossary and definition of terms used with poultry breeding:
- Generation notation:
- What is single mating?
- What is double mating?
- The Chickens genes:
- Sex-linked barring:
- Brown eye:
- Silver and Red-Gold :
- Foot Colour:
- Sex-linked white skin:
- Feathering Rate Genes:
- Brown eggshell colour inhibitor:
- Autosomal Genes:
- Rose comb:
- Pied / Mottle:
- Dominant white:
- Frizzle :
- Skin Colour:
- Blue eggshell:
- Pea comb:
- Naked neck:
- Pattern gene:
- Dark brown:
- Duplex comb:
- Multiple spurs:
- Autosomal barring:
- Breda comb-less:
- Recessive white genes:
- Champagne blond:
- Red diluter:
- The E-locus alleles:
- Birchen resembles extended black:
- Partridge (brown):
- Dominant wheaten:
- Recessive wheaten:
- Buttercup allele:
- Ear tuft:
- Long tail:
- Henny plumage:
- Frizzle modifier:
- Recessive melanotic:
- Pink-eye dilute:
- Recessive polydactyly:
- Feathered legs:
- Recessive feathered legs:
- Dominant Rumplessness:
- Recessive Rumplessness:
- Red splash white:
- Recessive black:
- Snow-white down:
- Vulture hocks:
- Dorking white:
- Basic Genetics:
- Inbreeding in chickens:
- The sex of your chicks:
- The sex ratio of baby chicks:
- Feather sexing baby chicks:
- How to breed for a trait for sexing day-old chicks:
- Auto-sexing breeds:
- Lethal genes:
- Genetics of ear lobe colour:
- Genetics of eggshell colour:
- What determines the colour of chickens?
- Mating For Size and Shape:
- Mating tor Colour:
- Mating for Combs and ear lobes:
- Carriage of Tail:
- Shape of Head:
Glossary and definition of terms used with poultry breeding:
Allele -An allele is a gene that is a member of a set of genes that all belong to the same locus, or location, on a chromosome. These genes are often thought of as being related to each other through mutations (one allele could be a mutation of another allele) or they could be mutations of an ancestor gene.
One of a number of possible alternative forms of genetic information at a gene locus . A member of a set of genes that all have the same location on a given chromosome. For example, extended black and birchen are allelic genes ( to each other) because they are both found at the E locus or location.
Epistasis - suppression of the effect of a gene by a non-allelic gene . A gene for trait A somehow having an effect on trait B is an example of epistasis.
Gene - The unit of heredity. A piece of DNA in a chromosome that contains the coded information for a trait. A gene is a piece of DNA that carries information about a specific trait.Gene : An inheritable characteristic attached to the chromosome.
Heterosis - The deviation between the cross and mid parent means . The difference in some property, for example rate of lay, between a cross bred line and the average for the parent lines. For example, ï¿hybrid vigour¿½ can be thought of as an effect of heterosis.
Sex Linkage really only involves the female All poultry carry 78 chromosomes Because the genes attached to the females sex chromosome are only passed on to her sons The genes attached to her singular sex chromosome for the purpose of this exercise are Gold, Silver and Barred (approximately a dozen other genes are known to be attached to the sex chromosome but not relevant to this article All the other genes she carries, which are attached to the other 77 chromosomes she possesses, are passed on in an equal fashion to both sons and daughters.
Autosomal: An autosome is any of the numbered chromosomes, as opposed to the sex chromosomes.
Gametes: A gamete is the ‘sex cell’. In other words it is the sperm of the male or the unfertilised egg (ovum) of the female. In general, the gamete has only half the chromosomes of a mature individual.
Mitosis: There are two types of cell division processes. One process, mitosis, is the division of mature cells in the body…cells that have the full compliment of chromosomes (two pairs of chromosomes).
The prophase is an initial organisation phase in which the ‘centrioles’ (small centres from which fibres originate…small yellow squares in the figure above) form and become organised. In the metaphase spindle fibres emminate from the centrioles and attach to the chromosomes. The anaphase is characterised by the separation of the chromosomes by the spindle fibres and the centrioles…they essentially pull the chromosomes apart. In the telophase the cell wall closes and new cells are evident.
Meiosis: The process of cell division that produces gametes or ‘sex cells’ (sperm and ovum) . The cells that initiate meiosis contain the full set of chromosomes. However, the process of meiosis yields gamete (sperm and ovum) cells that have half that number of chromosomes. Which chromosomes of the original ones find their way to the gamete cells is essentially a random process. In this process, the chromosomes (of the chromosome pairs of the parents) get mixed or ‘scrambled’ in a random fashion. This is also the point at which crossing over of genes from one chromosome of a chromosome pair to the other chromosome can occur.
Dam: The Dam is the female chicken although this term is normally used only when describing hens used in a breeding program.
Sire: The male chicken in a breeding program.
Chromosome: A vehicle for carrying the birds genetic make-up. A chromosome is a string of genes connected together (although most of the chromosome is DNA that has no known function or no genetic activity).Chickens, like people, usually have two of every chromosome. The chromosomes in a chromosome pair are not identical, since one comes from each parent. A gene is said to be dominant when only one gene (rather than two) is sufficient for the expression of that trait to which the gene corresponds. Some genes are referred to as incompletely dominant. The expression of these genes is inhibited by (usually unknown) modifying genes. When the inhibiting, modifying genes are not present, the incompletely dominant gene expresses. This interaction with modifying genes is responsible for the seemingly random nature of the expression of incompletely dominant genes.
The sex chromosomes are unique in that there are two types, a long sex chromosome, the Z chromosome, and a short sex chromosome, the W chromosome. The female has one long and one short sex chromosome, she has ZW sex chromosomes. The male has two long sex chromosomes, he has ZZ sex chromosomes. For this reason, the female has only one copy of some genes that are on the long, Z, sex chromosome.
The genes that are not on the sex chromosomes are called ‘autosomal’ or autosomes. Both male and female chickens have two of these genes. Chickens have 39 pairs of chromosomes (78 individual chromosomes). Most of them are tiny and referred to as ‘dot’ or micro chromosomes.
An important point is that, when we talk about adding or removing a gene, say frizzle, F, we don’t intend that the chromosome is lengthened or shortened by the addition or deletion of that gene. Rather the frizzle gene, F, replaces the gene of the wild-type jungle fowl, f+, when it is added, or, it is itself replaced by the wild-type jungle fowl gene, f+, when frizzle is removed. I used the frizzle gene as an example here, but the statement applies to all genes.
Generation notation - The original members of a mating are referred to as the parental (P) generation.
The first generation of progeny from the parental cross is referred to as the first filial generation, F1.
The progeny of a cross in which one or both of the parents are from the F1 generation is an F2 generation (F1 x F1 = F2) and so on.
What is single mating?
In certain breeds the standard decrees that the characteristics of the male and female should be different, which necessitates double-mating, explained below. Where the standard for the two sexes is practically the same, then single mating is sufficient. By single mating I mean the breeding of both sexes as exhibition specimens from one mating or single pen of birds.
What is double mating?
Double-mating means the mating of two pens, one to produce exhibition cockerels and the other exhibition pullets. This process of breeding has done much to spoil many good breeds, as not everybody has the space to keep two pens. Many poultry fanciers give this double-mating question some hard knocks, but we have only the Club Standards to blame.
When a new breed comes into being, the first desire of the faddists is to draw up a standard that is hard to breed to. They contend that it is better to have a breed that is difficult to obtain high-class specimens of, than where we can easily breed winners. As things are at present, double-mating is necessary in many breeds, and I leave it at that.
In the case of laced varieties, such as the beautiful Gold and Silver Laced Wyandottes, we are sometimes forced to adopt the double mating principles.
Double mating requires setting up a cockerel-breeding pen and a pullet-breeding pen. In the cockerel breeding pen of any variety the male will be a tip-top show specimen and his mates females that are not show birds, but merely breeders likely to throw high-class cockerels when mated to the exhibition male.
The pullets from this mating will, of course, be " duds " and not fit for show purposes. The females in the pullet-breeding pen will all be first-class exhibition birds and the male not a show bird, but a breeder most likely to breed tip-top exhibition pullets. The cockerels from this mating will be " duds " and unfit for the show bench.
The whole modus operandi can be thinned down to this : — The cockerel-breeding male must possess all the necessary characteristics to breed exhibition cockerels, whilst the pullet- breeding male must boast of those characteristics that will go to breed exhibition pullets.
The system is not so complicated as it would appear at first sight and is interesting to follow out, but there must, of course, be many " wasters " in the progeny — whether male or female respectively. In many cases fanciers are satisfied with breeding one sex only and winning honours with same. They specialise in pullets or cockerels, keeping the pullet-breeders or cockerel-breeders only as the case may be. This naturally does not entail so much work as would be necessary if the two sorts were bred.
Homozygous, heterozygous, hemizygous genotypes and phenotypes:
A bird that has one gene, rather than two, for a specific trait is said to be heterozygous for that trait. A bird that has two genes for a given trait is homozygous for that trait.
The genotype is the actual set of genes. The phenotype is the appearance or visual characteristics of what you can see. For example, a bird that is heterozygous (has one gene instead of two) for a given dominant trait may look the same as, or similar to, one that is homozygous (has two genes) for that trait.
They both have the same appearance or phenotype. Because the female fowl have differing sex chromosomes, the long one, Z, and the short one, W, the Z chromosome has gene locations that the W chromosome does not.
Sometimes when referring to these genes that have no counterpart on the W chromosome, the female is said to be hemizygous. Since the female can have only one copy of these genes, there is an apparent overlap in the meanings of 'heterozygous' and 'hemizygous'.
How to predict the outcomes of breeding events for non-sex-linked and sex-linked traits:
Both parents have two genes for a given trait. Let’s consider the gene for frizzle plumage, F, and agree that we will represent the lack of the frizzle gene with f+. The superscript ‘+’ indicates that the gene is present in the wild-type fowl which, with respect to chickens, is the red jungle fowl. Here, I apply the jargon immediately above, but will minimise the use of it from now on. A bird is said to be heterozygous for frizzle if her genotype is (F, f+) and homozygous if her genotype is (F, F).
Since frizzle is dominant, both genotypes will have the same (or similar) appearance or phenotypes. (In this particular case, frizzle shows a 'dose effect' and the frizzle homo-zygote has brittle feathers that usually break off so the homo-zygotes can be almost bare. There is a common recessive modifying factor, mf, that reduces the influence of the frizzle gene.)
To determine the genetics of the offspring, one takes the four possible combinations of the genes of one parent with the genes of the other parent. For example, let’s consider a cross between a bird that has two frizzle genes, homozygous for frizzle, (F, F) and one that is without frizzle, (f+, f+). It helps with the bookkeeping for our purposes here if we (artificially) number the genes: (F1, F2) and (f+1, f+2) so that F1 is the first frizzle gene of the first parent, F2 is the second frizzle gene of the first parent and so on.
The four possible pairs that can be made by combining these genes are: (F1, f+1), (F1, f+2), (F2, f+1) and (F2, f+2). Since frizzle is a dominant trait, these four gene combinations will result in chickens with frizzle plumage (they will all have the same or similar phenotypes). In practice one would not number the genes as I have done in this paragraph. I numbered them to distinguish the four combinations, since they are all genetically the same. One would normally write: (F, F) crossed with (f+, f+) gives (F, f+) times 4.
So, in order to get the four combinations of the genes of the two parents, just take the first gene of the first pair with each gene of the second pair, then do the same thing with the second gene of the first pair. The figure below illustrates how to get the combinations of genes of one parent, (A, B), and the genes of another parent, (C, D). The four possible combinations are (A, C), (A, D), (B, C) and (B, D).
The Chickens genes:Sex-Linked Genes (alleles):
These are the characteristics influenced by the sex chromosome of the chickens:
B - Barring, cuckoo barring. Dominant. Causes white barring pattern in red and black, sometimes used as a black inhibitor, most notably in Leghorns. Cuckoo barring is also an inhibitor of tissue pigmentation and is responsible for the yellow shanks of Barred Rocks. Shanks of females can be darker. Barring shows a distinct dosage effect. B/B gives wider bars than heterozygotes have. Incorporation of the slow feathering gene results in a cleaner, more sharply defined barring.
b+ - Recessive wild-type gene. An allele of the sex-linked barring locus. Lack of barring.
Sex-linked dilution BSd - Females that are hemizygous for BSd (having one BSd gene) have light blue and barred plumage as do the heterozygous males, however, homozygous males show a dosage effect and are essentially white. These homozygous males resemble dominant whites but differ in that they are epistatic to pheomelanin while dominant white is not.
Sex-linked barring B - sex-linked dilution, BSd and the wild-type, b+ are alleles of the same locus. The order of dominance is BSd > B > b+.
br - Not much is known about this gene and there may be a dominant inhibitor of brown eye. Many of the melanin-influencing genes have an effect on eye colour.
dw - Recessive. Males are reduced in size by about 43%, females by 26-32%. Multiple alleles have been proposed. dw is responsible for some beneficial effects. dw homozygotes are more resistant to Marek's Disease and spirochetosis, fewer laying accidents, more aggressive immune response. Abnormal eggs are suppressed (soft-shelled, double yolks). Dwarfism, dw, does not effect mortality but does postpone the onset of lay in pullets up to two weeks. Although egg number and mass are slightly decreased by dw, feed efficiency (feed consumption per egg laid) in laying stocks is usually increased 13-25%.
dwB - Recessive but shows a dose effect; 'bantam' gene. Females reduced in size by 5-11% and males by about 5% in heterozygotes and 14% in homozygotes. Allelic with dw.
dwM - MacDonald dwarf. Reduces body weight by 13.5% and shank length by 9%. Allelic with dw.Dw+ - Wild-type gene. Lack of dwarfing alleles. Allows 'normal' size to develop.
Silver and Red-Gold :
S - This gene is called 'silver'. Inhibits red pigment, pheomelanin. The expression of silver is sometimes affected by hormonal levels and is considered to be incompletely dominant and highly influenced by modifying genes.s+ - This gene is sometimes called 'gold'. Wild-type, recessive. Invokes red pigment.
Id - Light foot colour. Dominant. Inhibits dermal melanin. Reported to have little influence on shank/foot colour in birds with dark shanks due to E/E.
idc - Recessive. This gene allows beak and sometimes plumage pigmentation in dominant white homozygotes.
ida - Allows green spots on shanks - this gene is not widely accepted and the effect of this gene may be due to the interaction of modifiers not allelic to this locus.
idM - Massachusetts mutation. Recessive. Unlike other alleles that belong to this locus, dermal melanin is present in shanks of day-old chicks. Other alleles take more time to express. The darkest shanks are produced in conjunction with E and i+. The combination of idM, E and I produces a pale blue or green colour by about three months of age.id+ - Wild-type dermal melanin. Lack of dermal melanin inhibitors.
Sex-linked white skin:
Y+ - Wild-type gene. Lack of recessive white skin mutation.
y - Recessive, causes white skin. Recessive sex-linked white skin causes yolks to be lighter in colour and reduces xanthophyll levels in blood plasma. This is generally considered to be an inferior trait particularly since the autosomal white skin does not have these side effects on yolk colour.
Feathering Rate Genes:
k+ - Sometimes called rapid feathering. Recessive.
K - Late feathering gene.
Ks - Slow feathering gene.
Kn - Very slow feathering or 'delayed' feathering gene. The order of dominance among the genes allelic to this locus is Kn>Ks>K>k+. The slow feathering gene is believed to be associated with a bald patch on the back of the adolescent bird. The feathers do come in given enough time. Since this is likely due to a dose effect of the slow feathering gene, the homozygous males should be the most likely to exhibit the trait. In my personal flocks, I have both males and females exhibiting this. Many novice poultry keepers wrongly attribute the bald back phenotype with a picking problem.
Brown eggshell colour inhibitor:
pr - This recessive gene results in a lack of protoporphyrin pigment (the brown eggshell pigment) even in hens with polygenic brown eggshell colour. It can be employed to remove undesirable tints from eggs of white shelled strains.
Cp - Short legged condition. Lethal in homozygous state. Dominant.
cp+ - Recessive, wild-type gene. Lack of creeper trait.
R - Associated with poor fertility in some homozygous breeds. Dominant.
r+ - Wild-type gene. Recessive. Lack of rose comb trait.
lav - Recessive. Lavender has been associated with poor feather quality and even lack of feathers in some breeds. Lavender dilutes both black and red; changes black to grey and red to cream. Blue fowls termed "self blue" are normally lavender homozygotes. A mating of two lav homozygotes (blue fowls) will produce blue offspring. Lavender causes dilution by inhibiting the transfer of pigment granules from melanocytes, which produce them, to the feather structure. Lavender expression in homozygotes is present in chicks and adults.
Lav+ Dominant, wild-type gene. Lack of lavender trait.
Cr - Crest feathers are similar in shape and texture to hackle feathers. There may be more than one allele. Incompletely dominant.cr+ - Wild-type gene. Lack of crest.
Pied / Mottle:
mo (pi) - The pied pattern is recessive black and white as in Exchequer Leghorn. Research has shown that the pied and mottle patterns are due to the mottle gene. It is no longer accepted that 'pied' is a distinct gene from mottle, however it is not known why the mottle gene causes the pied pattern in some birds and the typical mottle pattern in others. Mottle causes a white tip at the distal end (end farthest from the skin) of the feather. Chicks with extended black and mottle (E/E mo/mo) as in the Exchequer Leghorn will often have black restricted from the belly and sometimes the head.Mo+ - Wild-type gene. Dominant. Lack of mottling.
I - Incompletely dominant. Influences eye pigment. Inhibits black pigment, eumalanin. This gene is leaky and will allow black specks through. Generally not as efficient at producing a solid white bird as are two copies of recessive white.Heterozygotes of dominant white, I/i+ are often grey with the grey colour visible in the chick down. Dominant white dilutes, but does not eliminate, epidermal melanin.
IS -The smoky gene is an allele belonging to the dominant white locus. Smoky is dominant to dominant white in both chick down and adult plumage in that extended black with I/IS (E/E I/IS)results in grey chick down and adult plumage. Research to date indicates that i+/IS heterozygotes express more the wild-type phenotype with respect to this gene indicating a recessive character with respect to the wild-type.
Smoky is dominant on the chick down of IS/i+ heterozygotes in that down that should be black is grey. The melanosomes resulting from the expression of smoky resemble those resulting from Andalusian Blue. Smoky dilutes black much more than red/gold. An important difference between Smoky and Andalusian Blue is that Smoky in the homozygote state produces a grey/blue bird while Andalusian Blue homozygotes are splash. Therefore, Smoky fowl will breed true.
ID - This gene is often called 'Dun'. Incompletely dominant, off-white. Allelic with dominant white.
i+ - Wild-type gene. Lack of dominant white.
F - Incompletely dominant. The action of the frizzle gene is localized in the feather follicle. It causes a structure abnormality in the feather and abnormalities of internal organs (enlarged heart, spleen, gizzard and alimentary canal) are common.
f+ Recessive, wild-type gene. Lack of frizzle.
w - Yellow skin colour. Recessive.
W+ Dominant wild-type gene. Autosomal white skin gene. Prevents the transfer of xanthophyll into the skin, beak and shanks but does not effect the eye iris, egg yolk or blood serum. This gene is considered to be the wild-type because it is present in the Jungle Fowl.
O - The action of the blue eggshell gene is dominant to the action of the white eggshell gene, o. Blue and brown eggshell genes present simultaneously give a shade of green on the exterior of the egg. The blue eggshell colour permeates the shell while brown is primarily an exterior coating.o - Recessive wild-type gene. Lack of blue eggshell colour gene. Causes white eggshells in the absence of brown eggshell colour genes.
P - Dominant. Sometimes referred to as triple comb. Heterozygotes often display a prominent central ridge with much smaller lateral points.p+ - Wild-type gene. Recessive. Lack of pea comb.
Na - Incompletely dominant. Turkens. Causes bare skin on the neck which becomes reddish toward sexual maturity. Heterozygotes show a small tuft of feathers on the neck above the crop, which is almost missing in the homozygote. The Na allele is associated with increased tolerance for heat, which is probably due to the 30% reduction in overall plumage for heterozygotes and 40% for homozygotes. Na is also associated with a small increase in meat yield and lower body fat content. An increase in embryonic mortality of up to 10% is attributed to Na.
na+ - Recessive, wild-type gene. Lack of naked neck. Allows full feathering.
h - Recessive. The barbs of the feathers are highly modified giving the silkie a 'woolly appearance.H+ - Dominant, wild-type gene. Lack of silkie trait. Allows normal feather structure.
Ml - Dominant. Black intensifier, one of the genes which, in concert with Pg and other genes, is responsible for plumage patterns. There is speculation that there may be more than one eumelanin intensifying gene similar to Ml and non-allelic.ml+ - Recessive, wild-type gene. Lack of melanotic eumelanin enhancing gene.
Pg - Dominant. This is the pattern gene which, together with other genes is responsible for the patterns of plumage. The pattern gene doesn't¿½t seem to express in the absence of Ml in combination with some of the E locus alleles. See text. The pattern gene with the Db and Co Columbian-like restrictors is believed to be responsible for autosomal barring.pg+ - Recessive. Wild-type gene. Lack of pattern gene.
Db - Incompletely dominant. Changes black down of E, ER to reddish-brown. Adults males exhibit a Columbian-type pattern of black, modifies red to orange-tan. Db is a better restrictor of black in males than females.
db+ - Wild-type gene. Recessive. Lack of dark brown-type Columbian restriction.
Dv, Dc - Dominant alleles. The superscripts 'v' and 'c' indicate the 'V' and 'cup' shaped phenotypes and are considered to be separate genes.
d+ - Recessive, wild-type gene. Lack of duplex trait.
M - Dominant. Causes more than one spur per shank on males.
m+ - Wild-type gene. Recessive. Lack of multiple spur trait.
Po - Dominant. Having too many toes. The fifth toe develops on top of the first toe and is longer than the first toe. There are several degrees of expression of this gene.
Pod - Duplicate polydactyly. Dominant to the wild-type allele. An extra toe is present as well as an elongation and splitting of the original first toe. Extreme expression can accompany this gene in which the most extreme cases the entire foot is duplicated.
po+ - Wild-type, recessive. Allows normal foot.
Ab - Non-sex-linked barring. Sometimes called 'parallel pencilling'. This is not a real gene, rather autosomal barring is due to combinations of Pg, Co, Db with eb, ER, and ebc. See text.
bd - Recessive. Birds with this gene are almost completely lacking comb and wattles. Females are considered to be completely comb-less and males have a tiny comb.
Bd+ - Dominant, wild-type gene. Lack of breda comb-less trait. It is believed that this gene is necessary for chickens to produce a comb.
Bl - Incompletely dominant. Andalusian blue-dilutes black: blue pigment is a modified black. Two nigrum genes, E, and one Bl gives a blue chicken; two Bl genes gives splash.bl+ - Wild-type gene. Recessive. Lack of blue eumelanin dilution gene, Bl.
By - Dominant. Abnormally short digits (toes).
Recessive white genes:
c - Thought to give a cleaner white than dominant white. Varieties of White Plymouth Rock, Wyandotte, Minorca, Orpington, Jersey Giant, Dorking, Langshan, Silky and others often carry recessive white genes. Many varieties carry both dominant and recessive white. Allows dark eyes. Pigmentation in chick down varies.
cre - Recessive white allele that allows red eyes.
ca - Autosomal albinism. Alellic with the recessive white genes. Evident via lack of eye pigment. Some melanin present in chick down.
C+ - Wild-type gene. Dominant. Lack of recessive white mutations.
The C locus - The order of dominance among the recessive white alleles is: C+>c>cre>ca. The presence of other pigment inhibiting or enhancing genes will influence the chick down colour. Some adults have a grey colour.
Cb - Dominant. Inhibits pheomelanin (red / gold). The presence of the gene is not observable on the wild-type down
cb+ - Wild-type gene. Recessive. Lack of champagne blond dilution.
Co - Incompletely dominant.Confines black to hackle and tail in both sexes (called Columbian restriction). Thought to cause a gradient in colour from head to tail. Modifies Wheaten to Buff Columbian. Has no effect on extended black, E.
co+ - Wild-type gene. Lack of Columbian restriction. Recessive.
Di - Dominant. Dilutes red, changes red to buff.
di+ - Wild-type gene. Lack of red diluter. Recessive.
Dk - A proposed gene of an allelemorphic series that darkens the shade of red. Pheomelanin enhancer(s). Dkl was proposed for the dark brown Leghorn and dk+ for the wild-type allele.
Gr - This gene may be Columbian, Co, or closely related. This may not be a distinct gene.
no symbol - Recessive, dilutes black to brown/grey.
The E-locus alleles:
E - Often called 'extended black', 'nigrum' or 'self black'. Extends black, changes red to black, red inhibitor.
ER - Wild type.
Birchen resembles extended black:
E, but with non-black breaks on head and hackle. Body is black with some stippling (flecks/dots) of other colour. Used as red inhibitor in Leghorn.
ep, females have non-salmon breast with stippling. Males are wild-type.
Female body varies from light salmon to wheat colour, some black may be present. Males are wild-type.
e+ Wild-type. Female: breast is salmon brown and devoid of stippling, body is black and brown in stippled pattern.
es - Males: black breast and abdomen; non-black hackle, saddle and wings.
Resembles eb but with less pronounced stippling. Males are wild-type ey
Female: resembles dominant wheaten with more coarse black stippling on breast and back. Males are wild type.
Resembles the eb phenotype.
E-locus alleles - The order of dominance among the generally accepted E-locus alleles is: E>ER>e+>eb>es>ebc>ey. The birchen allele is incompletely dominant to dominant wheaten and the wild-type alleles. Additional alleles have been proposed for the E-locus but research to verify these as separate alleles has not been done. As of this writing, the buttercup allele has been sequenced and has been found to be the same sequence as the eb allele. The buttercup phenotype then is due to modifiers or interactions with other genes. Every E-locus allele influences adult female phenotype. However, all the adult male phenotypes are the same as wild-type except for extended black and birchen.
Et - Dominant. Lethal in homozygous state. Thought to be associated with birth defects, particularly in the ear structures.
et+ - Wild-type gene. Recessive. Lack of ear tufts.
no symbol - Black spots and flecks, variable black and white feathers, similar to pied.
Fm -Dominant. Sounds like a disease. The name was suggested by F. Hutt in the 1940s to emphasize the association with connective tissue pigmentation. This gene is responsible for the deep skin pigmentation of silkie. Fm is strongly influenced by dermal melanin inhibitors such as the sex-linked Id mutation.
fm+ -Wild-type gene. Recessive. Lack of fibromelanosis.
Gt, mt - The Gt gene (dominant) allows continual growth of tail and saddle feathers. The mt gene allows certain tail and saddle feathers to be non-molting.
Hf - Dominant. The term comes from 'hen feathering' in which male plumage is indistinguishable from female plumage.
hf+ - Wild-type gene. Recessive. Lack of henny feathering.
ig - Dilutes red. Recessive. A major pheomelanin dilution gene. The gene symbol derives from "inhibitor of gold".
Ig+ - Wild-type gene. Dominant. Lack of cream dilution.
Lg - This is not a real gene. Partridge Rock, Silver Pencilled Rock.
Mb - Incompletely dominant. Characteristic of Ameraucana, Easter Egg Chickens (faux-Araucana)
mb+ - Wild-type gene. Recessive. Lack of beard-muff.
mf - Recessive. Reduces/modifies the effect or expression of the frizzle gene. This gene can modify frizzle heterozygote expression to the point that they are almost indistinguishable from the wild type. Modifies the extreme expression of the frizzle homozygote.
Mf+ - Wild-type gene (uncertain). Dominant. Lack of frizzle modifier.
mi - Enhances black, (helps) change red to black. E + mi gives a black chicken.
Mi+ - Wild-type gene. Dominant. Lack of recessive melanotic enhancing.
mo - Recessive. Makes a white tip on end of feather. Changes a black bird to Mottled and a Buff Columbian to a Mille Fleur. Dilutes epidermal melanin. There may be several alleles corresponding to this locus or non-allelic modifying genes.
Mo+ - Wild-type gene. Dominant. Lack of mottling.
Mh - Dominant. Mahogany restricts eumelanin and enhances the colour of red. Rhode Island Red is a good example. Restricts black in the back and wing of both males and females. Down colour seems to be unaffected by mahogany.
mh+ - Wild-type gene. Recessive. Lack of mahogany.
pK - Dilutes both feathers and eye colour. Recessive.
po-2 - Recessive. A number of extra toes can be present even ascending the shank. Associated with leg deformities, significant decrease in hatchability and much higher post-natal mortality.
Pti-1, Pti-2, Pti-1B, Pti-1L - Dominant. Two different feathered leg loci with perhaps four alleles for the Pti-1 locus (Pti-1, Pti-1B, Pti-1L and pti-1+ : one should always assume the wild-type allele although not always mentioned).
Research has shown that the Pti-1 and Pti-2 genes are most likely not allelic (they belong to different loci of the chromosome). When both Pti-1 and Pti-2 alleles are present, heavy feathering as in Cochin, Sultan, Belgian dï¿½Uccle results. If only one is present, the feathering is weaker as in Langshan, Faverolle, Breda. These genes demonstrate a dose effect. Regarding the Pti-1B and Pti-1L genes, the following is from Somes' 1992 paper in Poultry Science: "The Langshan and Brahma breeds were both shown to possess the same single shank-feathering locus, but because of their differences in phenotype and penetrants in the genetic crosses it was suggested that they possessed different alleles at this locus. This locus was designated as Pti-1, with Pti-1L being the Langshan allele and Pti-1B the Brahma allele. The Brahma allele was shown to be dominant over the Langshan allele. Both the Sultan and Cochin breeds were shown to possess two shank-feathering loci, and the data suggested that one of the loci in the Sultan contained the Pti-1L allele. It is hypothesised that the comparable allele in the Cochin breed was Pti-1B. It is proposed that the second locus in both of these breeds is similar, and the symbol Pti-2 is suggested."
Recessive feathered legs:
pti-3 - The recessive leg feathering gene was identified in a Russian breed referred to as the Pavlov breed. Test mating confirmed the recessive nature of this gene.
Rp - No coccyx (tail vertebra), reduces hatchability.
rp+ - Wild-type gene. Recessive. Lack of dominant rumplessness. Fowls usually have tails.
rp-2 - A skeletal mutation commonly called 'roachback'.
Red splash white:
rs - Recessive. Two copies of this gene give a white bird with splashes of red and black. Chicks are white with a red head spot. This gene may be extinct now. It was first isolated in a line of Rhode Island Reds, but it was not maintained nor has it be re-identified.
sg -Not much is known about this gene. Eumelanin intensifier. There may be a number of genes that play this role.
sl - Recessive. Fowls have no spurs.
sw - Recessive. The chick down is white rather than yellow.
v - Recessive. Long and stiff feathers on the posterior area of the tibia. Characteristic of Belgian Bearded d'Uccle, Breda, Sultan.
wh - Recessive.
wo - Recessive.
Genes on the same chromosome are ‘linked’ and usually inherited together. Two genes that are always inherited together would be linked 100% of the time. However, linkage is never 100% because crossover events occur when the body manufactures sperm and egg cells. The figure below illustrates a crossover event.
The two bars on the left side represent two chromosomes having three genes each. The genes in the middle ‘cross over’ during the process of sperm or egg cell formation. The end result is that new ‘linkage’ relationships exist for the genes on the chromosomes on the right.
Crossover events are actually very common. The rate of crossover events occuring between a gene at locus A and a gene at locus B is proportional to the distance between the two genes on the chromosome (or equivalently, the crossover rate is proportional to the distance between the two loci). A rule-of-thumb for the rate of crossover events in poultry is 1% for every 10 map units in separation between the genes. A map unit is a distance along a chromosome. The actual distance in length units is not really relevant since all chromosome maps are written with distance expressed in map units rather than more familiar units of length.
In the Punnett diagram above describing the gene combinations for two traits, silver and barring, the loci of the genes are linked because they are both on the same chromosome, the Z sex chromosome. This means that the wild-type genes, s+ and b+ genes of the red and non-barred female will be inherited together most of the time. Occasionally a crossover event will occur and the genes will be inherited separately. So, while the Punnett square above gives all the possible combinations of the four genes, it can not be used to determine the percentages that the gene combinations will appear in the progeny that arise from a cross between a male that is a heterozygote for silver and barring and a red, non-barred female.
Since linked genes are inherited together, they can be treated as single entities in the Punnett square. The Punnett diagram below shows the inheritance of silver and barring in the mating of a red, non-barred female and a male that is heterozygous for both barring and silver. This corresponds to the larger Punnett diagram above, but here I consider that fact that the genes are linked and I treat them as a single object:
The results of this Punnett square (the gene combinations inside the square) are what one would get from the mating if no crossover events occurred. The number of times a given gene combination appears inside the Punnett diagram divided by the number of squares in the Punnett diagram is the probability or percent frequency of occurrence of that combination in the progeny. For example, the males are 50% barred and silver and 50% red and non-barred. The females are also 50% barred and silver and 50% red and non-barred. The red, barred male progeny (B b+ s+ s+) that is indicated in the large Punnett diagram above only occurs when a crossover event has taken place, if the parents have the genotype we assumed.
This is an important point, namely that we assumed that the barred, silver male had the B and S genes on the same chromosome. If his genotype had been: Z1 = B s+ and Z2 = b+ S for his two Z chromosomes, the red barred male would have been present in the progeny without requiring a crossover event. The Punnett square for this mating is:
In this mating, half the males are red and barred.
Inbreeding in chickens:
There are varied opinions regarding the issue of inbreeding. One school of thought contends that inbreeding is a negative thing and brings about depression in traits such as fertility, hatchability, rate of lay and others. Another school of thought maintains that the negative aspects of inbreeding can be controlled and even eliminated to a large extent through intelligent selection.
Several studies were conducted in the early part of the twentieth century (for a brief synopsis, see Crawford, Elsevier, 1990, Chapter 39) that showed essentially disastrous results when full sibling fowl were mated for several generations. However, even in the first generation of progeny from full sibling matings in these early studies, traits such as hatchability and rate of lay were seriously depressed. These early studies are largely responsible for many people believing that inbreeding in poultry is universally negative.
Other poultry enthusiasts are aware that inbreeding in plants is a very successful strategy in developing hardy strains with desirable traits. They also recognize that most lines of show-quality poultry are inbred. Research performed in the 1970s and later (see Crawford) on inbreeding in chickens (Leghorns), turkeys, quail, pheasants and partridge fowl showed that desirable traits such as rate of lay, hatchability and fertility can be selected for in inbred lines. These traits can recover from the initial depression due to inbreeding, sometimes even to the same level as the non-inbred lines. A 1988 study by Ameli and co-workers showed that long-term selection against the negative effects of inbreeding can be successful in recovering traits such as high rate of lay and fertility in Leghorn populations.
The depression in traits seen in (random, non-selective) inbreeding, such as fertility, hatchability and rate of lay, is often due to recessive genes. If the depression of these traits were due to dominant genes, the depression would be expressed and observed in non-inbred lines and would not be a phenomenon associated with inbreeding. Epistasis or Epistacy (the interaction of genes at different locations on chromosomes) is sometimes invoked to explain aspects of inbreeding depression.
As of this writing, inbreeding experiments ongoing at the University of Arkansas have associated the greater part of inbreeding depression on hatchability to the male. The evidence for this is the following. Inbred females were mated to a range of different males and the hatchability of their eggs was observed. Inbred males were bred to a range of different females and the hatchability of their eggs were observed. The hatchability of eggs from inbred males was substantially lower than the hatchability of eggs from inbred females, regardless of the cross. So, for example, the hatchability of eggs from a father-daughter cross in which the father is an inbred individual was about the same as the hatchability of eggs from a mating of the same male with non-inbred females. This is strong evidence that the inbreeding depression of hatchability is largely a property of the male birds.
The fact remains that, if the backyard fancier allows inbreeding to take place and does not actively select against the negative effects of inbreeding, the entire population will perform at a lower level with respect to fertility, hatchability, rate of lay and and so on. On the other hand, the objective evidence is convincing that it is possible to develop successful inbred lines of poultry through active selection for desirable traits.
My own opinion regarding inbreeding is that it is an extremely useful tool for bringing out the faults in any chicken.
The sex of your chicks:
The sex of a chick is determined even before the egg is fertilised. Each pair of chromosomes in the fertilised egg has one chromosome from each parent. The father always contributes a long sex chromosome (the Z chromosome) to the fertilised egg.
Before the egg is fertilised, it has only those chromosomes from the mother. If the mother contributes a long sex chromosome, Z, to the unfertilised egg, the chick from that egg will be male because it will have two long sex chromosomes after fertilisation, since it always gets a long sex chromosome from the father. If the mother contributes a short sex chromosome to the unfertilised egg, then the chick will be female because it will have one long and one short sex chromosome after fertilisation. So, in this way the egg can be thought of as already having a sex (gender) even before it is fertilised.
The sex ratio of baby chicks:
On the basis of extensive research, it is now accepted as fact that female chicks are equally probable as male chicks. There is no bias toward one sex or the other. Given good incubation techniques, one should hatch equal numbers of male and female chicks if a statistically valid (large enough) sample of eggs is incubated. However, it is believed that female embryos are preferentially killed by fluctuations in incubation conditions.
Feather sexing baby chicks:
In order for rate of feathering to be an indicator of chick sex, the mothers of the chicks have to have a slow feathering gene (see the table) while the fathers have normal feathering or rapid feathering genes. A cross between these males and females will give pullets with rapid feathering and cockerels with slow feathering. This is a sex-linked trait that can be a sex-indicating trait in the same way that sex-linked barring can.
How to breed for a trait for sexing day-old chicks:
Some common sex-linked traits are Cuckoo barring, gold, silver, slow feathering and dwarfism. Gold, s+, and silver, S, are allelic,which means that they are found at the same locus (on the long, Z, sex chromosome). In order to breed for a trait that will useful for sexing day-old chicks, the trait must be visible in the hatchling. The brown eye trait is not a good choice because chickens don't get their final eye colour until they reach sexual maturity.
To breed a trait that is present in male chicks and absent in female chicks, the trait must be dominant and on the Z sex chromosome (sex-linked), the female parent must have the trait and the male should be lacking the trait. Any of the dominant sex-linked genes listed there can be exploited to give birds that are sexable at a very young age. The silver gene, S, is often exploited in varieties like Red Sex-Links for sexing day-old chicks.
For example, we might choose to cross a red Rhode Island Red male (s+, s+) with a silver Delaware female (S, _) where this means that her long Z chromosome has the silver gene, S, and her short W chromosome is lacking that locus and is represented by an underscore or dash. The four possible gene combinations of the parent genes from this cross are: (S, s+), (S, s+), (s+,_), (s+,_). Here the dominant gene is written first and any gene is written before the underscore.
In this example of the red male mated to the silver female, there are really only two unique gene combinations since two of the four gene combinations are identical to the other two. The 50% of the chicks that inherit the gene combination, (S, s+), are silver males (male because they inherited two copies of the long Z sex chromosome) and are essentially white birds with some possible colouration because silver can be a leaky gene. The other half of the chicks that inherit the (s+,_) genes are red females (female because she inherited the short W sex chromosome).
So the pullets are red and the males are primarily white (yellow down). It is common that Delaware dams and Rhode Island Red sires are used in a cross like this to obtain a Red Sex-Link. This cross is sometimes called Sil-Go-Link for 'silver-gold-sex-link'. The silver gene used this way (the female parent having the dominant gene and the male parent having the recessive genes), will always give sons that have the dominant gene and daughters that do not.
If the cross is carried out the other way, a silver male on a red female, all the chicks will be essentially white if the male has two copies of the silver gene (homozygous for silver). In this case it is not possible to determine the sex of the day-old chicks by their colour.
Any dominant sex-linked trait can be used in this way for the purpose of sexing day-old chicks so long as that trait is visible in the chicks. The slow feathering trait can be a good choice because it does not change the basic colour or pattern characteristics of the birds (see Part III under Cuckoo barring) so that their appearance (phenotype) can be maintained.
An auto-sexing breed is a breed in which the male and female day-old chicks can be distinguished. Some physical characteristic must be observable that is different in males than females. The important difference between a sex-link hybrid and an auto-sexing breed is that the auto-sexing breed is a pure, true-breeding strain and not a hybrid. Hybrids don't breed true in the sense that phenotypes of male individuals are similar to each other and female phenotypes are similar to each other.
An example of an auto-sexing breed is the Barred Plymouth Rock. In this breed, the auto-sexing property arises from the dose effect that the barring gene, B, exhibits. The B gene is on the Z chromosome so the male Barred Rocks have two B genes while the females have one. The males and females hatch with white spots on top of their heads with the male spot being larger and less sharply defined. Also, the females tend to have darker shanks because the B gene is an efficient inhibitor of shank colour. These two traits, based on the B gene dose effect, allow sexing of day-old chicks with a high accuracy rate.
Some genes are lethal. A dominant gene that is lethal when a bird has only one of that gene (heterozygous for that gene) is immediately taken out of the gene pool, since no bird survives with it. Some dominant genes are lethal only when the bird has two copies of the gene. The creeper gene, Cp and the ear tuft gene, Et, are lethal to a chicken with two copies (homozygous). I am aware of an exception to this in which someone claims to have a male with two ear tuft genes that has survived. This should be considered to be a rare exception. The short leg genes in other breeds are often lethal. Some traits, like frizzles and rumplessness are known to reduce hatchability but are not explicitly lethal.
Genetics of ear lobe colour:
Most breeds have red ear lobes. The red colour is due to the blood of the bird and is visible because the skin of the ear lobes, comb and wattles has a rich blood supply that is not masked in any way. These skin areas are so highly vascularized that squeezing a comb between your thumb and forefinger will more than likely squeeze out some of the birds blood onto your fingers. Mosquito bites often leave a small amount of dried blood on the comb. Breeds of the Mediterranean Class (Leghorn, Minorca and Spanish) have 'white' ear lobes.
The white ear lobe is due to the purine pigment which is controlled by a number of genes. The trait is said to be polygenic. The red ear lobe is due to the lack of the genes that invoke the purine pigmentation. Sometimes the white ear lobe can have a greenish or yellowish tinge. The number and location of the genes responsible for white ear lobes is not presently known.
Genetics of eggshell colour:
Brown eggshell colour is a complex trait and as many as 13 genes have been proposed to account for the range in eggshell colour. The white eggshell colour is due to an absence of blue and brown, and perhaps some modifying factors (genes), since there are different shades of white. The blue eggshell gene, O, expresses if it is present which is why it is considered to be dominant.
The gene symbol for the recessive, wild-type gene is o or o+. My understanding at present is that the locations of the brown eggshell genes are not known and it is not known how many brown modifying genes there are or where they are in relationship to the genes of known locations. Brown may itself be just an array of white modifiers. There is a recessive sex-linked gene, pr, that inhibits the expression of brown eggshell genes and can be used to help remove the brown tint from white eggs, for example.
The brown pigment, ooporphyrin, is deposited primarily on the outside of the eggshell and is a chemical compound resulting from haemoglobin metabolism. In fact, much of the brown pigment can be buffed off with a common kitchen (plastic) scrubbing sponge and warm soapy water. The blue eggshell pigment, oocyanin, is a by-product of bile formation and is present throughout the eggshell.
The eggshell colour genes interact in the following way. The effect of the blue gene is dominant over white. The effect of the brown gene is dominant over white. When blue and brown genes are both present, both genes contribute to the eggshell colour making the eggs appear green. In this case, the inside surface of the eggshell will be significantly less green and more blue than the outside surface, which is where most of the brown pigment is.
Since the blue and brown eggshell colour genes should be at different locations, we need at least two pairs of genes to describe the genotypes of the blue, white, green and brown layers. For the purposes of this discussion, I use the fictitious symbol, Br, to indicate a brown eggshell colour gene. I represent the complementary recessive gene that takes the place of Br when it is absent as "br" (lack of brown gene). We can represent the genotype of a blue eggshell layer as (O, O) with (br, br). Blue and white genes, (O, o) with (br, br) also yields a blue egg, but perhaps a lighter blue. The pair of eggshell colour genes, (O, O) with (Br, Br), are the genes for producing a green egg, (o, o) with (Br, Br) produces a brown egg and (o, o) with (br, br) yields a white egg.
Females having one blue gene and one or more brown genes will lay eggs having a greenish colour. My personal experience with eggshell colour makes me believe that this genetics picture of eggshell colour is oversimplified (there are certainly more than one gene for brown eggshell colour. In order to account for the wide range of shades of brown eggs we see in our Sil-Go-Link line, there must be a relatively large number of eggshell colour modifying genes that are not yet known. Most people accept a rule of thumb to the effect that a daughter will lay eggs that are a colour between that of the parent lines.
To explore the genetics of eggshell colour, let’s cross a green egg layer (faux-Araucana or Easter Egg Chicken) with a white egg layer (Leghorn). Here as before, I will use the fictitious symbol "Br" to represent brown eggshell genes. The genes of the green egg layer are (O, O) with (Br, Br) assuming the locations of the blue and brown genes are not the same. The Leghorn is (o, o) with (br, br) for eggshell colour (white). In this example, the daughters will all have one gene for blue eggshell colour and one gene for brown. They will all be green egg layers! My personal experience with eggshell colour genetics leads me to believe it is more complex than this. There certainly must be a number of brown eggshell genes and once you have them, it is difficult to breed them out completely.
What determines the colour of chickens?
All chickens have a ground colour, either Gold, Silver or in rare cases Albino (actually the absence of any colour pigments in the body). The reason some don't appear to be gold or silver is they have other colours super-imposed on them.
That means all hens are either gold or silver. Now the dominant silver gene and its recessive Allele gold, are located on the sex chromosome of the fowl (along with at least a dozen other genes) and the hen passes nothing on to her daughters from the sex chromosome, so she can only pass on this silver or gold gene to her sons. This means that all hens are either gold or silver, but never both.
This is because they only received this gene (either gold or silver from one parent i.e. the cock, remembering the hen passes nothing on to her daughters from the sex chromosome).
The cock birds on the other hand can carry both silver and gold because they receive the gene for silver or gold of both the mother and the father. How does a cock come to be carrying both gold and silver in his make-up? There are 4 combinations which will result in him carrying both silver and gold, and there are 2 combinations that can result in a pure silver cock.
A pure silver cock mated to a gold hen, now all the pullets will be silver as they only receive the silver from the cock bird remembering they receive nothing of the hen bird from the sex chromosome. However all the cockerels from this mating will receive silver from the cock bird and gold from the hen that makes them impure silvers? All these cockerels will appear silver because silver is dominant over gold, but they will have the gold colour hidden in there make-up.
A gold cockerel mated to a silver hen, this time all the pullets will be gold as they only receive the gold gene from the cock bird, all the cockerels though will receive the gold gene from the cock and the silver gene from the hen, again this makes them impure silver cockerels an impure silver cock over a gold hen you would get both silver and gold pullets and cockerels because while the hen will contribute only gold to her sons, the cock will be dishing out both silver and gold to both his sons and daughters,remembering he is impure for silver means 50% of the time he donates a silver gene and the other 50% of the time he gives the gold gene. This is purely a random process (whether or not he gives silver or gold at any particular moment).
An impure cockerel over a silver hen. You can expect both silver and gold pullets but only silver cockerels. This time though you will get some pure as well as impure silver cockerels. This happens because while the hen only gives the silver gene to her sons the impure cock will 50% of the time give gold (resulting in impure cockerels) and 50% of the time give silver, resulting in pure silver cockerels. How do you tell if they are pure or impure? Well while the impure ones will look a little dirtier and perhaps even show a gold feather or 2 in the hackle and tail or shoulder ,the only way you can be sure he is pure is by progeny testing your cock bird. This is done by mating him to a gold hen and if you get just one gold chicken that means he is impure.
Now the other way to get pure silver cockerels is of course to mate a pure silver cock over a silver hen, this will result in all the offspring being pure for silver. This is what anyone breeding silver fowls should be aiming to do (that is to breed only pure silver offspring) that way you don't get any wasters, (i.e. impure silver cockerels.) The pure silver is a much more pleasant colour to look at. Having a lot more clarity of silver, these need to be kept out of the sun as they still tend to go yellow if exposed to too much sun. The impure cockerels although no good for breeding silvers, can be utilized by brown red breeders. They are perfect for diluting the dark mahogany colour that comes from breeding brown red to brown red for long periods of time. They have the effect of lightening the darker mahogany to closer to the required lemon top colour you end up with silver and gold cockerels and pullets, the shade of gold though will be much lighter than the dark gold mentioned earlier. Back to the silvers though, the trick to breeding proper birchins is to get lacing on the breast and striped hackles but retaining the crow wings.
That means no colour other than black on the flight feathers. On the cockerels you also want striping on the saddle hackles and over the cushion and some colour on the shoulders as well. If you mate birds together that are correctly marked, you will end up with very well marked chickens. That is they tend to be a little too well marked on the breast and also you might find that they are no longer crow winged. At least this has been my experience when I used to breed coloured fowls.
The method I found best was to mate a correctly coloured cock bird to a hen with just a little silver in the neck. Mealy greys on the other hand don’t have this problem to the same extent, as you can mate 2 very well marked birds together with success. If you are intending on breeding mealys, be prepared for other colours to crop up as well. I sprung some Columbians and what could best be described as mealy golds, approaching the partridge colour. If you want to improve the type of either of these colours you can use black or white, but I personally would use a white. <
The reason being that once you've crossed the white hen with a silver cock (and you would go that way, remembering silver is sex linked) you can then brother X sister the offspring to find the pure for silver whites This can be done by progeny testing.
These then can safely be crossed back into then silvers in the future, in the knowledge they won't be introducing the gold gene. This is also beneficial for the whites, as whites carrying the silver gene are a cleaner and purer looking white than whites carrying the gold gene, who tend to be a bit creamy, especially the males.
Blacks on the other are better with the gold gene in them as this promotes the green sheen. Columbians are also a silver breed, though I don't have any experience in breeding them as the ones I had came along accidentally from the mealys.
Mating For Size and Shape:
The male chicken seems to exercise a certain amount of influence in regard to the size and shape of the offspring. But to attempt to remedy the deficiency of size in their stock by the purchase of an extra large cockerel is the wrong way to go to work.
In my experience the hen has far more influence over both the size and shape of the progeny than the male has. Take a broad-shouldered, deep-breasted cock and mate with narrow- shouldered hens, deficient also in breast, and the result of such a union will be but little, if any, improvement. Had, however, the tables been turned, and the hens possessed the size instead of the cock, far greater improvement would appear in the offspring.
The male bird does exercise a certain influence. It will be found that by breeding from large hens and a, cockerel deficient in this respect the pullets produced show a far greater improvement than is observable in the cockerels, and it is only by continuing the process of breeding from large hens that the cockerels will far outdistance the original male. There is no question but what the best plan is to have size and shape on both sides, but if a deficiency must occur on one side or the other do not let it be on that of the hens.
Mating tor Colour:
Here we simply intend treating on whole coloured birds, and not with laced, barred, etc., in which we believe considerable influence is exercised by both sexes. It is useless to expect to breed good coloured youngsters from a bad coloured male.
Mate a good coloured black Hamburg with only moderately coloured pullets, and many of the offspring will be excellent in colour, but mate a poor coloured cock with good coloured hens, and both cockerels and pullets will be deficient.
As another example, take a white Leghorn cockerel which is naturally straw coloured, and mate with a carefully bred strain of pure white hens and not a single cockerel will be produced of pure white. If the pullets are in-bred to the father, even the pullets in the next generation will show the straw coloured feathers.
It is of the utmost importance to see that the male bird is of such colour as is required to produce suitable colour in the progeny.
Mating for Combs and ear lobes:
The cock bird has far greater influence over the comb of this progeny than the hen. To breed from a male bird that is defective in comb is, in the majority of cases, to court utter failure, whereas to mate a cock to hens that are defective in comb will frequently produce good results. Ear lobes, in our opinion, are about equally affected by the hen and the cock.
That is to say, the proportion of increase in lobe of the progeny if a large-lobed male is mated to a small-lobed hen is about equal to the effects produced if a small-lobed cock is mated to a large-lobed hen.
Foot and leg feathering, and we would also mention the cushion in a Cochin etc., depends to a greater extent for its production on the male than on the female.
The eye, too, is decidedly more dependent for its transmission to the cock than the hen, and we would never advise a bad-eyed cock being employed for breeding, for personally I have always found them failures, whereas frequently have we produced every chick with good eyes from a bad-eyed hen bird.
In stating this, it must not be supposed that we attach little or no importance to the hen's eye, as such is not the case ; we would advocate the selection of good eyes on both sides; but although in the case of a cock having a bad eye we- would, in the majority of cases, discard him from the breeding pen, yet, if a hen was similarly affected, but otherwise good, we would probably employ her for breeding purposes.
Carriage of Tail:
Here the general tendency is for the cockerels to take after the father and the pullets after the hen.
Shape of Head:
Again, cockerels are more liable to take after the father and pullets after the hen in the shape of the head, but our experience teaches us that the hen has considerably the greater influence of the two.
But this, like many another point, greatly depends upon the pre-potency of the birds. If the bird comes from a good-headed strain, and has been in-bred, more or less, for several generations, the power to imprint his or her likeness on the offspring will be materially increased whereas if he is merely a chance good-headed bird from amongst a number, and is mated with hens deficient in head properties, little, if any, improvement will appear in the offspring.