Pigmentation of the Red Junglefowl

Pigmentation of Gallus gallus

By

Brian Reeder

     To begin to understand the color forms of our domestic fowl, we should first look at their major progenitor, the red jungle fowl (Gallus gallus), and seek to understand the layers of pigments that create the true wildtype, red duckwing color form. Once we understand how the three forms of melanin come together to create that color form, then we can move on and begin to see how the mutations in the domestic fowl redistribute or affect those pigments to create the many color varieties we know.

     The jumping-off point is to understand that there are three distinct forms of melanin present in the wild type red duckwing pattern of the red jungle fowl. The classical term for the red jungle fowl pattern would be agouti, (look at the chick down, which is chipmunk patterned) but that term is not used in the hobby and rarely in the classic poultry research literature. Instead the terms ‘wildtype’ or ‘duckwing’ are used to refer to this expression, which is the MC1R gene known as the e-locus allele e+. The e-locus alleles determine where the three melanins go on the feather areas and how they layer upon each other in any given area. The three forms of melanin are eumelanin (black pigment), sex-linked pheomelanin (the well-known z-chromosome, s-locus genes s+ - sex-linked gold and S – sex-linked silver) and autosomal pheomelanin, which is a different form of pheomelanin from the sex-linked type not directly affected by the s-allele mutations.

     Autosomal pheomelanin is the least studied, recognized and understood of the three forms of melanin, yet this form is present with and distributed by all the e-alleles. It is most prominent and visible on the e-alleles e+ and eWh in the females, but it is present with all the e-alleles and with both sexes. There are no e-allele mutations that suppress autosomal pheomelanin, though E and ER mask this form of pheomelanin under eumelanin (layering). 

While I will discuss autosomal pheomelanin as it relates to the red jungle fowl in this article, it will not be the focus of this article, and will be dealt with in much greater detail in a forthcoming article. I will begin here with Autosomal pheomelanin (Aph). {Please note the change to the abbreviation from my original published abbreviation of Ap. The designation Ap is already used to denote an obscure featherless mutation that is not part of any hobby breeds and thus was a mutation that had never drawn my interest or attention. My thanks to my friend David Hancox for bringing this to my attention!} 

What I will discuss below is a figurative method for understanding the areas of the plumage on both sexes of the duckwing allele e+. This should not be taken to imply that this is meant to describe any developmental processes or melanin studies. This is taken from my own observations of how these pigments seem to be layered into areas. Much of this is observable when other genes remove one pigment or another, allowing the underlying pigments to be seen. For instance when the eumelanin of the tail is suppressed by Db (Dark brown or 'ginger') combined with other eumelanic suppression genes genes on such alleles as eWh or perhaps ER, the pigment that is present in the tail is Aph based pheomelanin with saturation by sex-linked pheomelanin, etc.

Aph is the key to understanding the red jungle fowl’s coloring, as Aph underlies the coloring of the entire bird (see image 1). 

Image 1

There is much misunderstanding about this factor and many people want to call it ‘autosomal red’, thinking the vague references by past researchers to the red shoulder of some sex-linked silver males was a complete description of this factor. It is not, as the red shoulder of males is but one aspect of Aph expression and comes about as an interaction between Aph and mahogany (Mh) and is not the expression of Aph alone. Aph is in fact not red. It is a warm colored salmon/cinnamon toned pigment. The most obvious expression of this pigment, without interaction with other genes, is the breast of unmodified duckwing hens. That salmon breast is the color of autosomal pheomelanin without other coloring genes interacting with it. Aph is NOT effected in any way by the sex-linked silver gene (S) as it is autosomal and not the same pigment. They simply both happen to be forms of a pigment that we loosely call ‘pheomelanin’. This is so important to understand in order to fully grasp how these three pigments work together to make the finished phenotype.

     Next is the sex-linked pheomelanin (see image 2) and on the red jungle fowl this is the wildtype form (s+) gold. 

Image 2

It is important to realize that unmodified gold (s+) is not red. It is an orange tone. To make a red tone from either type of pheomelanin, other genes must modify each type of pheomelanin. In the red jungle fowl on the e+ e-allele the sex-linked pheomelanin is distributed in a dimorphic manner, which means that it manifests differently in the male and the female. On the female, the most obvious area of sex-linked pheomelanin is the hackle, where s+ layers over Aph on most of the hackle (just as it does in the male). The area of the head and hackle with the least expression of s+ is the upper head, the ring of feathers around the face and the lower edges of the hackle down the front of the neck. On the female, the entire back and cushion, much of the shoulder and the wing also express s+ layered over Aph. On the male, we see the expression of s+ in the saddles, but not in the shoulder or upper wing (more on this below). The gene s+ is expressed in the main wing feathers, creating the orange triangle we see when the wing is folded.

     Finally, we come to the third main pigment, eumelanin or black pigment (see image 3). 

Image 3

Eumelanin expression is very dimorphic and is most prominent on the male where it covers the breast and the entire lower body and legs, as well as the tail and sickles and parts of the wing. On the female, we see much less eumelanic expression where it is most prominent on the tail and within the wing. However, there is also eumelanic expression in the center stripe of the hackle and as stippling (small dots expressed as a mild pattern and perhaps the precursor to pattern gene) across the entire back, cushion, shoulder and much of the wing.

    Now, we have seen where the three main pigments are distributed and layered in both sexes, but we are not completely finished, as there are two other factors that modify these pigments to make the finished product in the wildtype red duckwing. The first is dilution of the sex-linked pheomelanin and the second is intensification to red of certain areas of autosomal pheomelanin (this involves dimorphic expression). We acknowledge both of these factors as modifier genes in domestic fowl and call one dilute (Di) and the other mahogany (Mh). However, it is not clear if the two factors in the domestics are exactly the same gene or alleles of these genes, or if the factors in the red junglefowl are actually wildtype precursors to the genes we work with in the domestics. It has seemed to me for some time that my results from numerous test-matings over many years were suggesting that there was not just one form of dilute and mahogany. I suspect that the forms of both of these factors seen in the red jungle fowl are wildtype precursors to the more extreme versions seen in some domestic poultry varieties. However, I do not have enough conclusive evidence to venture naming the variations of either of these factors and suggest that much more research needs to be done on these two factors.

      In spite of this lack of clarity as to how many mutations or alleles there may be of these two factors, I can conclude certain basic points about them. First, it is important to understand that dilute has a strong effect on sex-linked pheomelanin but has very little effect on Aph. Mahogany has little effect on sex-linked pheomelanin unless dilute is absent, but has a great effect on Aph. In fact, you can say that Aph is the platform necessary for the expression of mahogany, because if Aph is suppressed, mahogany does not express in the phenotype (more on this in an upcoming article). It is the combination of Aph and mahogany that results in the phenotypic effect that past researchers have called ‘autosomal red’.

     Now, let us look at how these two factors come together on the red jungle fowl to finish the phenotype (see image 4). 

Image 4

Dilute reduces the concentration of sex-linked gold (s+). The area of greatest dilution is the lower hackle, where sex-linked pheomelanin is most concentrated in the hackles of both males and females. The upper hackle has a lesser concentration of s+ and is not diluted to the same extent as the lower hackle.  The back and cushion of the female show the effect of dilute, though it is less obvious due to the layering of eumelanin as stippling. On the male, the dilution in the hackle is nearly identical to the female and the saddles and wing triangle show mild dilution, though not as much as in the lower hackles. Mahogany layers on autosomal pheomelanin to create deep, rich red areas. This is very prominent on the male shoulder, and while less so on the female shoulder, there will be a mild expression of this effect, obscured somewhat by the stippling and shafting on the female. On the male, there is a slight expression of mahogany on the rear edge of the folded wing triangle and at the forward edge of the saddles. On both sexes there is a strong mahogany expression around the face, on the top of the head, on the outer edge of the hackles and to a lesser extent on the upper hackle. The mahogany seen on the wildtype red jungle fowl does not seem to have a strong effect on the autosomal pheomelanic female breast, unlike some expressions of mahogany seen in domestic strains.

     As can be seen, this wildtype color form is not just the expression of the e-allele. The e-allele determines where the three pigments go and how they layer, while two modifier genes then create visual extremes within the two forms of pheomelanin. It is a very elegant color pattern, designed by natural selection to create a pattern that is broken up and able to blend more efficiently with the natural environment. Solid colors are not efficient for blending into the background, thus we see a complicated layering and shading of the three forms of melanin, with the two forms of pheomelanin being further modified into visual extremes to create an array of shades designed to blend into the background by breaking up the outline of the bird and so help to ensure survival. From this, we can see that the old way of looking at red duckwing as simply e+ s+ is very simplistic and inefficient. For those who are comfortable using the gene abbreviations, wildtype red duckwing would be written as e+/e+ s+/s+ (male) or s+/~ (female) Aph/Aph Di/Di Mh/Mh.

Genetics and Selection

Heritable Traits

The Use of Genetics and Selection in Breeding Poultry

By

Brian Reeder

  In the hobby of breeding domestic fowl, we tend to focus on the issue of genetics as a one-trait/one-gene affair. This is not always the case and linkage can produce what appears to be one gene that is actually several genes coming together and interacting with the chemical pathways of pigment production to make the finished phenotype. Many other factors can combine to make the appearance of a “gene” that is in actuality several genes, linked or not, interacting.  What we do in the hobby when we speak of “genes” is to actually describe heritable factors. A heritable factor is often observed to show a distinct Mendelian genetic segregation ratio. In many case, the heritable factor is likely, in fact, a single gene with a noted dominance or recessiveness.  However, in some cases a heritable factor is not a single gene.  Pattern gene is a noted example of multi-gene interactions involving linkages. We say that there is one pattern gene (Pg). Carefoot showed good statistical evidence that this is so and that there is one major gene, interacting with a handful of other well-known heritable factors or “genes” to produce the range of patterned varieties we see in the modern exhibition breeds. I agree with his assessments. I have however noted that “pattern gene” can show a range of expressions. Some of these are of course examples of various levels of heterozygosity, both for needed factors and unneeded factors that are detrimental to the desired visual phenotype. In other cases, testing suggests that birds can be homozygotes for all the needed genes and yet they do not express that same type of expression. Lacing is a prime example of this. Lacing requires the linkage group of Pg/db+/Ml with Co and preferably on ER or eb. Er birds also require the gene Db, which is in a linkage pattern with Ml and Pg. However lacing ranges from a very fine lace to a heavy, muddy lace on both e-alleles. I have seen cases of lacing that were on the same e-allele and tested at homozygosity for the required genes, but produced drastically different lacing and outcrosses of the two, in generations past the F1 tended to segregate into one type or the other; fine laced or heavy laced. Are we seeing two different alleles of Pg? Two different genes completely that do very similar things, or perhaps we are seeing the effect of another gene such as a melanizer or even a factor that merely modifies the expression of the lace? Could there be a factor that changes the expression of Pg at some point in the developmental pigment pathway? I don’t know, but there are clearly such differences across the entire expression of the heritable factor Pg and my observations suggest that the differences are in some way heritable, and segregating, as one would expect for a Mendelian gene. Such questions are fascinating and may in time be answered.

     In the hobby, we would seek to test mate to produce statistical models of segregation pattern. We then name a gene, using our statistics to prove the unseen presence of a strand of DNA somewhere on a chromosome. This is the research model of one hundred years ago. It is usable, as far as it goes, but it may be a poor model for naming and designating genes. It is more attuned to diagnosing heritable factors. Heritable factors may not always have a basis on a one-gene/one-trait scenario. However, that does not mean they are not useful.

     In the real world of laboratory research, where actual genes (groups of DNA base pairs working in unison to produce specific proteins) are mapped and traits linked to such, we see a real capacity to name a “gene”. When they say that they have mapped the gene, they mean that literally. In the hobby, when we say that we have discovered a gene, we have actually observed a heritable factor. Beyond really large and long range data collection using huge numbers, it is not very credulous to put too much faith in the small numbers we work with to definitively declare a “gene”, because we in no way have observed such. With that said though, the observation of a heritable pattern is still useful and factual. A hobbyist doesn’t need to know where the gene is or the designation given by the scientists who have mapped a given gene. What the hobbyist who wishes to pursue any given phenotype or trait needs to know is heritable probabilities. Some factors have very good statistical data to confirm that they are truly a gene, in the literal sense, and in some cases, our friends in the laboratory are showing us where those genes actually are in the DNA. To me, this is extremely fascinating and engrossing. I suspect that in time, such research will become extremely useful to the hobbyists of the future. I just hope I live to see the hand held chicken egg scanner that tells you if the embryo is alive and its entire genetic structure so you can decide whether to set the egg or not. I visualize it looking much like a tricorder from Star Trek, or perhaps even as an app for your Iphone. Until then, however, for the most part, we rely on observed and observable data concerning heritable traits. There is probably a high correlation between observed traits and DNA segments, but the important part is to understand how the factor behaves and if it is a simple factor or a complex factor. The former can be followed with a simple Mendelian ratio while the later requires a quantitative approach.

      So how does the hobbyist apply the gathered knowledge of domestic fowl heritable factors? They decide what traits they are selecting for, first and foremost. Most will focus on color, while some will focus on form and a few will work on more intangible traits. The first step is to really, honestly, assess where you want to focus and then make a list of the traits that are most important. Here is where you are going to focus. However, it is not impossible to give a large range of traits some consideration. I would respectfully suggest that everyone could benefit their birds and themselves by selecting for hardiness and heritable disease resistance. Some deeply inbred lines could use an outcross here and there to something that isn’t nearly as bottle necked as they are. Aggressive birds are not always a joy to work with and birds with poor egg production make reproduction difficult and the possibility of a bottleneck become that much higher. If we first remember that no matter which “breed” we are working with we are breeding domestic fowl, then we can select for a healthy and functional domestic fowl as well as the traits that make it the given “breed”.

      Selection for many traits requires a quantitative approach. Select a few traits that are most important to you and these are given the most emphasis, scoring higher in your evaluation. The absence of said traits can be cause to eliminate a bird if the heritable factor is generally dominant. The absence of a recessive gene in the phenotype can still make for a useful breeder, if it is a heterozygote for the gene. However, do not stop there and note a whole range of factors so you can know your line. Evaluate it honestly and when all else is equal in your priority traits, select the individuals with the best secondary traits on your list. In each generation, your goal is to merely increase the presence of as many of your selected traits as possible. The actual increase can be small, perhaps only five or ten percent, but if you are seeing any percentage of increase in trait expression then you are making progress on the population as a whole. That is how you form a strain. A strain is a highly selected line of relatives. They produce recognizable combinations in most instances. On the level of selection for heritable traits, concentrating the selected heritable traits into high expression in the phenotype is the hallmark of a ‘strain’. This also implies high levels of homozygosity for the heritable factors, such as genes, gene combinations, or other modifying interactions that may affect the phenotype.

     The key to fast progress in heritable trait selection is to obtain very homozygous stock from a strain or to work with large numbers in order to apply selection pressure to increase the homozygosity for the targeted traits. The smaller the number raised, the slower your progress may be. However, even when working with small numbers, selection albeit limited, can still be applied. Genetic knowledge can be of great use to the person who can only work with a small number of individuals but wants to create some type of advancement with their stock. The best advice I can offer is to look for very hardy, fertile lines with good production and temperament and then bring in traits from outside of that line where needed through outcrosses to create your target phenotype. If you can find a strain with good domestic fowl qualities and expressing highly bred phenotype traits, they are jewels of great value and can both be bred as-is and used in improving other lines with similar heritable traits.  There are a few well know varieties of certain exhibition breeds that are noted for being very well bred, with many good traits combined. They usually aren’t the most ‘fru-fru’ and frilly, but they are very good, sound birds that are a joy to work with and can be used to reinvigorate a great many breeds that share one or two major traits in common. When using this technique, a working knowledge of heritability traits can be valuable.

Silhouette

Brian Reeder

An Overview

The silhouette is the outline of the bird. It is a solid black image that focuses attention on the outline of the form.

The definition of ‘silhouette’ from Wikipedia is: “silhouette; the image of a person, an object or scene consisting of the outline and a featureless interior, with the silhouetted object usually being black. Traditionally, a silhouette is a form of artwork, the term originating in the 18th century and applied to portraits or other pictorial representations cut from thin black card.”

In poultry breeding, we use the silhouette to understand how the various traits we are selecting for in our lines create a unique outline, recognizable when completely devoid of detail.

All the classical exhibition breeds are recognizable by silhouette alone if you have much experience with poultry at all. A glance at the silhouette of a Polish makes self-evident what is being indicated, and so too with the Cochin or the Japanese Bantam. Each of the junglefowl shows unique and discernable silhouettes, and while some Asian Game strains are called jungle fowl, their silhouette makes it immediately apparent that they are not really jungle fowl at all, but very modified domestics.

When lines are well selected for the expression of their target form genes, combinations occur that are very recognizable, once you have some familiarity with the breeds either through maintaining them or seeing them regularly at shows.

The common denominator is the silhouette, the outline of the bird, regardless of any factors. Certainly, some recognizable color varieties immediately tell you what you are likely seeing, such as mille fleur, but the D’Uccle is recognizable based on its outline rather than only one of the breeds many color varieties.

There are instances of overlap with some breeds. Some bantam Cornish might be hard to tell apart in silhouette from some Japanese Shamo bantams while some of the simple formed breeds, being jungle fowl like in form, can be harder to tell apart in silhouette unless you are very familiar with them.

Many of the American breeds are very similar in silhouette, but this should come as no surprise as they all have common ancestry through Chinese fowl imported in the mid to late eighteen-hundreds.

These again can be harder for the un-experienced to tell apart. However, a Rock and a Cochin are not mistakable for the other and are immediately distinguishable by their outline, and neither would be mistaken for an Onagadori, whose silhouette is vastly different from the other two. So how can we begin to understand how the Genes of Form and Feathering come together to make the silhouette?

Silhouette as Composite of Form and Feathering Traits

Three groups of heritable factors come together to make the silhouette: skeletal, muscular and feathering. This is not to imply that any of the genes within any given group is related in any way, only to put them into three easily recognizable groups to make our purpose of understanding the silhouette easier. The subject of the genetic factors of these three categories is complex and some of these factors are quantitative in nature.

With the release of my latest book, ‘An Introduction to Form and Feathering of the Domestic Fowl’, I have documented many of these factors. I have classified the heritable factors I discuss by the three categories that make up the silhouette; skeleton, muscles and feathering with the comb-type crowning the silhouette. I will list here from the contents some of the genes I discuss in the book that relate directly to the silhouette.

Genes of Form and Feathering

Skeleton

Wild Type

Extension

Shortening

Horizontal/Vertical

Tail Bud, Tail Angle and Taillessness

Polydactyly

Muscle

Wild Type

Muscle Increase

Muscle Decrease

Feather

Wild Type

Fast and Slow Feathering

Feather Shortening

Feather Lengthening

Feather Count

Feather Thickness

Hen feathering

Leg Feathering

Vulture Hocks

Tight and Loose Feathering

Hookless

Frizzling

Crest and Tuft

Muff and Beard

Ear Tufts

Nakedness

Comb and Wattle

Single Comb

Rose Comb

Pea Comb

Duplex Comb

Buttercup Comb

Composite Combs

Comb and Wattle Size

As you can see, there are many heritable factors involved in the three categories that make the silhouette. The discussion of those genetic factors is too long for this article, but we can briefly consider the three categories and how they come together to make the silhouette.

Building The Silhouette

The skeleton is the structure upon which all else is based. The skeleton genes will determine how everything else is distributed. The muscles are arranged upon the skeleton and it is the skeleton that determines the plains of the form, the angles that determine the kinesthetic orientation and the center of gravity.

Skeletal genes can make a shortened form with short extremities (neck, legs, etc) and a forward tilted orientation wherein the center of gravity is to the front of the body, or skeletal genes can make a vertical form with long extremities and the center of gravity directly over the legs.

These are but two extremes and a wide range of phenotypes are seen in between them. The wildtype skeleton of the jungle fowls is generally horizontal with the center of gravity to the center of the body, just in front of the legs, over the front toes. When excited, jungle fowl may raise the front part of the body and the center of gravity shifts back slightly centering over the legs. When they travel in brush they drop the front of the body down and the center of gravity shifts forward slightly. The three major stances of jungle fowl are exaggerated in the many phenotypes seen in the domestic fowl. These variations all originate in the skeletal genes.

Once the skeleton is in place, the muscles layer on the skeleton and fill out the form. The level of muscling, either increased or decreased, fills out the body of the bird.

To get a good idea of how muscling can change the form, think of this progression; Modern Game - Jungle Fowl - Cornish. The jungle fowl represents wildtype while the Modern Game is muscle decrease and the Cornish is muscle increase. These two variations on wildtype are quantitative, so this is not a case of two simple genes. It is also important to bear in mind that feathering can disguise muscling. Loose feathers on decreased muscling can mimic muscle increase. Extremely profuse breeds such as Cochin may appear robust, but this is too often not through muscling. The surest method to determine muscling in any bird that is not tight-feathered is to simply handle the bird. Marek’s Virus can cause muscle diminution and this can often be mistaken for muscle decrease as in Modern Game.

It is not the same and many breeds that are small or profusely feathered show the effects of Marek’s that shouldn’t. Marek’s virus is common in our poultry but recent research shows there to be several variations of genetic resistance for Marek’s, so selection for resistance can eliminate that form of undesirable muscle diminution.

Feathering is the glory of our fowl. Feathers define birds. There are many feathering genes in our domestic fowl. The most important and fundamental variation is tight, hard feathering and loose, soft feathering. The subject of feathering in the domestic fowl is complex and there are several quantitative factors.

Since it is such a large topic, it is impossible to discuss here, but I cannot stress enough how vital the feathering genes are to the finished silhouette. Just image what a Cochin might look like with no feathers, as compared to what a Cornish would look like with no feathering. Finally, the comb genes make the crown that sits upon the head of the silhouette. While the comb is a small point in the overall silhouette, it is the finishing touch.

Applying the Silhouette to Breeding

Silhouettes are easily made in any paint program. I use a free version of Gimp. Using a picture of your own bird in a side stance, use the paintbrush to white out the background and then blacken in the bird. You may need to increase the screen image size at times and you will need to use variable sizes of the paintbrush, but it is very easy to do. Once you have turned your bird into a silhouette, find or make a silhouette of show winning birds or standard images.

Compare your bird’s silhouette to the standard and/or exhibition winners. In this way, you can find the weak points in your bird’s overall form and aim your breeding toward correcting the problem areas. It is very helpful in selecting birds for phenotype to become acquainted with the desired silhouette as well as the silhouettes of your own birds. This can be an invaluable tool in selecting toward the desired type in any breeding endeavor. It is also a wonderful way to step back from color selection and consider the form. I hope you try making your own silhouettes. I believe you will find it a useful tool in the breeder’s toolbox.

Press Release: An Introduction to Form and Feathering of the Domestic Fowl

Press Release: An Introduction to Form and Feathering of the Domestic Fowl

Sunday May 22, 2011

An Introduction to Form and Feathering of the Domestic Fowl
By
Brian Reeder

This informative new volume is the second release in Mr. Reeder's series of guide books to breeding and genetics. Specifically dealing with the Domestic Fowl, the ubiquitous chicken, this volume deals with form, complimenting the first book in the series, 'An Introduction to Color Forms of the Domestic Fowl'.

In this introduction to the genetics of form and feathering of the domestic fowl you will find a straightforward method that allows anyone, beginner or advanced hobbyist, to understand how the major genes of forms and feathering come together to create the silhouette that is the hallmark of each breed. Beginning with a discussion of the skeleton genes, then moving to muscling genes, feather genes and finally to comb genes, an understanding of the layers that make the silhouette is revealed. From this system of understanding how the silhouette is formed, one can then understand what really makes one breed unique from another.


All of the genes presented herein are found in the commonly seen exhibition breeds and many hobbyists will be familiar with these breeds, but may be less familiar with the genetic factors involved. This volume is a wonderful tool for learning the basis of how the breeds are made, how their respective forms are derived from separate genes of form and feathering, and how those genes all come together to make the form of any given breed. Many genes are required to derive each type and the combination of those many genes creates the silhouette. As you will see from the many silhouette illustrations on this book, once you know a breed, it is instantly recognizable from the silhouette alone.


In addition to the discussion of the genes, there is a discussion of basic genetic concepts and of the complex and often confusing method of quantitative that is very applicable to many of the genes described herein. This book presents a very clear system for learning about the genetics of form and feathering in the domestic fowl and is written to be understood by the young and beginners alike.

Available at Authorhouse.com and Amazon.com

An Excerpt from the newly released... 'An Introduction to Form and Feathering of the Domestic Fowl'

Quantitative Traits and Selection Methods

By
Brian Reeder


Quantitative traits are common in the phenotypes of domestic fowl. Unlike qualitative traits that produce the classic 1:2:1 pattern of inheritance, quantitative traits vary over a continuous range and are the result of alleles of two or more genes. Large numbers of birds are needed to select for traits of a given preferred combination. In observing a group of birds, one should note the range of expression of a given trait. As an example, let us consider the single comb for a moment. When I say single comb, we all have a basic agreement about what that word means. It is a blade comb, flattened with triangular teeth or points at the top row. In this basic regard, the description is exact, but we all know from observation and experience that the expressions of the single-comb can range tremendously. Combs can be huge and tall and very thick, or they can be large and thin, flopping easily and very susceptible to frostbite. There are tiny single combs that are thick and tiny single combs that are very thin in width.

Some single combs are rough while others are smooth. The numbers of points varies widely as does the exact size and shape of the points and the blade section on the back. Folds, lines, creases and many other strain-specific traits are also seen on this comb type. Some lines of single comb birds are deeply homozygous for their phenotype expression and their single comb expression breeds true and may be very prepotent in outcrosses. Other lines are segregating for a given number of traits and so their single combs are not of one consistent form. Consistent gene expression in the phenotype implies homozygosity for the alleles in question.

As an example, let us say you want to make a small thick comb that does not get frostbite. You have set out a parameter for a trait that may represent more than one gene. You begin by selecting those birds that express the individual traits you want to combine as well as those that are coming closest to the ideal expression.

As you blend each generation, you are looking for intensifications of traits as well as further recombination, working to bring all traits together as homozygous in one population. In each generation you will be looking for an increase of percentage in the given areas of selection, with an eye toward a total increase of multi-trait expressing individuals.

In our single comb example, you would note and select those with rough combs, small combs and thick combs. Those that had two traits combined and those that had three traits combined would also be noted and they would be given some level of preference. Multiple mating schemes could then be employed for both blending traits to get the multi-gene recombinant homozygotes and for intensifying the expression of homozygosity in recessives in general. Each generation should show an increase in the desired traits if your matings are well planned and you know what you are looking for. Each population or line within the over-all group is scored for every trait in the set of traits being selected for. In this way, the percentages of increase for any trait can be gauged in each line of the population.

To manage quantitative selection you need to pay attention to trends in the population. Those birds that show the greatest expression of desired traits are the most likely candidates to further express the trait and for enhancing expression into a more extreme (homozygous for a very specific combination) expression. This is easily done when the background genetics support the expression of the desired traits, especially if many or all of those traits happen to be dominant factors, making their early expression more obvious. Selection for major phenotype groups of factors may actually be practicing some level of selection on many, many more alleles than the simple explanation of single gene traits would imply.

With recessive genes or when both dominant and recessive traits are involved, the production of homozygotes is necessary to see the recessive effect. This can make selection more difficult. In the case of a recessive trait, pedigree is much more important, as recessives cannot be seen in the phenotype. Thus, you may find yourself frequently working with generations that do not express some or all of your desired phenotypic expressions.

The recombination of phenotypic expression in a multi-gene recessive scenario is difficult and requires a multi-pronged approach, patience, good record-keeping, large numbers of birds, and a focus on homozygotes. In this instance, we may only see very small incremental increases in gene expression for the total expression of all involved alleles for several generations. Yet, as later generations reach high expressions of homozygosity, the numbers will tilt and the population expression will begin to be set and express in high percentages.

In summary, quantitative selection is picking those that look the most the way you want them to look and selecting in that direction each generation. You may need to be patient if you are working toward expression of a large number of recessive traits. With dominant traits, you may get faster results due to being able to visually identify heterozygotes. Select for those birds with the most traits you want and as you see some increase (even if just a five or ten percent increase per generation) then you are heading in the right direction.