Chocolate Sables - Chocolate Shaded Genetics

With chocolate Lionheads continually gaining popularity, there is increased interest in the variety as well as the color crossing rules that go with it.  Having been raising chocolates for many years, the single biggest issue I regularly see in the variety is the presence of the shaded gene, often unbeknownst to the owner.  What happens if you cross your chocolates and shadeds or if your chocolates already carry the shaded gene?  What if your chocolates ARE shadeds and you didn't even know it?  This article will go in depth on this subject, mainly focusing on chocolate sables in particular, and I will discuss how to identify chocolate sables in a litter, walk you through the developmental changes in appearance as they grow, and outline ways to both identify and breed out the shaded gene from your chocolates.  Some knowledge of rabbit color genetics is helpful for better understanding of this article, but as always, if you need me to explain something further, feel free to contact me.

What do chocolate sables look like?

While I have test bred my main chocolate program and know my animals do not have the shaded gene, whenever I introduce new bloodlines, I am always careful to test breed for shaded and have had it pop up a few times in these situations.  In this example, I actually raised a litter that contained chocolate shadeds for a friend.  The mother was a REW that carried chocolate and the father was a chocolate that carried shaded.  She came to me bred and I never saw the sire, but it is possible he was actually a chocolate sable himself based on the kits that he produced.  

Here are the kits as newborns.  There are two chocolate sables and a siamese sable, although at this young age, it is hard to visually confirm color. 

 

Here is the litter again at three days of age.  This is a critical age to watch color development.  If there is one trait that is trickiest about shadeds, it is that they CHANGE as they grow.  Since self chocolates do not change shade as they grow hardly at all, a change is something to watch out for as an indication of shaded.  At this stage in development, you can see that they are chocolate-based, but they do not look like self chocolates having a lighter brassy tone to them.  Between about 3 and 10 days of age, I find you can more-easily notice the difference in color. The kit in the center is the same shade as the one on the right, but the light hit them differently, so this also demonstrates how much lighting in a photograph can effect how a color looks.

 

Here they are again at about 8 days of age.  This color comparison is a great example of the effect of the shaded c(chl) gene.  On the left is a black above and a siamese sable below; the only difference between them is the c(chl) gene in place of the full color C gene.  Genetically, a siamese sable is simply a black with the shaded gene.  The shaded gene weakens the eumelanin pigment expression to more of a brown and creates shading with darker points and lighter body color.  On the right is a chocolate above and a chocolate sable below.  A chocolate sable is simply a chocolate with the shaded gene and the brown eumelanin pigment is also weakened.  Since brown pigment looks much less intense when compared to black pigment to begin with, the weakening of the expression is much less noticeable and sometimes very hard to distinguish at all. 

At this stage, the difference is noticeable enough, but it becomes much less so for chocolate sables as they mature. 

 

 Here the litter is again at 9 days of age.  They are already looking more like self chocolates and soon will be almost indistinguishable. 

At 3 1/2 weeks of age, the chocolate sable kit on the left looks just like this self chocolate kit from another litter on the right.  Another important aspect to consider is that in dilute form (lilac versus lilac sable), these differences will be even harder to distinguish as well as in homozygous shaded form (chocolate versus chocolate seal or lilac versus lilac seal).  

 

With open eyes though, there is something important to look for that will last through adulthood.  Many chocolates have a bit of a ruby cast to their eyes, although some do not.  Shadeds also have this ruby cast that is usually stronger.  When combined, chocolate shadeds get a "double-dose" of ruby cast and have a VERY heavy ruby cast to their eyes.  This ruby cast can be described as a reflective and transparent red "film" over the pupil that becomes more or less noticeable depending on how the light hits it.  It looks similar to what is seen in pictures with flash when photographs have a "red eye" only this is seen with the naked eye.   Ruby cast is also VERY hard to photograph, so I had much difficulty attempting to document this effect for this post.  The pictures below capture it pretty well, but it is much more noticeable in person. 

 Here is an older chocolate sable doe picture courtesy of South Dixie Rabbits.  This and the pictures above were taken without flash so the true ruby cast is showing, although hard to capture accurately on camera.  You can also see some shading in this animal (the ears and face are a bit darker than the rest of the body).  Shading in chocolate-based animals can be very hard to see and not all chocolate sables will display such noticeable shading. 

Another phenotypic aspect to take note of is the color of the eye itself in addition to the ruby cast.  Chocolates and chocolate sables will both have brown eyes, but the shaded gene in chocolate sables will also weaken the brown color of the eye.  This in combination with the extreme ruby cast can create an unusual effect that is sometimes described as purplish or even olive and is visible in this picture (note that the lighting washed the body color out excessively, but the eye color appearance is accurate.    

Another form of chocolate shadeds is the recessive non-extension form, chocolate point.  A chocolate point is to a chocolate sable as a chocolate tort is to a chocolate.  In non-extension form, shaded in chocolates is super easy to identify as the rabbit pictured below would be hard to mistake with a chocolate tort (see end of article for comparison).  Picture courtesy of Victorian Hills.  I highly recommend using non-extension colors in your chocolate program because of how easily it can express the presence of the shaded gene.  Chocolate points will also express the extreme ruby cast in their eyes.  

I have shaded in my chocolates, now what?

Now that you can identify a chocolate sable, what is the next step?  For most people, it would be to breed out the shaded gene from their chocolates.  Shaded and Chocolate do have a place working together in a chocolate point breeding program, but this is best kept separate from a self chocolate program due to the effect on coat and eye color that can be (and is often!) regularly missed.  While chocolate points are easy to identify (and are very beautiful!), the full extension versions (chocolate or lilac sable and chocolate or lilac seal) are difficult to identify and thus destructive to a breeding program.  Unless you are working with a separate chocolate point breeding program, I highly recommend not combining chocolate and shaded.  Once you have established that you have the shaded gene in your chocolates, you can work to breed it out.  Breeding shaded out is not too difficult with the right rabbits. 

There are three genes that are very helpful to weed out shaded and those are REW "c" on the color locus, tort (non-extension) "e" on the extension locus, and black "B" on the base color locus.

The REW gene is what should be used to actually breed out shaded because it is more recessive.  The tort gene is extremely helpful for confirming in an obvious visual way that an animal is or is not shaded itself.  And finally the black gene is helpful because black based shadeds are easier to identify than chocolate based ones (i.e. a siamese sable is obviously not a black, but a chocolate sable may look just like a chocolate).  

Especially if you are newer to chocolates or don't necessarily know the genetics of your program inside out, I very highly recommend that you breed torts and REWs in with your chocolates and keep the genes in your program.  A bonus is that you get chocolate torts which are showable and very beautiful.  Carrying tort or REW does not change a self chocolate's color at all, so there is no color damage to worry about with these genes assuming the animals don't carry random other problem genetics like stray white hairs.  

How tort works at identifying shaded in a program is quite simple.  A chocolate with the shaded gene is a chocolate sable (hard to ID), but a chocolate tort with the shaded gene is a chocolate point (very easy to ID).  Not only does the shaded gene weaken eumelanin pigment (black or brown pigment), but it completely "bleaches" pheomelanin pigment (red/orange pigment) which is visible in non-extension form.  A chocolate tort's body is a firey orange while a chocolate point's body has all that orange pigment "bleached" to white.  Visually, this is very easy to distinguish.  For this to work, the chocolate/chocolate sable parent needs to carry tort (non-extension) and the tort parent needs to carry REW.  It may take a few generations if your chocolates don't carry tort.  

Chocolate Tort doe showing lots of orange pigment

Chocolate Point doe showing all the orange pigment "bleached" to white - picture courtesy of Victorian Hills

 When you have established that you have the shaded gene in your chocolates and want to breed it out, this is where REW comes in.  It is impossible for a REW to carry shaded, so REWs are always guaranteed to be "clean".  If you have a REW out of chocolates so it is genetically a "white chocolate", these are perfect so that you do not need to try to breed chocolate back in after breeding out shaded.  Chocolate torts that carry REW are also guaranteed to be free from shaded because if they were c(chl)c, they would be chocolate points which is obvious to tell apart.  If you have nice chocolate sable rabbits in your breeding program and want to eliminate the shaded gene without losing the line, breed in REW and save REW babies which are guaranteed "clean".  If you have chocolates with normal eye color, but suspect they may carry shaded, breed in REW and then the babies are guaranteed to carry REW, so you know what the recessive gene is that is carried and can focus on identifying the phenotype.   

REWs and Chocolate Torts that carry REW are always "clean".  These are very valuable in a breeding program to clear out unwanted genes!

Are there any other genes to watch out for that act similarly?

What if you are getting chocolate point kits, but you never see this extreme ruby cast that I have discussed?  What if the eye color in your chocolates is "strange", but there is no ruby cast?  While shaded is very destructive to a chocolate breeding program, the chinchilla (chin) gene is even worse and I will explain why.  Visually, a careful eye can identify a chocolate sable by looking for excessive ruby cast and possibly noticing shading in color.  The chin gene can interfere with both these cues as the chin gene does not produce ruby cast and often does not create visible shading.  While the shaded gene "bleaches" pheomelanin pigment, weakens eumelanin pigment, and adds a ruby cast to the eyes, the chin gene also "bleaches" pheomelanin pigment, often only has slight effect on eumelanin pigment, and does not add a ruby cast to the eyes.  So chocolate self chins (chocolate "shadeds" with the chin gene) will look even less distinguishable from self chocolates.  You won't see extra ruby cast and you are very unlikely to find shading or any hint of weakened eumelanin pigment.  

What then can you look for?  SOME chin-based animals will show eye marbling which can be subtle gray lines in the brown eyes or brown lines in the gray eyes, or as extreme as a non-dilute appearing to have blue-gray eyes.  So if you have eye color problems without extreme ruby cast, look closely for marbling.  Marbled eyes are a definite indication of the chin gene.  This picture shows extremely heavy eye marbling on a black self chin to the point that she looked black with blue-gray eyes.  

While marbling is a nice way to spot the chin gene, many chin-based rabbits do not have their eye color affected at all.  So you are back to square one - a solid chocolate-looking animal without any clues.  When this happens, you have to rely on genetics to figure out if they are actually self chocolates or not.  This is why it is so helpful to have torts and REWs in your chocolate program, so that if chocolate points pop up, you know there is either chin or shaded.  A chin or shaded-based chocolate point will look the same except shaded-based chocolate points have the pronounced ruby cast to their eyes and chin-based chocolate points MAY have marbling.

Breed chin out the same way you breed shaded out - with REW to bring out the gene and tort (non-extension) to prove it is full color and not hiding anything.  If you just use REW without non-extension, you can end up with chocolate chins that have no obvious chin signs that carry REW, but this does not mean that they are self chocolate.  Non-extension is so important in this situation.    

 What are the genetics of the colors discussed?

Since color names can be confusing as they are sometimes used differently, below are the genotypes of the colors discussed.

Chocolate - aabbC-D-E-
Chocolate Sable - aabbc(chl)-D-E-
Chocolate Seal - aabbc(chl)c(chl)D-E-
Chocolate Self Chin - aabbc(chd)-D-E-

Lilac - aabbC-ddE-
Lilac Sable - aabbc(chl)-ddE-
Lilac Seal - aabbc(chl)c(chl)ddE-
Lilac Self Chin - aabbc(chd)-ddE-
Chocolate Tort - aabbC-D-ee
Chocolate Point (shaded-based) - aabbc(chl)D-ee
Chocolate Point (chin-based) - aabbc(chd)D-ee


As always, please contact me if you have any questions and I am happy to help!

-Barbara

Breeding Blue Eyed White Lionheads – The Vienna Gene

This article was published in the Oct/Nov/Dec 2013 newsletter of the North American Lionhead Rabbit Club, The Mane Musings and updated 4 years late for publishing in the NARLC Guidebook.  Although I wrote it about BEW Lionheads, the genetics of the Vienna gene are the same for any breed of rabbit and so are the breeding principles.  I hope that you enjoy the article and ask that you do not copy any of its content without permission.  Thank you

 

Introduction

Breeding blue-eyed white Lionheads has proven to be quite the journey for me since I started my project with this variety four years ago.  Challenging, but also very rewarding, the BEW variety requires ample patience in addition to a solid understanding of genetics, because of the intricacies of the Vienna gene.  This is an updated version of my article that was published in the Mane Musings in 2013. 

Establishing a Breeding Program and Vienna Genetics

A blue-eyed white breeding program should be treated like a completely different breed from your other Lionhead colors in a sense, because you cannot use animals from your BEW program with other color lines.  Additionally, you do not necessarily want to cross any color into your BEW program either, without careful consideration.  Breeding your BEWs to a colored rabbit should only be done to improve the type/mane/etc. in your BEWs and then all resulting offspring are Viennas and should be treated as such.  Having a Vienna color breeding program will mean that you have many non-showable bunnies popping up, so make sure you have a plan to move them on when needed.  Breeding BEWs is a one-way street.  Other colors can go in, but you cannot take rabbits from your Vienna line and put them in a non-Vienna breeding program.

It is important to understand the terminology used by BEW breeders.

BEW – stands for blue-eyed white.  It is a pure white rabbit with bright blue eyes.

Vienna Gene – Expressed as “V” (regular) or “v” (Vienna).

VM – Stands for Vienna Marked or “Mismark Sport”.  It is when a rabbit carries the Vienna gene and shows it in spots of foreign color in the coat.  This is never showable. 

VC – Stands for Vienna Carrier.  A rabbit that carries the Vienna gene but does not show it.    These are the most important to clearly identify as Viennas to your customers and in pedigrees.  You do not want someone thinking that their Lionhead is just a regular solid colored rabbit and then get the Vienna gene spoiling their color down the road.

The genetics of a BEW are as follows:

----------VV – “regular”, non-Vienna rabbit.  Most Lionheads are VV and do not have the Vienna gene. 

----------vv – blue-eyed white.  It takes two copies of this gene to be a BEW.

----------Vv – Vienna Mismark or Vienna Carrier.  One copy of this gene may or may not show up in the rabbit’s phenotype. 

The Vienna gene is a masking gene like REW.  All the dashes in the genotype are unknown genes that vary by the rabbit.  Like REWs, you can have BEWs that are genetically torts, chestnuts, otters, harlequins, or any variety of colors hiding behind the white.  Many BEWs do hide some of these more unusual colors. 

Gene Expression

How are BEWs the color that they are?  A BEW is white because the Vienna gene wipes out the cells that produce pigment in the fur (melanocytes).  A VM’s spots of white are literally spots that do not have any melanocytes.  The eyes are blue for the same reason; the pigment in the iris of the eye is normal, but the pigment in the stroma has a slightly different type of cell and is missing melanocytes.  The combination of normal and missing pigmentation produces the effect of a blue eye.  The blue is an optical effect – the eye is not actually blue but appears that color much the same way that the sky appears blue, but is not.  Therefore, the blue eyes can seem different shades in different lighting.  True eye color is best evaluated in natural sunlight. 

BEW eye color also changes from kits to mature animals.  When the eyes first open, they look very dark - almost black.  As they mature, the color slowly brightens.  At what age the eye color stops changing varies somewhat by the line, but many do by around 4 months of age. 

 

Working with VMs and VCs

When you breed BEWs, unless you are only crossing BEW to BEW, you will likely be working with VMs and VCs.  The Vienna gene has incomplete dominance, so if a rabbit carries one copy of the gene, the color expression can “turn off” or “turn on” by mere chance.  A VM can be very subtle like a colored rabbit with a speck of blue color in the eye and a white toenail, or it can be more dramatic with a blaze, color on the neck and shoulder, and white feet, for example.  Although the markings are somewhat random, they still tend to follow a pattern of typical depigmentation.  Blazes and nose spots of many different shapes, blue or partially blue eyes, neck and shoulder markings, and white feet tend to be the most commonly seen markings.  Eye color on VMs varies just as the spotting does.  It is often regular colored (brown or blue-gray), but can also be pure blue, or very often partially blue or odd eyed.    

VMs or VCs can be very valuable in a herd.  Many BEW breeders will occasionally bring in a non-Vienna rabbit of compatible color genetics to improve quality and bring in new blood.  It takes at least two generations working this way as the first generation of kits will all be VMs and VCs. Vienna-marked and carriers can be bred to a BEW for BEW offspring or with each other to achieve the same goal.  I do not recommend breeding a VM or a VC to a non-Vienna rabbit because you will not get any BEWs and the number of VMs will be too small to make the cross worth it.  Some of the kits produced will not carry the Vienna gene at all and these cannot be told apart from VCs without test breeding first. 

 

Purple Eye Effect

There are several causes of a purple eye effect in BEWs.  This happens when additional factors contribute red to the eye color and, in combination with the existing blue, can look purple overall. 

A ruby cast is a common cause of purple eyes.  Shaded varieties that have a ruby cast to their eyes like siamese sables, sable points, and smoke pearls will cause this in addition to chocolate varieties such as chocolates, lilacs, and chocolate torts.  Homozygous Vienna genes mask everything, but for some reason do not mask this ruby cast and it will show right through the blue eyes.  The eyes resemble a red eye in a photograph from camera flash - but in real life.  The ruby cast can be described like a translucent red film in the pupil of the eye and it is somewhat reflective.  This effect is sometimes described as purple eyes and it spoils the look of a blue eye considerably.  The recessive nature of these genes make it important to not only stay away from breeding in these animals with ruby cast, but also ones that carry for it.  A black that carries chocolate, for example, can still introduce these genes in your BEW herd. 

BEWs can also have a different purple effect in the eye, not to be confused with the ruby cast effect from chocolate or shaded.  These eyes are blue with visible red/purple veins in them, and are believed to be caused by lack of pigmentation in the iris.  If you look at the brown eyes in some rabbits, you will see that some are very dark and uniform and others are lighter or possibly have somewhat uneven coloration.  This is the same lack of pigmentation being expressed in a more subtle manner in other colors than BEWs.  By selecting away from the latter coloration, the purple veining will disappear and the eyes will be a uniform, brilliant blue.  

 

Other Genes Avoided

There are also several colors that many BEW breeders will avoid, not because they damage BEW color, but because they make color identification much more difficult. 

The first of these colors is REW which is another masking gene.  You can have a rabbit that is genetically blue-eyed white and ruby-eyed white at the same time, but they have ruby eyes because REW will cover patterns in all other loci.  Because of this masking, you do not know if the rabbit genetically is a BEW, a VM, VC, or even non-Vienna depending on the breeding they are out of.  It also makes your chances of getting actual BEWs in a litter slimmer when some of them are double masked with REW. 

The next color that many BEW breeders avoid is broken.  In some crosses, many breeders will depend on retaining VMs rather than non-marked babies so that they know they carry the Vienna gene and broken can mask this very well as it is white on white. 

 

Buyer Education

If you breed BEWs, it is very important to inform all buyers of any BEW, VC, or VM rabbits.  This should be clearly marked in the pedigrees and I tattoo a “V” in the ear of any rabbit from my Vienna line whether it is a BEW or not.  There are terrible stories of entire breeding programs being destroyed because the Vienna gene was lurking behind colors and the breeder was unaware of its presence.  Anyone who raises and breeds rabbits with the Vienna gene needs to understand how damaging it can be if not carefully controlled in its own program.  They also need to ensure that their buyers understand this as well.    

 

Misconceptions with the Vienna gene:

Possibly more so than with other colors, there are many misconceptions with the Vienna gene and BEWs in general. 

·       It is a myth that BEWs are blind, deaf, or have seizures.  This may have been the case early in the development in some breeds due to heavy in-breeding, but it is no longer a problem at all.  I have never heard of this being an issue in the Lionhead breed.

·       Dutch colored rabbits are not caused by the Vienna gene.  Although the blaze and other patterning in a VM may closely resemble Dutch patterning, they are completely unrelated genetically.  VMs are sometimes called “Dutch-Marked” which may lead to further confusion.

·       A white rabbit with blue gray eyes or brown eyes is an ermine or frosty with extremely light color.  Usually you can find these faintly colored hairs on the ears and a BEW would never have them.  A white rabbit with blue gray eyes can easily be mistaken for a BEW. 

·       VMs are not brokens and cannot be shown or bred as such.  Using a VM as a broken in your breeding program will be devastating.  If it is out of Vienna lines, do not cross it with your other colors.

·       Although REWs and BEWs are both white, they are not at all related.

·       REW does not cause a purple eye effect.  REWs that are hiding chocolate can pass chocolate which produces this ruby cast or ones that have the genetics for light eye pigmentation can produce the visible vein effect, but the REW gene itself does not damage color.

·       No other color genes appear to affect  BEW color including dilute and chinchilla.  BEWs with these genes behind them have blue eye color equal to ones that do not. 

 

Conclusion

With striking blue eyes and a pure white coat, BEWs are a stunning variety with increasing popularity and interest. This is not a variety project that should be undertaken without a solid understanding of the genetics behind it.  Careful and responsible breeding of the Vienna gene is essential to a successful and rewarding line of blue-eyed whites.