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