Thursday, July 5, 2012

Understanding the c allele gene or The Gene Responsible for the REW Rabbit:

There are specific genes that are responsible for all the colors and combinations you see in the various breeds and varieties of rabbits.  Some people specifically choose breeds based on these factors because it can be a challenging and rewarding process to produce the type of coat they are after for the show table.

The American Chinchilla is a breed that only comes in one recognized coat: chinchilla.  This is the same for the Standard Chinchilla as well as the Giant Chinchilla. 

Examples of normal chinchilla coats:

 

However, when you have two chinchilla looking rabbits give birth to pink or other colored rabbits, it will make you go “Hmmm?” and wonder what the heck is going on.  That was the case when a buck from my herd was bred with a doe of another breeder’s herd.   When the doe gave birth, there were a couple of pink kits.  I then vaguely remembered the breeder I had purchased my buck from saying something about the possibility of a white (aka: REW or Red/Ruby Eyed White) New Zealand being somewhere way back in the lines. I was brand new to the American Chinchilla breed and fairly new to rabbits at that time and it didn’t occur to me what it meant until the pink kits came along…

This:











Plus this:












Equal this?????:












What!?!?!?!?!?

Confused?  I know I was. After consulting with other more knowledgeable breeders on the subject, and after a lot of tense conversations with online American Chinchilla clubs (it is a sore subject and very political at times), I finally found a few people willing to mentor me in order to gain better understanding to just how this gene works. 

Here are several links on rabbit coloring genetics and specifically for American Chinchillas:

http://www.thenaturetrail.com/rabbit-genetics/rabbit-color-genotypes-chart/


http://www.rabbitgeek.com/file/amchincolorgen.pdf


http://www.rabbitgeek.com/file/amchinwideband.pdf


http://www.raising-rabbits.com/rabbit-genetics.html


For the purpose of this treatment I will be focusing exclusively on the little c gene.  The little c is possibly the easiest of all the color genes to understand.  It is recessive.  This means in order to see it expressed, (as in the rabbit is a REW), both of it’s parents had to have it. This comes in handy for identifying who may be a carrier of the recessive gene in your herd, as was the case for myself and my fellow breeder.

If you breed two “normal” looking chinchilla rabbits, and they produce offspring that are REW, then each of those parents are now identified as carriers of the c gene and you should seriously consider removing them from your breeding program if you plan on producing pure bred chinchilla rabbits for sale. 

However, they are very valuable once identified to retain and use as test breeders for the other animals in your herd. It also makes no difference if you are breeding for meat, or even for show.   As long as the rabbits from the litter meet the standard for their breed, then they can still be shown.  It is only an ethical dilemma for those of us who wish to purify the blood lines and produce 100% purebred animals.

What we have done is retain some of the REW rabbits produced and kept them back to test breed with our other rabbits.  I was happy to see that I was able to clear several in my herd.  I still have one buck and one doe to clear.  In fact, one of two uncleared rabbit’s offspring (a doe) that I recently bred to a buck that was brought in from out of state by my friend ended up producing three REW kits in her litter. 

I was able to see that the doe inherited the c gene from at least one of her parents and the out of state buck thus has been identified as a carrier as well.  I suspect my doe’s mother to be the one who passed it on since we earlier were able to identify the grandmother to be a c gene carrier from an earlier test breeding. 

I asked a breeder more knowledgeable than myself to explain the percentages when you breed carriers and non-carriers to give you a better idea of what you can expect.  My additions are in bold. It is explained below:

When you have an REW carrier (c gene), it has 50% REW gene and 50% chin gene. If it is bred to a non-carrier (which would be chin X chin), the offspring will be approximately 75% chin, 25% REW carriers, respectively. Most wouldn't be carriers, but there would be enough to cause issues later.
This is the reason inbreeding to make the gene present itself won't work. The majority just won't be carriers, so you'd have to breed each rabbit with its entire family as a test breeding. I don't think most breeders have that much cage space.

If you breed two carriers, you would get 25% chin, 50% carriers and 25% REWs. (25% will be normal non-carriers, 25% will be REW and carriers, 50% will look normal but be recessive gene carriers that could be passed on later- so 75% of these rabbits now have the gene).

If you breed a REW (expressed) to a c carrier, you would get 50% REWs and 50% REW carriers. Obviously, I wouldn't hold any back because they would all be carriers. (Half would be REW and half would be “normal” looking chinchillas but all would have the c gene).

A non-carrier would produce 100% carriers if bred to an REW, but no REWs, because the "c" gene is recessive and would be hidden by the chin gene. (The kits will all look like “normal” chinchillas since the chinchilla gene is dominant but all will have inherited the recessive gene and could pass it on later).

My advice would be if you end up with a litter with any REWs in it, to cull the entire litter.  However, not all will end up inheriting the c gene if those kits came from two “normal” looking chinchilla rabbits.  But, you would have to plan on holding back any of the kits you thought promising to breeding age (approximately 6 months), then breed them with either a known carrier or a REW rabbit, then wait another 30 days and see what happens.  If you don’t get any REW kits in the litter it is most likely that they are not a carrier themselves and you can in essence clear them.  (Please note that not all percentages work out 100% with each and every litter.  It is only based on odds and is still possible to have a recessive c gene carrier and not get any kits in a litter if it is bred with another chinchilla-looking recessive carrier. If it was bred with a REW rabbit then I would feel 100% satisfied).

Hopefully you have stayed with me this far and it makes sense.  If not, here are the basics you need to understand:

  • If you breed two “normal” chin rabbits and get “normal” looking offspring then each parent either carries the normal color genes or only one is a recessive carrier and you won’t see it expressed by producing any REW kits. You cannot rule out either parent as a carrier this way.

  • Breed two c gene carriers and you have better odds of producing some REW kits and you will then know each rabbit you bred are carriers of the gene.  You won’t know which of the kits inherit the gene unless you grow them out and test breed them. 

  • Breed a “normal” chin rabbit with a REW rabbit (recommended to better identify potential carriers and rule out your breeders definitively) and if they do not produce any REW kits then your normal looking chin is not a carrier.  If they produce any REW kits then it was.  However, since one of the parents had the gene expressed (as in one of the parents is a REW rabbit) 100% of the kits will have inherited the gene and should not be sold to others wanting to start up their own breeding program. They would be valuable to use as test breeders since you know they are carriers themselves.

As a final note, I wanted to explain a bit about the politics of discussing the c gene in the context of any non-REW breed of rabbit.  Especially when it comes to rare breeds, but really with any purebred variety, people don’t like the idea of finding out that their blood-lines may have been tainted sometime in the past or that they may not be a purebred rabbit at all. You have to understand with any rare breed, sometimes people just don’t have another one to breed it to.  Some people may have felt in order to keep their rabbit’s genes going it was better to crossbreed them then to not breed them at all.  The American Chinchilla genes have been kept going since the 1920’s in part because of this type of breeding.

Also, since the American Chinchilla is a commercial breed (ie meat breed), it is of the same body type and class as the New Zealand.  To me it makes sense that the backyard meat raiser may have no other option but to crossbreed if that was all they could do.  Some even think the New Zealand was used in the production of the American Chinchilla breed even though the official history states it was selectively bred for large size directly from Standard Chinchilla stock.

The politics of it comes into play whenever you get a group of mainly meat breeders discussing the topic of the c gene with mainly exhibitors.  The exhibitors may feel it that the gene was introduced into the blood lines by meat breeders who wanted to improve the overall appearance of the chinchilla in terms of body size, grow out rates, etc.  The meat breeders perhaps think it was exhibitors trying to get a better type for the show table.  It may have been some of each or none at all.  I even personally overheard a judge at a show say that one could “improve” their American Chinchillas coat by breeding in a REW New Zealand into their blood lines!

There are even reports of issues with black kits in the Standard Chinchilla populations and “ghosting.”  I won’t go into the genetics of those colors and combinations but know that to have sports or other color kits pop up in your litters it not as uncommon as some people might make it out to be. (A sport is a rabbit in a litter that is not true to it's type or has a different color or coat markings for it's breed/variety).

However the gene got into the bloodlines isn’t important.  Understanding this gene and how it is passed on to the offspring and how to identify it and remove it is.

The recessive c allele that produces ruby eyed white rabbits is nothing to be afraid of.  With a little research and time, you can fairly easily remove this gene from your lines and end up with only chinchilla rabbits. 

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