B/b Genetics and Chocolate New Zealands

I have been studying rabbit genetics of all things lately.  Mostly because a friend of mine has started to bounce around the idea of creating a new variety of New Zealand (NZ) Rabbit: Chocolate.  Her desire to bring friends and interested people on board for the project got me thinking about genetics and wondering how it all worked; especially if I was going to consider joining her in her chocolate NZ rabbit experiment.  So off I went to study genetics and this is what I learned.

There are ten different genes that help to determine the color of a rabbits fur.  They are A Through E, En, Du, Si, V, and W.  I have to be honest and admit that I am still learning so for now I am going to talk about the one I think I understand B and b.  Rabbits have 22 pairs of Chromosomes and the B gene or chromosome pair decides whether your rabbit has black or chocolate in their fur.

B = gives you a black band in agouti fur and in self colored fur it gives you a solid black color.

b = gives you a brown band in agouti fur and in self colored fur it gives you a solid chocolate color.

Now it gets interesting because we have to talk about which one comes first or is dominant in our chromosome pair.  When you have a BB pair of chromosomes they are the same and are called homozygous because they match and you will have a black furred rabbit who produces black furred offspring.  The B (black) is the dominant gene and when paired with a b (chocolate) gene the black will always win and be the color that shows in the fur.  This is called a heterozygous because they aren't they same and now the rabbit has a chance to produce chocolate offspring because it is a carrier of that recessive or non dominant b gene even though it looks black.  When you have a bb pair of chromosomes there is no dominant gene because they are both recessive and you have a chocolate furred rabbit who can't produce black furred offspring because it doesn't have the dominant gene.

So what does this mean if I want to try and breed chocolate NZ rabbits?

Well I have a couple of options.  I start with a test breeder or two that are chocolate.  I am thinking that I will want to have my test breeder be a chocolate satin because they have the same body type of a NZ and that will make developing this new variety a little easier.  Then I will need to breed my Black NZ bucks to this chocolate satin doe to see if any of the the offspring are chocolate.  Because I know b is recessive this breeding would let me see if any of my bucks carry this recessive gene even though they look black.  And because the black is always dominant I will probably need to test each one a couple of times just to be certain.  I will also need to do the same test breeding with my black NZ does to a chocolate satin buck to see if any of them are carriers of the recessive b gene.  Then if I get very lucky and I find that I have a buck and doe who do I will start breeding them exclusively until the random roll of the gene pool hits on some of their offspring and I get a kit or two that are chocolate because they received the bb pairing, by getting one b from each of their parents.

The next option that I have is to get a chocolate satin doe or two or a buck and breed them into my NZ line using their offspring to then test breed as chocolate carriers and continue as with the first options plan.

With either option, it is going to be a long process and project to get the future offspring to be consistently only bb animals and meet the NZ standard of perfection that is put out by the ARBA.  Not a project for the faint of heart, or even for the type of person who like results quickly and lacks the ability to see the bigger picture.  But the more I think about the more fun I think it would be to try it.  To be able to say I worked on that and I helped to develop a new variety and ultimately maybe improve the breed just a little bit.

If you are interested in learning or more joining the project you can find the group over on Facebook: Chocolate New Zealand Project.