Rex Color Genetics Questions From a Not-So-Newbie

[MamaSheepdog]

I didn't want to hijack Frabo's thread "Rex Colours for a New Person in the Breed" post128112.html#p128112 , but it has me wondering if my Rex barn is all messed up. :?

I purchased my starter herd from a longtime breeder and judge, and left the color choices up to her. She started me with a broken black doe, an opal doe, a black buck, and a broken blue buck, which died before adding his genetics to the gene pool.

So, all of my rabbits are descended from those three animals- black, broken black, and opal.

I have black, blue, opal, castor, and REW. I recently added a pair of lilacs from OneAcreFarm. I have brokens in all varieties listed except the lilac. I have only used one REW in my breeding- a doe- and she was recently culled.

My limited understanding is that blue is the dilute of black, lilac is the dilute of chocolate, and opal is the dilute of castor. :thinking:

So... isn't blue to black a good choice? Castor to opal? Chocolate (which I don't have yet) to lilac?

Currently my bucks are black, blue, broken castor, broken opal, and lilac.

What are my color crossing options?

Otter works fine with any self (black, blue, choc, lilac)

I like the idea of adding black otter to my program, and know that the breeder has that color in her barn. Hopefully I will be able to arrange a purchase.

 

[Bad Habit]

Well, you breed for show and meat, right? I don't think there's any wrong colour combination when what's not suitable for the show table is suitable for the dinner table!

 

[MamaSheepdog]

So far I have been focusing on good type and good eating!

 

[Whipple]

This is for mini rex but it applies to Rex as well. http://mr-colors.tripod.com/

 

[Dood]

.blue is the dilute of black, lilac is the dilute of chocolate, and opal is the dilute of castor

Not quite.

Blue ((aa & B_ & dd) is the dilute of black (aa & B_ & D_) on the D-locus
Chocolate (aa & bb & D_) is also a dilute of black (aa & B_ & D_) but on the B-locus
Lilac is both dilutions (aa & bb & dd) in a black (aa & B_ & D_)

Castor is called agouti or chestnut in non Rex ( A_ & B_ & D_)
Opal is called blue agouti (A_ & B_ & dd) and is a blue dilution of castor

Don't mix blacks with agoutis, other than that you should do fine.

Crossing black to blue should work as long as the blue doesn't pick up any recessives.

The problem of mixing too many recessives is that carrying a recessive often does have a subtle effect on the richness of the desired colour, so a chocolate that also carries blue my be a light chocolate rather than a rich dark one. A blue that carries chocolate may be more sooty looking while one that carries REW will be a clear/clean blue and win on the table.

 

[OneAcreFarm]

Not quite.
Blue ((aa & B_ & dd) is the dilute of black (aa & B_ & D_)
Chocolate (aa & bb & D_) is also a dilute of black (aa & B_ & D_)
Lilac is both dilutions (aa & bb & dd) in a black (aa & B_ & D_)

Where does this information come from, Dood? I have never heard this before. My understanding is that Blue is the dilute of Black and Lilac is the dilute of Chocolate.

Black = B_ & D_
Blue = B_ & dd (dilute)

Chocolate = bb & D_
Lilac = bb & dd (dilute)

 

[Dood]

We are saying the same thing but in different ways

All selfs lack agouti and are 'aa'. Black (aa, B_, C _, D_, E_) is the least recessive of the selfs.

Lilac is a diluted (dd) chocolate but where did the chocolate come from?

It is on the B -locus and lightens/dilutes the black giving us chocolate ( aa, bb, D_), if a chocolate rabbit also has two blue dilution (the 'true' dilution gene dd) then it will be lilac, but black and/or blue rabbits can have lilacs if both parents carry a chocolate (b) and blue (d) gene.

 

[OneAcreFarm]

I am going to have to respectfully disagree. I have never heard anyone explain it that way. Here is my understanding.

"B" locus is for the Base color
B = black
b = chocolate

These are two separate base colors.

"D" locus is for the amount of total pigment in hair shaft
D = full color (ex. Black)
d = color is diluted out (ex. Blue)

This is where it tells if the color is full or dilute, not the B locus.

 

[caroline]

I am going to have to respectfully disagree. I have never heard anyone explain it that way. Here is my understanding.

"B" locus is for the Base color
B = black
b = chocolate

These are two separate base colors.

"D" locus is for the amount of total pigment in hair shaft
D = full color (ex. Black)
d = color is diluted out (ex. Blue)

This is where it tells if the color is full or dilute, not the B locus.

I agree with this. [D]ense or [d]ilute are determined on the D locus and are separate from lack or rown.

The problems with breeding one color to another seems to show up more in the agouti kits: castor, opal, amber, lynx. I understand that this may be due to modifier genes, rufus for example. If you have a nicely colored Castor Rex and you breed it to a black or blue animal that isn't dependent upon those rufus modifiers then the resulting kits may lack the intensity of color that the castor parent had since the other parent didn't carry them. The self colored rabbits don't seem to have as much trouble with that because they don't have "ring color" to worry about.

It's my opinion that you need to try different breedings in your herd and see what results. Keep good records and select what you like.

In Rex I have heard that the more dilute animals, blue and lilac for example, have less dense fur. Since the fur counts for so much on the score card this may be an issue but you should test it out in your own herd and see what you find.

I don't have time right now to write more, but this is a topic that I find endlessly fascinating and will get back to it when I have more time.

 

[OneAcreFarm]

In Rex I have heard that the more dilute animals, blue and lilac for example, have less dense fur. Since the fur counts for so much on the score card this may be an issue but you should test it out in your own herd and see what you find.

I don't have time right now to write more, but this is a topic that I find endlessly fascinating and will get back to it when I have more time.

Interesting...I will have to start comparing, since I have both Black and Blue, Chocolate and Lilac in my Rex herd.

 

[Devon's Mom Lauren]

Yes, there are TWO colours in the rabbit world... Black and Brown. Brown is recessive to black not the dilute of black, big difference!

The rabbits you have MSD are all compatible..and yes agoutis may not benefit from a self to agouti mating if the self (or even the agouti) lack rufous or ring colour or definition of rings.However if the selfs have (nice) agouti in their background then this may not be the case. That is something that is family-line oriented and you need to be the judge on that one lol. Adding otter is an excellent idea for your selfs but not your agoutis. Otters are awesome!

 

[Dood]

I come from the perspective of the genetics of all species. The choice of chocolate/brown as the 'other colour' in rabbits was actually quite an arbitrary one.

In horses the 'other' colour is the recessive form of the E-locus
In mice and most rodents it is on the P-locus

So I list all the known (or most common) loci mutations in alphabetical order and agouti/self is first.

I used the word dilution because I could not think of a more appropriate term although I realize it may cause some confusion...

This gene, when in the homozygous recessive form, has a lightening effect on eumelanin (black-based colors)only.  It has no effect on phaeomelanin (red-based colors).When brown (b/b) is expressed, it means that the final step in eumelanin production has not been completed and the pigment remains brown.

...I will try and use the term 'lightening' instead.

I really am saying the same thing, but just in a different way.

 

[skysthelimit]

We use otters all of the time with the agoutis. It's great for the otter, increases their rufus modifiers. All of my agoutis are sired by an otter, and all carry black. However, it tends to make for very dark castors. Makes for bad agoutis, but later down the line I can breed back and all of these animals will be able to contribute rufus to future agouti breedings.

What I am trying to do is stack the deck, so I need the minimum amount of rabbits to make the maximum amount of colors. Agoutis are very useful for that. My Castors carry otter or black, chocolate and dilute, the REWs carry otter and black, the otters dilute and chocolate. No non extension gene in the herd. Chins really mess it up, because they can really only be bred to themselves (not really but it makes strange colors). I can't breed them to REW because mine carry otter (I would get martins) or dilute (blue chins). Can't breed them to my blacks because they carry chocolate and dilute. And the Seal and Cal throw a monkey in the works, only because the whole barn carries dilute, so I can breed them to my REW and otters, but at some point I will get a dilution and have something unshowable.

 

[OneAcreFarm]

I come from the perspective of the genetics of all species. The choice of chocolate/brown as the 'other colour' in rabbits was actually quite an arbitrary one.

In horses the 'other' colour is the recessive form of the E-locus
In mice and most rodents it is on the P-locus

So I list all the known (or most common) loci mutations in alphabetical order and agouti/self is first.

I used the word dilution because I could not think of a more appropriate term although I realize it may cause some confusion...

This gene, when in the homozygous recessive form, has a lightening effect on eumelanin (black-based colors)only.  It has no effect on phaeomelanin (red-based colors).When brown (b/b) is expressed, it means that the final step in eumelanin production has not been completed and the pigment remains brown.

...I will try and use the term 'lightening' instead.

I really am saying the same thing, but just in a different way.

I think we can all agree that brown is lighter than black, but in this case, brown isn't just a lighter form of black...it is it's own color and has it's own dilute. It is RECESSIVE to Black, though. Looks like we may have to agree to disagree on this one...