... Simplified
When we first got started breeding the kind of rabbits that you pay attention to things like "Color" we were at a total loss. So many varieties and so many fine points about the color. We did not want to make mistakes but we didn't have an inkling of what we were doing. We bred a few "rainbow colored" litters and then found out that each color was not always the best representation of that color. We had both sat in on the few biology classes in high school where we made the little allele squares and figured out how many roan shorthorn cattle we could breed, if we owned shorthorn cattle. That was enough of that stuff for both Mike and I. We don't have interest in figuring out all the alleles on our rabbits. We also find that colors that are in our rabbits' pedigrees generations ago and do not show on the three generation pedigree come back to haunt us. We learn what our rabbits will produce by following some basic color crossing rules and by observing what we find in the nestbox. Then we plan our next breedings accordingly. At least by using some basic rules we don't get too many surprises and not too many rabbits that are bad representatives of their color variety.
One article helped us out immensely. I can not find the article anywhere else on the Net to link and the copy is not the best for scanning, to so I have typed the whole thing out manually for you here. We found this article in the 1996-2000 Rex Club Guidebook. Please keep in mind that all the colors mentioned here are possible to breed in Rex, however, not all of these colors are recognized colors in American Rex.
The article does not address the genetics of the broken variety. I have provided this link for you to read about the genetics of the brokens: Broken Genetics
Please keep in mind that color genetics runs the same for all breeds, provided that the color you are seeing is actually the what it appears to be "genetically".
Color Crossing Rules for Rex Rabbits
By: Richard Rallison
This article presents a clear and meaningful guide as well as presenting genetic reasons for avoiding certain crosses. No personal opinions have been expressed except as noted and no recommendations are made without establishing a genetic basis for that recommendation. Groups are chosen and assembled based on one or two common gene pairings per group. The common genes at the right of the color name.
Based on genotype alone and considering only the five major gene locations, the colors within the following groups are compatible to interbreed.
Group Color names Common Names
1 Castor, Lynx, Opal, Cinnamon C & A
2 Black, Blue, Lilac, Chocolate C & aa
3 Seal, Sable, Siamese aa & ch
4 Chinchilla, Beige A & ch
5 Red, Fawn, Tortoise-shell ee
6 Tri-Color, Harlequin, Magpie eje or ejej
7 All Colors of Marten atat & ch
8 All Colors of Otter atat & C
9 Californian CHCH
10 White cc
Certain of the above groups are also compatible to interbreed without damaging gene interaction. Groups one and two may be interbred with few consequences as may groups three and four. Groups five and six may be interbred because of the incomplete action of the e and ej genes. Groups five and six can be interbred with groups one and two without serious consequences, but not with groups three, four, seven or nine.
Animals that carry the C gene, groups one two, five, six, and eight will breed problems eventually if they carry any gene in the albinism series (C, CH, Cchl, C chm, Cchd) such as Chinchilla or Californan genes. All of these recessive genes work to eliminate red pigment and decrease black pigment production. Castors and all other color banded varieties are selected for rich red band color which means we concentrate modifying genes that produce more red pigment. This is possibly the reason a good colored castor bred to a chinchilla produces washed-out castors and brown-black chinchillas.
Most of the oberved detrimental or beneficial effects reported by breeders who mix colors are the result of transferring color modifying genes and have little to do with the major color genes with the exception of the presense of any single albinism series gene. A brown-black chinchilla could possibly be used to improve your castor or opal by enriching the midband color but the chinchilla gene would eventually pair up in linebreeding and eliminate the color giving back junky brown-black chinchillas or washed out opals which could also be identified as grey or squirrel.
The key to understanding the effects actually observed in color crossing is to recognize the possible presence of one or more modifying genes, not related to the major color genes. It is not safe to assume that breeding black to blue will darken the blue, even though such observations have been made repeatedly in limited experiments. The black gene has no effect on the blue dilution gene; it isn't even present in a blue rabbit. The truth is that any rabbit from groups one, two, five, six, eight or ten could possibly be used to darken the washed out blue. The only requirement is that the black line used has been selected over many generations for the blackest possible black, which would indicate a cencentration of dark melanin production intensifiers in the genotype.
There is no color code to define a genetically pure albino (pink-eyed) rabbit, nor could you attribute any general color cross guidelines for it. Albinos are always colored rabbits in disguise and would be compatible with whatever color the albino genes we masking. Obviously, it could not be chinchilla, californian, seal, sable, beige, siamese, magpie or marten. A genetically pure white rabbit has pigmented eyes (usually blue), no more than one albino gene and is quite rare. The albino gene is believed to cause white toenails or white spots in colored animals. It often masks modifying genes in albino rabbits that can do more damage to colored offspring than the albino gene itself.
There is a strong possibility that any of the albinism genes can contribute to lighter coat color, cause light toenails, and make colors thermolabile (sensitive to local skin temperature). Breeding black to seal may help the seal but is a detriment to the black. If you kept a black from such a breeding and it was used to cross with castor, the result would be the same as breeding a chinchilla to a castor and would be very difficult to clean up in future generations.
There is a tendancy to accept advice from experienced breeders based on their color crossing experiences; but you may find that from herd to herd the stories and advice will sometimes be contradictory and may confuse you. Conclusions based on limited observations within a closed population will not necessarily carry over to another similar but unrelated population, except where major color genes and primary effects of crossing are being observed. The secondary effects--the shading, ticking, spotting, intensity, and other color distributions--may be the result of heterozygously inherited albinism series genes and/or the presence of one or more modifiers, such as the red intensifiers, black intensifiers, wideband gene(w), silver gene (si), or the extension and steel gene (Ed and Es).
The questions each breeder must answer about any cross for improvement are:
1. What is the major goal or reason for making the cross?
2. Can I live with the possible color problems I may be creating?
Many breeders report success using albino stock to improve colored stock and have been successful at identifying, by testing for single albino genes, the carriers of the gene in subsequent generations, thereby completely eliminating albinism problems by the second or third generation. If no albino offspring are present in a litter of eight from a colored doe by an albino buck, then the probability that the doe is free of all the albino gene is 99% or better. In other words, one breeding to an albino is a sufficient test. The offspring, however, are obviously all "c" carriers and should be used as such, probably for meat and skin only.
If the color cross is made for improving type or size in one color and must be done with an incompatible color because of limited resources, then also be aware that virtually all color problems can be observed amd culled, or tested for an culled, so that with some ingenuity, perserverance and amortized expense, the problems you create can be corrected. Breeding within compatible color groups will save time and yield a higher proportion of saleable products.