by Cristina Sherer
After reading quite a few articles on this difficult color and raising this color for a number of years, I've noticed that there appear to be some misconceptions about this color and the genetic structure that produces a nice Red Rex. The first point is that this color is at its very basis an agouti. This is from a genetic standpoint not by just standing back and looking at these animals. It helps to approach every color genetically and break it down into the genetic parts that create the final color.
Before going any further the genetic basis for the color helps us understand it better. Approach every color by breaking it down into parts: pattern, base color, amount of color shown, intensity of that color, where it is placed on the hair shaft and width of rings. The genes in the same order for a Red are as follows: Ax , Bx , Cx , Dx, ee, ww. The "x" means there are several possible genes that could be paired with it. In the same order this means it is an Agouti (dominant), with a black base color (dominant), with full range of color available (dominant,no chinchilla effect),with full intensity of color (dominant,no dilution), black pigment is eliminated from top and bottom rings (recessive,"extension gene"),increased length of middle band and coloring of white areas (recessive). The following table organizes it more clearly:
Ladder of Dominance
**Underlined genes apply to control of Red color**
When one looks at the standard of perfection one gets the impression of a self. The standard stresses a lack of shading and a cream to red belly. In reality, the standard is promoting the hidden modifiers that go into an outstanding Red. The Red starts out as an agouti, much like its cousin the Castor. Basically what you're doing is taking a Castor and genetically eliminating the black from the bottom and top rings in the hair shaft. The strength of the extention genes will affect the amount of smut you see.
But then you wonder about the belly color. First of all, the slate undercolor is eliminated just as it was on the rest of the animal (remember bottom ring elimination). Next, the wide band (ring) gene comes in and puts color into areas that were once white or shaded. Then, those hidden rufus modifiers go to work. Not only do they provide an even darker more intense red, but they also help to color the belly with that same red pigment and darken shaded areas. We can't expect the belly to be as dark as the back since we are starting with an area that was programmed to be lighter to begin with. But, depending on how many modifiers the animal is carrying, the belly can be slightly cream to red. You will find the more intense the back color, the less shading and darker belly color occurs. Isn't this exactly what the standard promotes?
Let's further test this idea. If you breed an agouti to a self your genetic predictions say you will get 100% to 50% agouti offspring depending on the agouti parent's other pattern gene (M,Aa,Aat). Please keep in mind these are predicted percentages. Nature is too random to follow them exactly. I have bred Reds to Blacks and Otters to improve type and have gotten litters full of Castors. This is not the result of breeding self to self.
I wanted to point out further the faint eye circles, inner ear, and under the tail. Are these the hallmarks of a true self? Considering it a self only creates problems when making predictions on litter colors and when trying to decide what colors cross well. I completely agree that breeding Red to Red is the safest and most effective way to increase those valuable rufus modifiers and strong extension genes. But if our type is failing, your otter color needs more red demarcation, your Tn colors need some outcrosses or your castors need that beautiful red hue, shouldn't we conservatively use those color crosses to our advantage?
When you do cross Reds with other colors your best bet is to stay with the full color varieties. This means avoiding any colors involving the chinchilla genes, dilutes, chocolates or whites with no known full color background. A white with beautiful castor parents may work just fine. I stress that whites do not bleach Out color. You can't approach color genetics like mixing paint. An example of a good cross to improve type would be a Castor with a rich red hue. Chances are good it is carrying the rufus modifiers needed and possibly even a red extension gene that would give you a few reds in the litter. Keep in mind that the "red gene" (ee) is recessive and hard to find in other dominant colors that can hide it. When you cross to other dominant colors you tend to end up with a lot of Castors and a few surprises from the hidden recessives. Therefore, you often end up crossing back to your Reds to get Reds in your litters. Smut can sometimes be a problem in part of the litter, but this can be quickly eliminated in future breedings to Reds with good color. I have never found that Reds had to be kept near a window or in the sunniest part of the barn to ensure a lack of smut. I'm sure some breeders believe this due to the sun's bleaching affect, but I find it is a goal best reached naturally.
When your picking out the Reds in your new litter there are a few things to expect. All young Reds have a very distinct shading. They will have a nice rich orange or red back that leads into very prominent light stripes across the sides. Don't panic, this back color will eventually cover the whole rabbit. You can pick out the degree of smut on a rabbit by looking at its ears, nose and lower hindquarters. These areas are going to be the highest concentration of smut and a look at what is yet to come. Keep in mind that all young Reds tend to be ugly ducklings, just like the castors. They are washed out and any degree of smut seems to add to their scruffy look. I have a policy that any rabbit with type and fur will be given a chance unless the smut is obvious all over. I tolerate smut more on the concentrated areas but not over the whole rabbit. About the time you cull (8 to 1 2 weeks) they are old enough to also show you the desired cream to red belly color. One mistake I see often is when a Fawn shows up in a litter and is mistaken for a Lynx. Fawns are Reds that have inherited a dilution gene. The color is diluted out and has a creamy appearance. This is why I stay away from dilute color crosses. Blues are also diluted Blacks. Therefore the smut that is normally black is blue on a fawn. This tricks the breeder into thinking that he or she has that dove gray hue seen in a true Lynx. The best way to know for sure is look at the parents. If they are both Red there is no doubt it is a fawn. The Red can pass on nothing but red genes. That is the beauty of a recessive, they can't hide much. The true Lynx has a diluted chocolate base and is free to express a true Lilac top ring. Reds don't have a top ring! If one parent is not Red, look at their background. See how possible it is that either would give out a chocolate gene. Finally, watch Out for slate blue undercolor. This is not acceptable anywhere and is the strong indicator of a Castor that is trying very hard to be a smutty Red.
Genetics can be a confusing jumble of probabilities and hidden recessives. It is hard to not go into depth when explaining it. Hopefully this gives you a basis for raising one of the harder varieties to raise and gives you an understanding of it's usefulness in other varieties.
2001 National Rex Rabbit Club