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What Do You Think?

Observations on Steel Color


by Jill Pfaff

The breeding of steels and the range of colors within the variety has intrigued me for several years. I wrote an article in 2002 describing my observations of the steels at the National shows. Some had obvious agouti traits (like eye circles, crotch markings, and light tails) and there were others that were nearly black with very little ticking.
Our current Standard for steels describes a black body with a uniform disbursement of off-white or cream coloration on some of the hair tips. Undercolor is to be slate blue, carried as deep as possible. Surface color of the under portion of the tail, belly, and legs to be as near the body color as possible. Crotch marks are accepted. Eyes-dark brown. Faults are a lack of steel coloration over the back; brassy or yellow appearance; white hairs in the colored section. Disqualifications include ring pattern over the back and upper sides and white underside of the tail.
This description seems to send a mixed message to me. Yes, we allow agouti traits but not too much. It sounds like ring pattern on the lower haunches is OK. So we are looking for an animal that is in between.
I enjoyed reading the article written by Theresa Kortbein, and thank her for her insights into breeding steel Dutch and now would like to add a few of my own theories and observations. For the last few years I have made a few breeding experiments to better understand the genes involved. Unfortunately, I don't believe it is a straightforward connection between the A series and E series genes and the genetic books available don't even seem to agree.
For those of you that aren't up on the genetics lingo, I'll try to give you a quick introduction. There is a very good article in the Dutch Guidebook by Joanne Parker with really good explanations except for the use of the eg symbols for gray genes which is not found in other books.
Basically, there are 5 genes identified in rabbit coat color. A, B, C, D, E and each has at least two alleles, for example, big B or little b. The most dominant gene is in the capital letters and the recessive or less dominant in small case letters. I like organizing information in tables, so here goes.


Gene Series other alleles
in order
of dominance
Notes/Examples
     
A A, at, a
A=agouti like Grays, at=tan pattern not in Dutch, a=self like black, blue, chocolate, & tort
   
B B, b
BB and Bb not chocolate, bb chocolate
   
C C, chd, chl, ch, c
C=full color in all Dutch, chd=chinchilla, chl=seal, ch=himilayan, cc=albino
   
D D, d
DD and Dd not blue, dd=blue
   
E E, Es, ej, e
E=full extension, in combination with A makes gray, with a seen in black, blue, chocolate
     
   
Es=steel, not fully understood
ej=harlequin brindling
e=non-extension, ee with aa makes torts, with an A (agouti gene) makes orange or gold A-ee

(references: Rabbit Coat Color Genetics by Glenna M. Huffon, Color Genetics of the Netherland Dwarf Rabbit by Bobby Schott)
So there are two copies of each gene one one comes from each parent, so you can figure out what genes an animal has through test mating with animals that we already know genes from their color. Record keeping is an important part of any experiment and making notes on all the colors produced in a litter is very helpful. Another tool I use is Evans Software Program for Rabbit Pedigrees, once you have the animal's colors entered, it will predict genes present.
Now for an example, a blue has self genes aa and the dilute genes dd. When you breed two blues together you should only see blues in the litter, theoretically it is impossible to have black produced from two blues because there are only dilute genes present. This goes for torts also with the non-extension genes ee. Some colors have several genes combinations possible. Luckily in Dutch, it is less complicated than in Netherland Dwarfs. The term Phenotype refers to the color of the animal and Genotype is the actual genes the animal carries.

Recognized Varieties of Dutch Rabbits Phenotypes & Genotypes

Phenotype Black Blue Chocolate Gray Steel Tortoise
Genotypes A-B-D-EE A-B-ddEE A-bbD-EE A-B-D-E- A-B-D-Es- aaB-D-ee
  aaB-D-E- aaB-ddE- a-bb-D-E-   aaB-D-Es-  

Note: dashed lines (-) are a form of shorthand that mean either dominate or recessive genes can be present without listing out each possible combination. The steel genotypes are in italics.

Now, back to the steel color. I don't believe that all black/gray crosses will product true steels. From my breeding experiments some grays (AAEsE) can carry a steel gene but look like typical grays. I tested this theory by using several gray does with steel in the background to a black buck half tort (aaEe). There were outstanding colored steels in some of the litters and I believe that the best-colored steels have both agouti and self genes Aa and one steel gene with another E series gene AaEs-.

gray doe black buck
  aE ae
A Es Aa Es E (steel) Aa Ese (steel)
A E Aa EE (gray) Aa Ee (gray)

At this point I do not see a difference in steels with AaEsE and AaEse or grays with AaEE or AaEe. More litters will have to be looked at to see if there are any consistencies.
Another observation has been eye color problems in steels with eye spots. Sometimes these eye spots go unnoticed through several shows because they tend to be located below the pupil and hidden by the lower eye lid. Several of the steel bucks I have used that have bright steel color have also carried a blue gene. I'm still working on why we use a blue influence but it does seem to work. My theory at this point is that the blue has a co-dominance affect which dilutes the brassiness from the agouti gene. I don't believe there are any true silver tipped steels in Dutch without the addition of the chinchilla gene (chd). All the current steels are gold tipped with the genes ABCDEs and I believe the best colored steels are AaBBCCDdEs-.
To produce silver tipped steels from what I understand the genes needed are ABchdDEs. The only way possible to bring in the chd gene is through crossbreeding from another breed. So far I have heard reports of American Chinchilla, Mini Rex, and Netherland Dwarfs being used to accomplish this silver tipped steel. Another issue is loosing the Dutch markings coming from the dudu genes. All other breeds carry DuDu. So every time you cross to another breed you produce a Dudu gene combination that will not have all Dutch markings in the first generation. There are some other complicating factors I will save for another article.
My hope in writing this article is to generate interest in understanding the color genetics of the Dutch breed to help breeders produce better quality animals and provide a Standard, which is concise and reproducible. I look forward to hearing from other breeder's experiences and discussing color genetics with my fellow Dutch fanciers.

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