The fourth segment of Silver Fox Genetics 101 will cover the A-locus. This one has three possible alleles that have this order in dominance:
- A - agouti
- at - otter or tan patterned
- a - self
Agouti – AA, Aat, or Aa and written as A_ when the second allele is unknown.
It only takes one “A” for a rabbit to be agouti. It looks much like the wild cottontail with a white inside of the ears, eye rings, and undersides of the belly, chin, and tail with colored fur that shows banding on the hair shaft or rings when you blow on it.
Otter or tan patterned – atat or ata and written as at_ when the second allele is unknown.
Self - aa
This has the same coat pattern of the white underside of the agouti, but the colored pattern on the fur is solid without any rings when blown.
This is a solid-colored rabbit all over and a true self can only be “aa.”
Having read these descriptions, have you already guessed that the Silver Fox is a self-based breed? It is. All Silver Foxes should be homozygous on the A-locus with the most recessive allele or “aa.” Because it has the most recessive alleles, we know that it cannot hide any other recessives. When an “aa” rabbit is bred to an “aa” rabbit the only possible outcome is “aa” offspring.
This makes the A-locus on the Silver Fox something we mostly take for granted.
With the four loci we have covered so far, the genotypes would look like this (with unknown second alleles on the loci with dominant alleles):
- Black – aa B_ C_ D_
- Blue – aa B_ C_ dd
- Chocolate – aa bb C_ D_
- Lilac – aa bb C_ dd
- REW – __ __ cc __, but a white Silver Fox should be aa __ cc __
Now a deeper look into when a “solid” is not a “self”:
Although this segment is about the A-locus, we also should understand how one allele in particular on the E-locus can affect the appearance or phenotype by how it works with the A-locus and cause confusion.
As you now know, when a Silver Fox looks solid (except for the silvering that comes in as they age due to another locus), it should be “aa,” but there is another possibility that should not happen although it can so you should be aware of it.
I have had this conversation with at least one breeder that caused me concern about steel and chinchilla, or silver-tipped steel, being experimented with in Silver Fox lines in hopes to improve even silvering appearance. I have suspicions that other Silver Fox breeders either tried it or bought rabbits that carried residuals from this kind experimental breeding possibly decades ago, which is why so many breeders are discovering chinchilla in their lines, as I found in my very first blue Silver Fox doe.
It comes as a surprise when a newly purchased Silver Fox rabbit is bred it to another proven Silver Fox rabbit and the kits have agouti white inner ears or you have one that looks like a self at first but a few days later its fur looks different with varying colors on the hair shaft like gold or silver tips. That is when the breeder discovers that their new solid colored rabbit that looks like a self rabbit is actually a homozygous steel agouti, often called a super steel: A_EsEs.
Steel does not affect silvering nor does silvering affect steel.
A super steel agouti looks exactly like a self, although steel “Es” is a funky gene with modifiers not yet understood, so there could be some hints of steel in some areas on some rabbits maybe, but usually not. This is because one single steel allele pushes out the base color, whether black, blue, chocolate, or lilac, further on the banded hair shaft of the agouti exposing only the tips, making it a gold-tipped steel or, if the chinchilla allele is dominant on the C-locus, a silver-tipped steel.
Steel even does this in the white patterned areas so there is color on the hair shaft that would otherwise be completely white on the agouti. Add the second steel allele on an agouti and the base color typically will be pushed further to cover the tips as well, making the rabbit solid colored and appear to be a self.
On the “at” otter, the colored fur is not banded, so steel is not seen there, but it will affect the white areas the same way as it does on an agouti and an otter super steel will also appear solid like a self.
On the "aa" self, steel is not seen at all because the hair shaft is already fully colored so there is no noticeable effect of the steel pushing the base color out on the hair shaft. Also, it was believed by some breeders that steel will deepen the color of a self rabbit, but this is a myth.
It is quite possible that many Silver Foxes are carrying steel on the E-locus, but it is not really a concern; on true self “aa” rabbits, steel is just not seen. Because of this, steel is something difficult to breed out of the lines and requires cross-breeding with agoutis or otters to reveal it, if that would be a goal. However, again steel of itself is not really a concern because it does not affect the color on the fur of a self at all.
On the other hand, breeding in “A” agouti [or “at” otter] into Silver Fox lines with “Es” steel is a concern. An A_EsEs super steel agouti Silver Fox could be mistaken for a self and would make for lots of disqualified offspring while it would have the appearance of an “aa” self, which is to say it would appear as a Silver Fox is expected to appear.