Test breeding Silver Fox herd

[Zass]

It's just opinion on my part, but I strongly doubt that harlequin ej affects the placement of si silvering. Silvering seems to follow the rules that most white pattern genes follow, where it seems to overlay any coat color, except bew or rew which hide it. White patten genes being things like dutch, vienna, broken, and silvering.

I would agree that silvering is a white pattern. If fact, if it happens to be a KIT gene mutation, like roan in horses, then a rabbit should not be able to be homozygous for both broken and silvering. That could be a truly fascinating breeding study if someone wanted to try it. It could actaully help geneticist locate the mutation. To bad I don't have access to silvered rabbits.

There have been really really rare cases of a horse being homozygous for one KIT gene mutation, and also having another (there are over 20 known KIT gene mutations in horses). However, it requires some interesting genetic crossover stuff to happen.

Wait a minute, (it just finally occurred to me ) since both broken and champagne style silvering behave as visually dominant color patterns, an animal could be heterozygous for both, and both could still show on a coat, right? You just wouldn't be able to get, silvered charlies. I'm not sure if one can visually determine if a rabbit is homozygous or heterozygous for si silvering..

 

[alforddm]

Wait a minute, (it just finally occurred to me ) since both broken and champagne style silvering behave as visually dominant color patterns, an animal could be heterozygous for both, and both could still show on a coat, right? You just wouldn't be able to get, silvered charlies. I'm not sure if one can visually determine if a rabbit is homozygous or heterozygous for si silvering..

Yes, this is correct. Ideally, you would breed a true charlie to a rabbit that is homozygous for silver and get broken with silvering. Then breed these back together. If the mutations are on the same locus, you should get only rabbits that are homozygous for silver, homozygous for broken, or heterozygous for both. You would probably have to test breed some of these to make sure they were actually all charlies, homozygous silver, or heterozygous for both.

If the mutations were on different loci then you would get a much more diversity. Including rabbits that are homozygous for both or have neither.

 

[Zass]

Darn, for some reason i thought I'd be able to use any of the broken mutts I see posted cheaply. :lol: I'll have to be on the lookout for a genetic charlie...

 

[alforddm]

Just by two cheap broken and breed them together to get your charlie. :lol: Great excuse for more rabbits right?

 

[twr]

Vienna hasn't been located for sure, but due to the blue eyes it probably isn't a KIT gene. Due to the way KIT functions, KIT gene mutations usually leave the eyes brown even if the rest of the animal is white. Stranger things have happened but at this point I think it's "probably" not a KIT gene mutation.

I think we can be more sure than just "probably". By my calculations based on how near En is to KIT according to [1] and how far V is from En according to [2], the probability that V is KIT is (significantly) less than 1 in a million. I'm happy to show my working if anyone really cares but I think it would be best to put it in another thread (lots of statistical maths).

[1] Fontanesi, L. et al. (2014) — The KIT Gene Is Associated with the English Spotting Coat Color Locus and Congenital Megacolon in Checkered Giant Rabbits (Oryctolagus cuniculus)
[2] Robinson, R. (1956) — A review of independent and linked segregation in the rabbit

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In case anyone is interested my suggested scheme (EDIT - this has some flaws, see below) for looking for linkage between Si and En is:
Silver x Broken Black
Gives a mixture of black solid and brokens, both possibly silvered (but we don't care at this point).
Take twice as many brokens as solids from the generation above (best to make the selection before any silvering would show up) and cross back to silver.
Ignore any brokens in this final generation. You should have two roughly equal populations of solids, one population with a broken parent and one with two solid parents. Score the two populations for silvering. If the two populations are significantly different then there is linkage between silvering and En and it is possible that there is a KIT allele that contributes to silvering.

This scheme is complicated but it avoids some potentially confounding factors such as En acting as a modifier on silver (only solids are assessed for silvering) and the unknowns regarding exactly how silver work (the two populations being compared are both exactly the same distance from silver ancestors).

EDIT - On second thought the version above will miss KIT-related silvering if it behaves as a simple dominant and can be tweaked to work better with small populations. One alternative is:
Silver x Broken Black as before.
In addition to selecting twice as many brokens as solids, also select a solid to breed them to. Ideally, use one solid buck across all these breedings. When selecting brokens choose ones that are representative of the degree of silvering across all the brokens in this generation, and similarly select solids that are representative of the solids.
The second round of breedings is now F1 solid to F1 solid and 2x F1 broken to F1 solid.
Then assess as before. For both the original and this revised scheme, if there is a silvering allele in the KIT gene, then the solids with a broken parent should have more silvering than those with two solid parents.

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According to [3] below, silvering in champagne d’Argent initially affects only the secondary guard hairs, which had me wondering if silvering in silver fox initially affects only the primary guard hairs (I might even have read that somewhere, but if so, I can't find the reference any more). If so, that would account for the lesser degree of silvering.

[3] Quevedo, W.C. & Chase, H.B. (1957) — Histological observations on the silvering process in the champagne d’Argent rabbit

 

[Zass]

I was a little confused by the write up, Twr. I might be a little extra dense because it's early (for me.)

if there is a silvering allele in the KIT gene, then the solids with a broken parent should have more silvering than those with two solid parents.

Could you explain this bit a little more in depth?

 

[twr]

Could you explain this bit a little more in depth?

Of course. The short version is that if there is linkage between En spotting and silver (or they are alleles of the same gene) then ignoring the spotted offspring in the final generation also preferentially ignores rabbits with "not silvering" genes.

If there is a silvering allele at KIT then there are 3 alleles at what I'll call the k locus just for the sake of this explanation:
ken = english spotting
ksi = the silvering allele
k+ = wild type

In combination:
ken,ken = Normal charlie, equivalent to En,En
ken,ksi = Assume obviously spotted, unsafe to assume degree of silvering
ken,k+ = Normal spotted, equivalent to En,en
ksi,ksi = Silvered
ksi,k+ = Solid, unsafe to assume degree of silvering
k+,k+ = Normal solid, not silvered

1st gen pairing -> offspring
ken,k+ x ksi,ksi = ken,ksi ksi,k+

2nd gen pairings -> offspring
ken,ksi x ksi,k+ = ken,ksi ken,k+ ksi,ksi ksi,k+
ksi,k+ x ksi,k+ = ksi,ksi 2ksi,k+ k+,k+

When we ignore the brokens (as indicated by strikethrough above):
First line (solids with a broken parent) is 50%ksi,ksi (silver) and 0% k+,k+ (not silver)
Second line (those with two solid parents) is only 25%ksi,ksi (silver) and 25% k+,k+ (not silver)

This difference should be visible whatever ksi,k+ looks like. If there are other silvering genes present then there will be additional silvering variation in the 2nd gen offspring, but this variation will be the same in the two populations (provided you take care to avoid bias in the selection of rabbits carried forward to the 2nd gen pairings), so a difference should still be visible.

Similar arguments work if the original silvers are ksi,k+ or if si and en are linked (physically close on the same chromosome) rather than alleles of the same gene.

But if all silvering is independent of spotting then both populations of 2nd gen offspring will be:
25%silver,silver 50%silver,not_silver 25%not_silver,not_silver

I'm using silver/not_silver for the silver alleles to avoid the question of whether silver is dominant.

Hope that makes more sense.

EDIT: Added a short version and fixed some k -> k+
EDIT: Tweaked intro to clarify "a link" -> "linkage or alleles of same gene"

 

[LPH_NY]

The other extension related genes, Es, E, and e also do not affect any of the white patten genes.

Does this mean, that in theory, a kit could be silvered while also displaying Steel? Anyone have/had a Steeled and Silvered kit before?

I just looked at a litter of 6 week old Half Champagne kits this weekend. They were only just beginning to get some silvering, starting on their feet and bellies.

 

[Zass]

The other extension related genes, Es, E, and e also do not affect any of the white patten genes.

Does this mean, that in theory, a kit could be silvered while also displaying Steel? Anyone have/had a Steeled and Silvered kit before?

I just looked at a litter of 6 week old Half Champagne kits this weekend. They were only just beginning to get some silvering, starting on their feet and bellies.

Absolutely. I've had silvered steels before.

 

[LPH_NY]

The other extension related genes, Es, E, and e also do not affect any of the white patten genes.

Does this mean, that in theory, a kit could be silvered while also displaying Steel? Anyone have/had a Steeled and Silvered kit before?

I just looked at a litter of 6 week old Half Champagne kits this weekend. They were only just beginning to get some silvering, starting on their feet and bellies.

Absolutely. I've had silvered steels before.

I don't suppose you have pictures?

 

[Zass]

Absolutely. I've had silvered steels before.

I don't suppose you have pictures?

Not particularly good ones, unfortunately.

With a little imagination, you can kind of see some silvering coming in patches on this little GTS. (Out of a silverfox dam )

This was before I started investing in better cameras. I swear, on close inspection, his coat did display both genes. I had not yet learned how to take coat pics to show things like how steel looks when you blow into it, VS silver... On top of that, he was young, and nowhere near fully silvered out.

What you are looking for in regards to silver tip steel VS silvering is mainly color and location.
A silver tipped steel will be tipped a color that actually looks a little like silver, whereas, si "silvered" hairs are actually white. The white color tends to travel further down the hair shaft than color on steel too.

__________ Sun Jul 03, 2016 6:06 am __________

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[LPH_NY]

Zass, Your photos just reminded me how much I love steels. I think I can see the silvery shimmer on the very bottom right photo. Pictures never do fur justice.