Castor vs Castor/brown castor/chestnut in Rex

[White's family farm]

Hi all!

I recently got a beautiful Castor doe (we named Ruby, after her red undertone)!


I am absolutely in love with her coat! But it got me thinking about a "surprise" litter between my (black/std) Chinchilla Rex doe and Broken Black Rex buck. The babies were also 'castor' (some broken, obviously) but looked much more wild/brown than my much more reddish Ruby.

I don't have pics of them on hand, but they looked similar to this bun:

Is this just random variation, or something on the basic color genes (AABBCCDDEE)?

Can I breed for just the Reddish hue, like my Ruby, or this Mini Rex example?:
I'd love to have a couple more Castors, but the more brown variety aren't as appealing to me.

I couldn't find an answer here, but if it is here or somewhere else, I apologize and would love the link.


TL;DR What's the genetic difference between a 'reddish' castor and a 'wild' or 'brownish Castor (2 red, 1 brown castor in post)?

Thanks!

 

[Ducklove74]

The Chinchilla gene may have played a role in the lack of red in your Castors. But, these could just be variations based on other factors A,B,C,D,E are just the 5 common color locus there are others. And only test breeding or known lineage can help you narrow down the recessives they could also be carrying.

 

[White's family farm]

I agree, test breeding will eventually get me there. And there's a lot of other color modifier genes.

I was just hoping someone would know the genes I should be looking for, so I could do some more focused research.

From what I've read on reds, it seems there's red modifiers and non extension 'ee' in the ideal red. But non extension makes it a red (not castor). So maybe it is just a matter of having 'red modifiers'?

 

[MuddyFarms]

I have had the same or a similar thing show up in my Rex where I got a wild-looking castor. Not the smooth, even coloring of my castor buck. It looked like it had steel-colored tipping or something on top of a black/brown coat. But then I have had many great castors as well that match the buck. I was suspicious of the steel or chinchilla genes, but I am not very familiar with those genes, yet.
I would like to hear what you find as you research.

 

[SableSteel]

Chinchilla gene has nothing to do with the difference in these castors
The difference is in Rufous modifiers. Castors need selective breeding (for more rufous) to get that nice red color. With chinchillas and blacks, you can't see their rufous, so there is no way to selectively breed for it and they tend to have less rufous modifiers. When you get a castor out of chinchilla & black lines, it will have less rufous modifiers as well and therefore be less red than a castor out of castor lines that have been specifically bred for better color.

 

[MuddyFarms]

Chinchilla gene has nothing to do with the difference in these castors
The difference is in Rufous modifiers. Castors need selective breeding (for more rufous) to get that nice red color. With chinchillas and blacks, you can't see their rufous, so there is no way to selectively breed for it and they tend to have less rufous modifiers. When you get a castor out of chinchilla & black lines, it will have less rufous modifiers as well and therefore be less red than a castor out of castor lines that have been specifically bred for better color.

Awesome- thanks for that explanation! That is something I hadn't been able to research yet, so it was confusing when I got that kit.

 

[White's family farm]

Yea, and that seems to be the consensus; reddish Castor breeds like Red. It's based on the Rufus modifiers, and getting the right amount takes a while (just have to keep the best and brightest consistently. Preferably from other red based buns).

Thanks for the feedback everyone!