@nicalandia
I have Spitzhaubens - the normal silver, gold, and chamois; two blue gene sublines; and white.
But I've got a question I've never found a good answer for regarding the yellowing of the feathers due to the sun (generally most pronounced on rooster feathers).
Observations:
- My white (actually Silver and probably splash spangle - no chance of dominant white) Spitz roosters do not yellow.
- I have traditional Silver roosters that yellow and some that don't (same family line, no Ap (autosomal red) that I've ever observed). <--so not necessarily z-linked unless homozygous recessive...or polygenic?
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- I have (recessive) white Ameraucana hens that do not yellow (have never had any white males), and I always noticed that my lavender Ameraucana roosters would go clear/yellow around the edges of their male feathers. I hatched their offspring due to a predator taking out the lav males, got all females strangely, and the white females have also crossbred with the silver spitzhaubens, no offspring (F1, F2) has ever presented with any pheomelanin. (There are 2 F2 roosters that are pure white with crests, muffs, and beards, and black tail feathers - very cool looking. Also no yellowing.) <--so presence/absence of Ap can't be the whole story, but maybe combined with a weak eumelanin inhibitor?-->
- My female spitzhaubens of any color don't yellow*, but they also stay under shade in pens, they can sunbathe, but they don't get near as much sun as the roosters. <--probably not relevant-->
- My chamois spitz roosters (dominant white) don't yellow, but I wouldn't really expect them to where their white is anyway. <--probably not relevant other than known gold and potential Ap.-->
- In my gold/chamois (ss) males, especially with autosomal red, the Ap is more pronounced in the same areas where the yellowing tends to occur in my silver (SS) birds - saddle and hackle. <--and we know this to be an effect of Ap.-->
- Again, like the lavender Ameraucanas, the SS birds with yellowing looks as though it's a faint lacing pattern on those pointed feathers. My ss roosters with Ap are just uniform on those same feathers, no "lacing". (I don't have any Ss birds that aren't purely from the white/lav Ameraucana or Spitzhauben lines, so they're not considered.)
- No one has any significant differences in their shoulder feathers. <--another known target of Ap-->
- I don't consider any of my ss birds' coloration to be rich enough to be mahogany, so I assume it's not present in my flock.
Do you know what's at play here? Some recessive Z linked gene, Pg, and Ml in combination with a eumelanin inhibitor? Or, is the delivery of pigmentation to the male feathers more independent and related to protein/amino acid regulation? Or, there's a sex-linked, recessive, UV inhibitor-deletion gene yet to be discovered? (<-- trying to work out how that would work, my best stab at wording it.) Or, some z-link related to the absence of Ap, in the presence of pure silver (SS)
and a strong eumelanin inhibitor or restrictor = sunscreen?
Like I said, the only answers I've ever found on this are generally plagiarized from each other and make no sense in their supposed genetic explanation of the issue...or blame it on corn.
*Unless S- with a "gold dusting", they literally look like Ss. I found the reason that happens, but I don't remember it right now. I don't think it was autosomal red, but it was something the silver male wasn't pure for, iirc.
And just as a side note relating back to the bushy eyebrows/long feather rooster. I have hens that I know for certain have no polish in them, and most casual observers would insist I'm lying, but the difference I see versus known polish blood hens is that they tend to be so bushy that you can't see the hens eyes easily. Now that I realize this could be the action of a single gene, I'm going to have to keep better notes. What gene is long feather or where can I find more info on it? (I have the Hutt, Reeder, and Van Dort books, and a few others if it's in one of them.)
I'll try to get some new pictures in my album when it's not freezing rain outside.