Yes they are separate, they are different, just often get lumped together because they can cause similar markings.
As a color breeder I am surprised you do not have more testing done on your horses to know what they carry and what they do not. I too would test any horse for OWLS that has an off chance of carrying it because you never want to find out the hard way. Just because it has never happened doesn’t mean it can’t if the genes are there. It is a 50/50 shot every time, and the thing about a lot of the color patterns is they can be so minimal that you would never know or you would assume the tiny amount of white are just “Regular” markings.
Sabino and dominant white are different mutations of the same gene. That KIT gene we were talking about earlier. I think you are thinking of Sabino as a certain type of color pattern, the jagged, sort of roany non-tobiano pinto style color pattern. Sabino does cause that color pattern, but Dominant White causes a similar color pattern. They are two different mutations however.
[QUOTE=crosscreeksh;7685727]
So DW is not associated with sabino to make “color”?? They are separate?? Now I’m lost!![/QUOTE]
Correct.they are marked / look alike. In earlier years were thought to be the same but later proved that to my knowledge there is no sabino in Thoroughbreds. In other breeds there is. Tbs is usually expression of DW, occasionally splash or frame. I actually think my stallion is DW and splash , as his dam looks splash… He and his sister have blue eyes.
[QUOTE=crosscreeksh;7685503]
All foals conceived were accounted for. No empty mares, aborted fetuses or OLW foals.[/QUOTE]
If you’re using Puchi-line mares, where there is no LWO, then you wouldn’t have lethal foals. But you really do need to test Challenged, since he comes from a pedigree that possibly carries Frame. If someone knows for a fact that neither Unbridled’s Song (the direct source of potential LWO via Caro) nor his dam are carriers, then you don’t have to worry/test. But I guarantee US was never tested, never will be, and since Frame can be extremely minimal/hidden, even for generations, I would not simply use US’s offspring as proof that he doesn’t carry it.
I think it just depends. TCF’s Puchi Trap produced quite a few at least modestly marked offspring, and I wish I could remember the name of the other mare who seems to reliably pass loud markings. Your observation might (??) lend some credence to this being sex-linked. Maybe? I haven’t heard that mentioned before this thread, so I don’t know if it’s even been considered to be ruled in/out
The genetics here aren’t recessive. None of the Overo genetics are recessive. But unlike Tobiano, they don’t have to appear visually, or might appear only as “normal” markings, including just a star and maybe a low sock.
This does mean they can “hide”, in the context of being loud, because there are more factors than just there or not which play into the phenotype. It has also been shown that sometimes combining 2 DW types, when you don’t even know either parent carries even 1, can produce a very loud foal - check back at the chart I listed earlier. It’s like Splash - can be very minimal in both parents as a heterozygous state, or 1 copy each of 2 different DWs - and when they combine just right, produce something loud.
It’s actually possible that the Sabino1 we know of now is simply just another DW, or that the DWs we know are all Sabinos, however you want to look at it. They were named Sabino and DW because of different phenotypes, but we know now that the SB1SB1 horse (95%+ white) is visually the same as a W5/W20 horse (all/nearly all white), so… I don’t know if “they” will continue to keep sabino and dw separated in perpetuity, or if there will be something to come along such that it makes more sense to call them all “white”
There’s no Sabino1 in TBs 
See above for sabino vs dw.
As for the Splash - there are DWs who present very much like Splash now. Check out the W20/W20 horse in the collage
http://www.tawnyhorse.com/?gallery=dominant-white
There are also blue eyed horses who aren’t SW1, 2, or 3. Is there another Splash? Is it really DW that’s causing those blue eyes? We don’t know yet 
Some even feel Frame can cause blue eyes.
Re blue eyes: I know we don’t have frame… Horses were tested for it .
I feel your confusion! Equine colour genetics can be a messy thing to get to grips with.
DW and sabino are not associated - one does not need the other to make white markings.
Not so long ago DW horses were thought to be sabinos, the really white ones were thought to be the result of homozygous sabino. Homozygous and loud sabino can look similar to DW but it has since been found thatthe DW and sabino patterning are the result of two totally different genes.
Some still remain in the dark ages and refer erroneously to DWs as sabinos. So I can see where your confusion comes from!
Oops I see some others have posted better answers than mine…
Okay…now I am totally confused!! Years ago we bred a Clyde/Irish Draught to Rambo. She had the typical Clyde markings. She had several foals. One pure white, others assorted bays - not much chrome. We bred a what seemed to be dark brown (we called her “chocolate black”) daughter of hers by another stallion (dark brown/no white) to Rambo = 1 bay/star, 2 pure whites/chestnut medicine hats that faded, 1 bright bay/blaze/4 stockings with black ermine around each entire coronet band. Bred her to a black/white tobiano stallion and a bay/white tobiano stallion and got four “truly” black/whites. The Clyde influence produced the markings on some, but how do you know without testing where the pure whites came from…max sabino or DW?? I am more mind boggled after all these explanations than I was to start with!!
Since Rambo was a TB, and couldn’t have had SB1, and it’s the SB1SB1 horses who are all white, then it couldn’t have been the maximally expressed Sabino.
It was DW which produced the all whites, and that makes absolutely perfect sense, given he was W5, and it’s known that W5/W20 easily produces all white horses. Clydesdales are known to carry W20.
[QUOTE=JB;7686648]
Since Rambo was a TB, and couldn’t have had SB1, and it’s the SB1SB1 horses who are all white, then it couldn’t have been the maximally expressed Sabino.
It was DW which produced the all whites, and that makes absolutely perfect sense, given he was W5, and it’s known that W5/W20 easily produces all white horses. Clydesdales are known to carry W20.[/QUOTE]
Thanks…THAT was a perfectly clear explanation!! It seems we were just very lucky with Rambo’s production!! I guess we have a hodge-podge of genes at our farm!!! It was the white daughter that produced the flashy chestnut/chrome filly this year.
