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Sabino affecting Roan test?

Itz November 02, 2011 November 02, 2011

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A while ago I hear something about that the Roan zygosity test that’s available today wouldn’t work if the horse was sabino. I haven’t been able to find any info about this anywhere, and even emailed Davis to ask, but haven’t got a reply to my mail. According to what I heard, the sabino would somehow affect the result of the roan test since both ere located on the KIT area. So my question is if anyone here know how that works, if it’s true? And if it is the same thing with minimal “sabino” markings (not SB1, but “normal” markings)? Would these minimal non-SB1 markings make the roan zygosity test ineffective? It was all new info to me, so I’d just like to know more about this subject if anyone in here knows anything about it :)

Daylene Alford Wed, 11/02/2011 - 13:23

I haven't heard anything about this. It sounds to me like this may be a case of things getting confused as they are passed along. For example, someone says that the roan test won't work if the horse is sabino roan, which is correct, but then things got mucked up a bit.

The roan test looks for markers that travel with classic roan. Because of this the test may not be 100% accurate. I would think, the chance of being wrong, would be the same with sabino as with any other gene.

Threnody Wed, 11/02/2011 - 17:46

I agree with admin. It was likely a case of 'telephone' getting information crossed.

Same thing happened with common classic roan being labeled as homozygous lethal when it isn't. Roan is homozygous lethal in guinea pigs and roan in some cow breeds causes infertility in homozygous form. People began applying this information to horse roan as well, hence the misinformation.

I've never heard of SB1 messing with the roan test personally.

Daylene Alford Wed, 11/02/2011 - 18:10

[quote]Same thing happened with common classic roan being labeled as homozygous lethal when it isn't. Roan is homozygous lethal in guinea pigs and roan in some cow breeds causes infertility in homozygous form. People began applying this information to horse roan as well, hence the misinformation.[/quote]

If I'm remembering correctly there was a study done that focused on Belgian roans (which may be a different form of roan) that study did seem to show roan as homozygous embryonic lethal (ie 1/3 of the roan to roan breeding turning up open).

What we now know is that the form of roan that is in QH's and many other breeds is NOT homozygous lethal. To the best of my knowledge, the jury is still out for the drafts.

rabbitsfizz Thu, 11/03/2011 - 03:51

I can certainly attest to low conception rate in Roan to Roan , over the years. We just got into a rhythm of not breeding Roan to roan for this reason.
The whole H/Z lethal thing has only ever been embryonic anyway, and I do think it is still relevant

Itz Thu, 11/03/2011 - 07:10

Ah, I see. Thank you so much for your replies!

But to sum it up, no one here have heard anything about horses with markings messing up the roan test due to changes on KIT that the markings supposedly are caused by?

Threnody Thu, 11/03/2011 - 08:46

Might be referring to markers affecting the test? I know there are issues with Iberian horses and the marker test for dun for this reason.

Itz Fri, 11/04/2011 - 14:25

It might be what the one mentioning it meant, but since I didn't hear it myself I have no idea who the source of the statement is. I tried to email U Davis and find out, but sinnce no one replied to my mail that didn't help me:P

Btw, is there any other lab offering the roan zygosity test, or is it just them?

Daylene Alford Fri, 11/04/2011 - 16:03

The more I think about this the less likely it seems. In order for the roan test to be accurate, the markers they are using have to be "close" to roan. The closer they are the more accurate the test will be, as the chance of any kind of cross over decreases as the distance decreases.

The only way that Sabino could affect the test results is if there has been a cross over were the marker that is usually linked to roan is instead linked to Sabino. While this isn't impossible, it would be linked to a certain Sabino mutation not Sabino in general. So unless the person specifically meant SB1, there is no way to know even if it was sabino that caused the "bad" result.

It still seems to me that the most likely scenario is a miss communication.