A conversation about "slow graying" and "fast graying" horses

[Haven_tJumpedInALongTime]

I was reading an article about DNA and gray horses. The “slow graying” G2 allele (which has two copies of the duplication gene variant) was found to not have an elevated risk of developing melanomas, while the “fast graying” horse was more likely to develop melanoma. It also said that a slow graying horse usually doesn’t show signs of gray until they are 5-7 years old. It also mentioned that the duplication or tripling of a small DNA sequence in gray horses determines how quickly a horse grays out. Just curious what experiences others have had regarding real life experiences with gray horses with melanomas in regards to slow-graying or fast-graying.

If interested, the article was in the Journal (AQHA publication) page 150 of the Jan-Feb 2025 edition called Gray Matters. Sorry, I can’t find a link to it!

[Simkie]

My mare was quite slow to grey and was euthanized at 13 due to melanoma.

While this research is very cool, and I’m so excited to see work being done, slow greying is no guarantee of no or little melanoma risk.

[poltroon]

This research is so interesting. It is important to see it as a tendency of populations and that individual exceptions will be prevalent. Grey is such a pretty and interesting color and it would be amazing to be able to eliminate the associated risk of melanoma if that’s possible, not to mention what this work will teach us about cancers in general.

I had an early graying horse with melanomas who lived to age 37. I had to euthanize him after he’d been running around in the pasture and managed a hairline fracture of his leg.

[Kyrabee]

My mare was fast graying. She turns 23 this year and has a small-moderate melanoma burden on her tail. One small one on her vulva and otherwise confined to her tail.

She had a melanoma on her when I bought her (we all—vet, owner, me—missed it). You had to crank her tail up over her head to see it. Not something you usually worry about on a long yearling. Frankly, if I had seen it, I would have passed on buying her. That one was removed in the fall of her 2yo year and she didn’t have any more appear until early teens. They are more numerous now…maybe 20 that most are pencil eraser sized. 2 are bigger (robin egg sized) but thus far not interfering with anything.

[Bluey]

We had an Andalusian colt that at four was that mousy all over, no dapples medium to light grey and had to be euthanized due to fast growing massive anal melanomas.
That may have been a rare case, not mean anything as far as how other such colored horses may fare.

[Lusoluv]

My Lusitano was very slow to gray, still had dapples and dark knees/hocks at 14y. Now 25y and no melanomas.

My Andalusian was also slow to gray, tho faster than the one above. Started graying at 9. Last I heard he had no melanomas at 20 years.

[Janet]

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[Xanthoria]

@Haven_tJumpedInALongTime

It also said that a slow graying horse usually doesn’t show signs of gray until they are 5-7 years old.

Meaning they are the previous base color and only start showing gray of any shade at 5-7? That feels unusual. Or do they mean “they go completely white” at 5-7? Neither of those sound right to me. IMEX a fast graying horse is pale gray with maybe dark points by 3-4 and a slow graying one still has dark legs, dapples and mane/tail if that’s how they’re marked at 8-10

[Haven_tJumpedInALongTime]

They are referencing a Nature Communications published article. I believe this is it?
https://www.nature.com/articles/s41467-024-51898-2

[Xanthoria]

That article says “… the variation in the speed of greying is pronounced in certain breeds such as Connemara ponies. In this breed two distinct types of greying are noted, fast greying and slow greying (Fig. 1). Fast greying horses are usually completely white at about 10 years of age whereas the slow greying horses never become completely white but show a beautiful dappled grey color at older ages.”

But that doesn’t match the quote above about 5-7 years… ?

[Haven_tJumpedInALongTime]

Here’s what the Journal article says (I WISH I could find a link!):

“Some horses, the ones that will eventually become white, begin to grow gray eyelashes and hairs at the base of the tail within the first week after birth”, Dr. Andersson says. “A horse that is slow graying will typically not show signs of gray until it is 5 to 7 years old”.

Here is a picture I took of the Journal article:

[endlessclimb]

Even if they knew what were the markers, people would still breed the ones that have melanoma issues. See: HYPP.

[Xanthoria]

Thanks!

[Janet]

@Haven_tJumpedInALongTime

I was reading an article about DNA and gray horses. The “slow graying” G2 allele (which has two copies of the duplication gene variant) was found to not have an elevated risk of developing melanomas, while the “fast graying” horse was more likely to develop melanoma. It also said that a slow graying horse usually doesn’t show signs of gray until they are 5-7 years old. It also mentioned that the duplication or tripling of a small DNA sequence in gray horses determines how quickly a horse grays out. Just curious what experiences others have had regarding real life experiences with gray horses with melanomas in regards to slow-graying or fast-graying.

Sample of size 2. I have two gray Conn x TB halfbreds.

One was quite a dark gray when I bought her at age 5. No indication of her “base color” (bay), but her white sock and blaze were visible on contrast to the gray (coat color, not just skin color) - so “slow graying”. She later developed melanomas (anus, vulva, lips), but they never cuased her any problems. She is now retired (forother reasons) at 28.

The other was a lighter gray at age 2 than the first was at age 5 (fast graying). She is now 14, and never developed any melanomas. (If they are going to develop melanomas, it is almost always before 11).

So my sample is the opposite of your article.

[Janet]

@endlessclimb

Even if they knew what were the markers, people would still breed the ones that have melanoma issues. See: HYPP.

I think that is a rather different situation. As a side efect to its bad features, the HYPP gene (whether single or double) ALSO produced features that were highly desirable. That is not true with the melanoma genetics.

Furthermore, the ACPS (American Connemara Pony Society) has already shown itself to be responsible in dealing with a genetically identifyable defect, Hoof Wall Separation Syndrome.

I can assure you (I am on the Board of Governors) that the ACPS is anxiously waiting for a genetic test to identify the horses most likely to develop melanomas, so they can breed accordingly.

[Posting_Trot]

I didn’t know that about melanomas, that if they’re going to develop them, it’s usually before age 11.

I’m interested because I have a gray mare now (an Irish Draught), and she is turning 16 this year. As far as I can tell, no melanomas (I hope I’m not jinxing myself). Do I get to breathe a great big sigh of relief?

[Texarkana]

@Janet

I think that is a rather different situation. As a side efect to its bad features, the HYPP gene (whether single or double) ALSO produced features that were highly desirable. That is not true with the melanoma genetics.

I don’t know, the color “white” is pretty desirable. Not necessarily a competitive advantage like the HYPP phenotype, but gray horses generally sell for more than their non-gray counterparts in an open market.

[Janet]

@Posting_Trot

I didn’t know that about melanomas, that if they’re going to develop them, it’s usually before age 11.

I’m interested because I have a gray mare now (an Irish Draught), and she is turning 16 this year. As far as I can tell, no melanomas (I hope I’m not jinxing myself). Do I get to breathe a great big sigh of relief?

I think so.
When UC Davis was soliciting (hair and blood) samples from purebred Connemaras (for their melanoma/gray studies), they wanted them from 3 groups.

• Grays that developed melanomas before the age of 5 (or maybe 6, I think they changed it part way through the study)(relatively unusual)
• Grays that developed melanomas between 5 (or 6) and 11 (more of those)
• Grays over 11 that had not developed melanomas.
  (I say “was”, but is my understanding that they are still soliciting more samples, especially from the first (early melanomas) and third (no melanomas) group.)

Unfortunatelly neither of mine are purebreds, so I could not give them samples.
The reason for wanting only purebreds was to make the REST of the genotype (anything not related to gray-color and/or melanomas) as similar as possible, The Connmaras, being a relatively rare breed, are somewhat “inbred” in comparison to the overall horse population.

[Janet]

@Texarkana

I don’t know, the color “white” is pretty desirable. Not necessarily a competitive advantage like the HYPP phenotype, but gray horses generally sell for more than their non-gray counterparts in an open market.

That is not my experience. I know far more people (real horse owners, actively shopping, not wannabe fantasies) who say “anything but a gray,” than peole who actually want a gray. I have two grays, but I bought both of then IN SPITE of their color, not because of it.

Also, now talking specifically about Connemaras, the organization, and most of the breeders, prefer non-grays. I hear many breeders complaining “we have too many grays”, and none saying “we need more grays”.

[Texarkana]

Oh, I agree most educated and experienced horse owners and breeders do not care for gray.

But in an open market, (dealers, traders, rehomers, auctions, rescues, etc.) gray almost always moves faster and at a higher price than non-gray. That desirability would likely keep melanoma gray genes in the genetic mix.