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

[prunebey]

“Slow graying” vs “fast graying” is something I had never heard of until late last year, and I find it fascinating. Youtuber Megan Elphick has a ConnemaraXWarmblood that is going gray, but still pretty much looks like like a bay with roaning at almost 7 years old (along with a gray streak in her tail). Her 11 year old Connie dam seemed to gray out at a much more “normal” rate.

I had an Arab mare (assume “fast graying”) that I lost to internal melanoma this past September (guesstimate age was 34). First external sign was about 10 years ago, and she had surgery to remove a rather large anal area tumor in 2016. Always loved grays, but I’ll never own another. Went through way too much over that 10ish year span that I never want to deal with again.

[Posting_Trot]

I’m also interested in the question of whether the likelihood of melanoma is affected at all by the base coat color. So my mare was coal black when she was born. When I bought her at age 7 (almost 8) she was definitely gray but with very pronounced black points and dapples. Now at age (almost) 15, she is quite light, and her legs have also lightened substantially.

So, does a bay that goes gray, for example, have a different chance of melanoma than a coal black horse?

[Ajierene]

@Janet - I am not sure where the information on age and melanoma growth comes from. At first I thought maybe it was a predominant Connemara trait but in looking up articles, I found one from the ACPS that indicates horses can start growing melanomas over 11 years of age.

Other scientific sites seem to say they can start developing after age 11 (disclaimer - some of these pictures skeeved me out so I skimmed some articles way more than I normally would)
https://equinesarcoid.co.uk/melanoma-in-horses#:~:text=Horses%20can%20develop%20melanoma%20at,implications%20for%20the%20horses%20welfare.
https://ceh.vetmed.ucdavis.edu/health-topics/melanoma-horses

https://acps.org/melanoma-myth/

[Ajierene]

As far as continuing to breed gray horses…well, there are paint breeders out there creating foals with the lethal white foal syndrome because 75% of the time they breed a horse with one copy of the mutation to another horse with a copy of the mutation, they get a perfectly healthy and sought after foal.

As mentioned before, one copy of the HYPP gene is considered “fine” to many quarter horse breeders. PSSM is another one that is not seen as the issue it could be.

Fast thoroughbreds with feet falling apart are still sent to the breeding shed to create more, hopefully faster horses with potentially even more brittle feet.

Breathing problems in Arabians with overexaggerated noses.

Dwarfism in miniature horses.

So many defects/mutations that are prevalent in the horse (or any animal) world due to human preference or hope for something.

[Janet]

@Ajierene

@Janet - I am not sure where the information on age and melanoma growth comes from. At first I thought maybe it was a predominant Connemara trait but in looking up articles, I found one from the ACPS that indicates horses can start growing melanomas over 11 years of age.

Based purely on UC Davis’s request for samples in the 3 age groups

• Developed melanomas befre age 6
• Developed melanomas betwwen 6 and 11
• Melanoma free after age 11. (fixed typo)

[Ajierene]

@Janet

Based purely on UC Davis’s request for samples in the 3 age groups

• Developed melanomas befre age 6
• Developed melanomas betwwen 6 and 11
• Melanoma free at age 22.

Is there an article or research conclusions on this? This sample request indicates to me that it is a “given” that gray horses develop melanomas after age 11 since no samples are requested for horses with melanomas that developed starting age 11.

Like that’s the constant (can’t think of the proper word right now).

[Janet]

@Ajierene

Is there an article or research conclusions on this? This sample request indicates to me that it is a “given” that gray horses develop melanomas after age 11 since no samples are requested for horses with melanomas that developed starting age 11.

Like that’s the constant (can’t think of the proper word right now).

That is a possible interpretation.
BUT
In the presentation the UC Davis team gave to us (ACPS BoG) last year (2023), it was clear that they were using the “melanoma free after age 11” group as the control group for comparison - these are the genetics that DON’T lead to melanoma. It was a powerpoint presentation, so I do not have a citation.

I interpret it as a “given” that “horses don’t develop their FIRST melanoma after age 11”.

[Ajierene]

I’m not privy to this presentation so…yeah…I’m going to have to go with all the research I am seeing that indicates horses can develop their FIRST melanoma after age 11.

[Janet]

I am making my way through the linked “Nature” artricle.

I don’t understand all of the genetic technical terminology, but I can follow the conclusions. There are several relevant points.

The “slow graying” genetic variant, aka G2, is relatively rare. They only found two groups - a family of Connemaras in Sweden and a family of 5 TBs in Japan, with the G2 versions. MOST grays have the G3, or “fast graying” variant. (Note that they use the term G1 for the non-gray variant)

The “slow graying” horses maintain their “base coat” color, but getting lighter, until their teens. They only start to look dappled gray in their late teens, and never lose the dapples, even at age 30. " If a slow greying foal has face markings (like a star or blaze) the white parts are not well-defined and the white hairs will spread out in time." “The first signs of greying in a slow greying horse will normally not appear until 5–7 years of age, with grey hairs often expanding from white head markings.” “When a slow greying horse has reached an age of about 15 years the coat color may turn into a dappled steel or bluish grey shade.” “…they will never become a visually white horse.”

Within both families there were some descentants with the slow graying variant, and some with the fast graying variant. They examined 25 “late graying” horses between 15 and 35 and found no sign of melanomas on any of them.

In the general population, 50% to 80% of gray horses in this age group show signs of melanoma. Even though they only examined a small population of “slow graying” horses, this difference is statistically “highly signifcant” ( Χ 2 = 25.0, d.f. = 1; P = 6 × 10-7).

One of the conclusions is:
“The G1/G1 genotype shows no greying and low incidence of melanoma, G1/G2 shows slow greying and low incidence of melanoma, G1/G3 shows fast greying and high incidence of melanoma, and G3/G3 homozygotes grey very fast and show a very high incidence of melanoma as previously demonstrated.”

[Zevida]

@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’ve had two grays who didn’t develop external/visible melanomas until their late teens, so no I don’t think you can assume even at 16 she won’t develop them.

[Posting_Trot]

Yes, that’s definitely the takeaway point I’m getting from the discussion. Too bad!

[Willesdon]

As an outsider, I have noticed that American horseman are a) set against grey horses and b) very concerned about melanoma. In the UK, a) grey horses are very popular and b) melanomas are seen as a manageable problem and certainly not a deal breaker in a horse purchase. Maybe it isn’t just coat colour but rather physical environmental variation that causes melanomas?

Some days when watching Eventing it is “Yet another grey… And another… And another… Oooh, here comes a chestnut”.

[Zevida]

I loved my greys and I think it’s a beautiful color and I mostly wouldn’t want another due to the pain of trying to keep them clean or the extra work to get them cleaned up and looking nice. But if the perfect unicorn for me was grey, I wouldn’t turn it down because of that.

[Haven_tJumpedInALongTime]

I appreciate everyone who shared their thoughts and experiences!

[poltroon]

@Janet

The “slow graying” genetic variant, aka G2, is relatively rare. They only found two groups - a family of Connemaras in Sweden and a family of 5 TBs in Japan, with the G2 versions. MOST grays have the G3, or “fast graying” variant. (Note that they use the term G1 for the non-gray variant)

The Connemara stallion *Canal Laurinston was certainly a slow greying horse; he didn’t look grey at all until he was older and he also did a funny reverse grey where his muzzle was the last thing to grey out. He was imported from Ireland and stood in Northern California for many years, siring many unusually colored greys. Do you happen to know if any of his grey offspring were included in the study?

A picture of him in his late teens is here: https://www.equinetapestry.com/post/ponies-don-t-read

[poltroon]

@Janet

That is a possible interpretation.
BUT
In the presentation the UC Davis team gave to us (ACPS BoG) last year (2023), it was clear that they were using the “melanoma free after age 11” group as the control group for comparison - these are the genetics that DON’T lead to melanoma. It was a powerpoint presentation, so I do not have a citation.

I interpret it as a “given” that “horses don’t develop their FIRST melanoma after age 11”.

My guess would be that these groups were set up to make the statistics right and the sampling manageable, but that it’s a highly educated guess. It’s probably not the case that horses never develop them later in life.

I don’t know how much has been done to accurately categorize age at melanoma in older horses given that we’re generally told to leave it alone. I also wonder how common it is for horses to develop internal melanomas before external ones.

[Texarkana]

@Willesdon

As an outsider, I have noticed that American horseman are a) set against grey horses and b) very concerned about melanoma. In the UK, a) grey horses are very popular and b) melanomas are seen as a manageable problem and certainly not a deal breaker in a horse purchase. Maybe it isn’t just coat colour but rather physical environmental variation that causes melanomas?

Some days when watching Eventing it is “Yet another grey… And another… And another… Oooh, here comes a chestnut”.

I don’t have the link handy, but there is evidence that different breeds carry different variations/duplications of gray genes like the OP said.

Because I agree with you on some level— I grew up with Arabians in the US. Most of them were gray. Most of them got melanomas in old age under their tails, etc., but they were never a problem. Our horses lived into their late 20s and 30s, dying of typical old age causes.

In the years since then, I have had so many negative experiences with melanoma ending the lives of gray horses early as young as 6 years of age. A lot of these were TBs, but not all.

[Janet]

@poltroon

The Connemara stallion *Canal Laurinston was certainly a slow greying horse; he didn’t look grey at all until he was older and he also did a funny reverse grey where his muzzle was the last thing to grey out. He was imported from Ireland and stood in Northern California for many years, siring many unusually colored greys. Do you happen to know if any of his grey offspring were included in the study?

The family of Connemaras used in the study were Swedish, all connected to “Hagens D’Arcy (stud book number RC 101) in generation 5 whose mother was fast greying and whose father greyed slowly.” There were 22 in that group.

But it certainly looks as if *Canal Laurinston was another slow greying horse.

His family doesn’t seem to be in THIS study. But there is ANOTHER Connemara specific genetic study about grays and melanomas at UC Davis. If you send me a message with YOUR email, I can put you in touch with the woman who is the contact between UC Davis and the ACPS for the study.

[Posting_Trot]

That’s a beautiful horse!

I love grays.

[skydy]

I’ve noticed some very big differences in the greying of yearlings from a few TB sires. This is from my derail on the Dressage forum awhile ago:

Off topic a bit, but it is interesting to see the difference in young grey horses.

In some TB sire lines, the differences in their grey yearlings is significant. It’s not a hard and fast rule for each stallion of course, but many grey yearlings by Tapit look like this; https://vimeo.com/762824182

Whereas many yearlings by the late stallion Arrogate looked like this;https://www.youtube.com/watch?v=c5xlBjoYXnw

Very different grey coloring of the get of each horse.

Sorry for the derail, just mentioning that grey has no all encompassing rules of progression.