Homozygous Grey vs Heterozygous Grey <PIC heavy> - The Horse Forum
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post #1 of 28 Old 01-14-2012, 07:29 PM Thread Starter
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Homozygous Grey vs Heterozygous Grey <PIC heavy>

Okay, so do any of you know if homozygous greys turn nearly white at a faster rate than heterozygous greys?

My brain wants to think that if a horse inherits two grey genes, that it would then quicken the pace to turn nearly white. Maybe this is helped by my experience of growing up with heterozygous greys (my family bred a few grey mares to non grey stallions) and the grey foals took time to get really light, some were teenagers before they turned super light grey.

One of the mares we bred, my mom had bought at auction as a long yearling. No idea of her parentage, but she was a very light grey when we got her. I really think that she is homozygous grey, had three grey foals, all born sorrel/chestnut.

The first two pictures are from when she was about 1 1/2 to 2 years old

Mysti 3.jpg

Misty a long time ago.jpg

Then as a 5 year old with her first foal, she never changed color by this point (couldn't get any lighter) and has only aquired a few flea bitten spots

Misty 1990.jpg

Misty 1990 undersaddle.jpg

Now what of her third foal? (also her last foal) This was the only time that the above mare, Misty, was bred to a grey stallion (registered arabian, ee, heterozygous grey). I personally believe that Glory only recieved one grey gene.

Glory on her second birthday. Like her party hat?

Glory's birthday.jpg

She is about 3 years old here, I think...

Glory 1997.jpg

Riding along the Seattle coast on the other side of Misty, as a four year old

riding at the beach 1998.jpg

You can barely see her on the other side of Misty.... again
But she is 7 years old here and still has a darker mane and forelock, as well as darker legs than that of her dam (both wet from a bath)

August 2001.jpg

So, I am of the opinion that since it took Glory a lot more time to get nearly white (she is very flea bitten and is turning 18 this spring) that she is a heterozygous grey, where as her dam was white as a ghost at an early age.

Is there any logic behind my thinking?

The reason I am asking is because I am hoping that she is a heterozygous grey and is possibly able to give my sister a non grey this spring -would certainly stand out from her white and nearly white mares (she owns both Misty and Glory)

Just realized that my sister that owns Misty and Glory appears in every picture that has people in it
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post #2 of 28 Old 01-14-2012, 07:33 PM
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Statistically, homozygous greys do seem to whiten earlier. HOWEVER - those statistics are collected from hundreds of horses, and there are MANY horses that defy the trend. So while the statistics suggest it, using the time taken to grey out to determine zygousity is never going to be a foolproof method.

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post #3 of 28 Old 01-14-2012, 08:06 PM
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easiest way to figure out is to do a UC davis color test on her for grey. its super quick and all you have to do is send in hair. We have a heterozygous grey mare. She didnt grey out until 11 and was still pretty black at 9. she has had 4 foals. two grey. two not. sire on all four was not grey
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post #4 of 28 Old 01-14-2012, 08:36 PM
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I think what you said is generally true, but I have no real expertise on the matter. But I DO own two grays at the moment, and I'm sure they have to be heterozygous because each has only one gray parent. They are a mare and her colt and they are both slow to gray out.

The mare I have only had a couple of years, but she is going on 18 and she still has some dapples on her flanks and the underside of her belly. Her colt is 1 1/2 years and most people still don't believe he is a gray but I'm sure he is because he has roaning on his face and white in his tail. But other than that, he looks like a bay at first glance. His sire was chestnut.

So I guess what I'm saying is in my "sample of two," heterozygous grays do tend to gray slow.
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post #5 of 28 Old 01-14-2012, 08:41 PM Thread Starter
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I think that if we did a UC Davis color test, that I would definately also test for agouti. Glory is bred to a solid homozygous black arabian, so the agouti would affect whether she would produce a bay or black foal.

I can conclude that Misty has atleast one agouti gene that could be passed to Glory, because of her first foal. The first foal -pictured with 5yo Misty- was by a solid black (Ee) qh stallion, and when she grew up, the filly was then bred to a solid homozygous black and produced a beautiful bay colt. He didn't inherit his dam's grey gene, and stayed bay :)

The end of April can't get here quick enough to find out what is growing in her belly :)
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post #6 of 28 Old 01-14-2012, 08:54 PM
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Very exciting! You just HAVE to post pictures the day that baby pops out!
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post #7 of 28 Old 01-14-2012, 08:58 PM Thread Starter
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Maybe for some more reference, these are Misty's first two foals. Both are heterozygous grey by the same black quarter horse sire.
Chip and Saigar.jpg
Chip is on the left, 4 years old, was a dark chestnut foal.
Saigar is on the right, 5 years old, was the foal pictured at Misty's side

Chip went through a large range of weird colors before he turned nearly white as a teenager. Saigar went light about as quickly Glory did, but retained some darker areas just like Glory did.
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post #8 of 28 Old 01-14-2012, 09:13 PM Thread Starter
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Originally Posted by trailhorserider View Post
Very exciting! You just HAVE to post pictures the day that baby pops out!

That I shall!

Here is what what looked like on Jan. 4th with her growing tummy.
Glory 1-4-12.jpg
^^finally, Misty is behind Glory
Glory rear 1-4-12.jpg
Yes, she is fat and over weight, has been on a diet for two years (she gets fat from looking at food).
Not bad for an 18 year old maiden mare though

My avatar is the sire of the coming foal
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post #9 of 28 Old 01-15-2012, 12:31 AM Thread Starter
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here is Chip when he was 8yo
Chip 1999.jpg

Then when he was 14yo
Chip 2005.jpg

Saigar when she was 7yo
Saigar 1997.jpg

Both of them could only have had received a grey gene from their dam, Misty. Saigar went light so much faster than Chip, who did eventually get to a light grey...

I still think that Glory could be heterozygous grey (I really do hope). But since neither her of her dam's other foals got more than a few flea bitten spots, would that have actually have come from her very flea bitten sire? I have no idea why some grey horses get heavily flea bitten and others do not. Glory's sire was a heterozygous grey that was quite flea bitten, does Glory's flea bitten body then mean that she is a homozygous grey because her sire gave her the grey gene as well as her seemingly homozygous dam?

Where do flea bitten spots come from genetically?!? Is it linked with a particular horse's grey gene, or are some just more prone to becoming flea bitten than others without being linked to a particular horse's grey gene?
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post #10 of 28 Old 01-15-2012, 12:53 AM
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Very nice grey horses

Country Woman

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breeding , color , grey , homozygous , question

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