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 Post subject: Statistical Question
PostPosted: Mon Nov 17, 2014 11:53 am 
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It is generally accepted that Bay / Dk Bay or Brown are the most dominant colors in TB's. I recently acquired a beautiful chestnut stallion to stand for next year (Thabit); In nearly 10 years of breeding I've only had 3 or 4 chestnut mares, and only ever had four chestnut foals born (out of dozens). But here is my question: What percentage of TB foals each year are chestnut vs other colors? And of those, in each foal year, what percentage of race winners are chestnut vs other colors?

Of note, I have a GORGEOUS chestnut 2013 filly by Albertus Maximus out of my lovely chestnut mare Glenfiddich Fire and I have continuous optimism regarding her. For you color lovers, she has diagonal half stockings (LF RH) a huge blaze and a lighter mane and tail. I named her "Empress Alberta".

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 Post subject: Re: Statistical Question
PostPosted: Mon Nov 17, 2014 9:17 pm 
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I suppose the JC would know,but in general theory since chestnut is recessive to the black based colors ( bay/black/brown) only breeding two chestnuts will guarantee a chestnut foal. Occasionally two black parents carrying a recessive chestnut will produce a chestnut foal. Chestnut x heterozygous black is 50% chestnut foal/ 50% black carrying a recessive red and chestnut x homozygous black = black carrying a recessive red only."chrome" expression tends to be color linked to chestnut so it's a lot easier to get a chestnut with chrome than a black based . I would imagine there are fewer chestnut winners than dark ones just given the fact there are more black based by volume . No official knowledge... But I would hazzard a guess an awful lot of the present chestnuts are related to Mr. Prospector. He was a busy boy...,

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 Post subject: Re: Statistical Question
PostPosted: Tue Nov 18, 2014 10:56 am 
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The best way would be via the JC, but in the absence of that info we can estimate it using the colors of progeny of chestnut sires listed on this site.

If f = frequency of e allele in the TB population, then f*f = fraction of red-based TB's
The offspring of a chestnut sire will have a 1*f chance of being ee and thus red-based. So if we look at the distribution of colors of (prolific) chestnut sires, we can guesstimate f and from that the fraction of chestnuts in the overall TB population. This assumes that the total population color distribution is the same as these particular dams, which is not necessarily a good assumption but let's roll with it.

Based on the produce records on this site as of today:
Giants Causeway: 766 chestnuts / 1496 non-gray offspring with color listed
Distorted Humor: 497 chestnuts / 1008 "
City Zip: 313 chestnuts / 617 "

if we just average all of these, that gives an estimate of f = 0.504
therefore a guess of the frequency of chestnuts in the population = f*f = 25%


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 Post subject: Re: Statistical Question
PostPosted: Wed Nov 19, 2014 8:49 am 
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Chestnuts have the edge that when two of them are crossed,
the resulting foal will always be chestnut. The only "exception"
is when the resulting foal is white, but even on this case, the foal
is still a subjacent chestnut.

Most intriguingly difficult seems to be trying to achieve a black colt!


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 Post subject: Re: Statistical Question
PostPosted: Thu Nov 20, 2014 9:33 am 
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Jorge wrote:
Most intriguingly difficult seems to be trying to achieve a black colt!

Black foals are not difficult to achieve when at least one parent has a copy of the dominant 'E' (black) allele at the extension locus and both parents have at least one copy of the recessive 'a' allele at the agouti locus. They're fewer in number because of the frequencies at which the 'e' and 'A' alleles occur in the TB population.


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