Colour query

[First Time Mum]

I was under the impression that a homozygous black stallion would always throw offspring that were black is that correct as have been looking at a homozygous black stallion with bay offspring???
Thank you x

 

[lillith]

A homozygous black horse will always throw a black based foal, black or red (chestnut) based is controlled by the Extension Locus (locus = location/gene), a horse can be EE = Black, Ee = Black or ee = Red so an EE horse (homozygous) will always pass on at least one E to the foal making it heterozygous or homozygous black depending on what the other parent passes on.

Bay is controlled by a second locus - Agouti, AA = Bay, Aa = Bay, aa = not bay (it is a little more complicated than that with brown and wild bay involved but they are not really relevant in this case). Any horse with a black base and at least one A allele will be Bay.

So a stallion could be EE aa and throw almost always black foals but if the Mare is AA or Aa she could pass on the bay gene making a bay foal. Not the stallion's 'fault'. Hope that helps.

 

[First Time Mum]

Thats great my mare is chestnut and is through the majority of her bloodline so am assuming she is ee.
From what you have said can I assume that a homozygous black put to my mare will always through a black foal? She is a full tb if that helps.

 

[Aidey]

Not a colour expert but I understand that a homozygous black stallion will only throw black or bay foals as he doesn't carry the chestnut gene.

Have a go at this:

http://www.horsetesting.com/CCalculator1.asp

I suspect the foal would be bay as the chestnut would then 'dilute' the black so to speak? If not i'm sure someone will correct me if I am wrong. That and depending on your mares gene's obviously

 

[Sportznight]

If bred to a homozygous coloured or grey, then a homozygous black could through piebald/bay skewbald or grey. Just cannot sire anything based on a red coat (Chesnut/palomino/ginger skewbald etc). I think a dilute gene can have an effect though - so smokey black/buckskin a possibility.

 

[amy_b]

Not a colour expert but I understand that a homozygous black stallion will only throw black or bay foals as he doesn't carry the chestnut gene.

this is correct.
if I am right....you are most likely to get a bay with a chestnut mare, but *I think* it depends on whether you mare is AA/Aa/aa, if your mare is aa you cannot have black offspring so swings both ways!

 

[Truly]

The Agouti (bay) gene hides in a chesnut coat...so if the chesnut(ee) mare is homozygous (AA) for Agouti she will always produce a bay foal even if the stallion is Homozygous Black(EE) and aa (negative for agouti.)

If the chesnut mare is Aa (heterozygous) she will have either a black or a bay foal depending if she passes the A or the a with the same stallion.

So only if the chesnut mare is ee aa and the stallion EE aa will it guarantee you a black foal..the black foal will be Ee aa

So you always need to test the mares genes before you try

Hope that helps

 

[First Time Mum]

Thank guys that has been really useful!!