Genetics for coloured foals

F

Foxfolly

Well-Known Member
Joined
20 January 2008
Messages
1,080
Location
Thirsk, North Yorkshire
Visit site
I know some of you on here know about this sort of thing....

I have heard if you want a coloured foal from a solid mare then Chestnut mares are the best colour to go for....is this right?

We have put our chestnut mare to a coloured stallion who has produced 80 ish % coloured foals to a mixture of coloured and solid mares, so fingers crossed for our coloured colt!!

SO what are my chances of getting a coloured foal from a Grey mare?

I am thinking of buying a really nice looking grey mare who is currently in foal to a coloured stallion. I am then considering sending her to Free Spirit (Coloured Jumbo son) once she has foaled this year.

If the likelihood of a coloured from her is low then I would take our chestnut to free spirit instead then the grey can go back to the other coloured stallion Icon's Immage who we have a free covering for!! Not that you need to know that bit but... well you do now!!
tongue.gif
 
Most coloured mares and stallions in this country are heterozygous - this means with each conception, you have a 50/50 chance of the foal inheriting the coloured gene (tobiano).
If one parent is homozygous, it will always produce a coloured foal. Adverts claiming a stallion throws 80% colour etc are misleading. Every conception goes back to a 50/50 chance.

the base colour of the mare has no relevance as to whether the heterozygous coloured stallion will pass on his tobiano gene. Your grey mare has a 50/50 chance of passing on her grey gene (assuming she is heterozygous grey) so you might end up with a coloured foal that greys out (often called blue and white in the UK)

There is an unproven theory that black and bay is linked to tobiano in someway in warmblood breeding, but totally unproven.
 
At the most basic level...
A horse will be either homozygous or heterozygoes for coloured. A homozygous carries a "double dose" of colouredness, and a hetero carries a "single dose". A "double dose" has no choice but to pass on one of their "doses" therefore every foal will be coloured. A stallion throwing anything other than all coloured foals will therefore be a "single dose" and so it's 50:50 whether you'll get the colour or not from him.
Grey is similar, because they are also either "homozygous"
or "heterozygous", so a homozygous grey will always have grey foals. Problem is, you can't tell by looking whether they are Hetero or homo!
In terms of getting a coloured foal from a coloured stallion with either a grey or chesnut mum, it will depend on chance with a heteozygous stallion, and is a shoe-in with a homozygous one! (But with a grey, you have the same odds on it being grey too.)
There are of course a whole heap of additional complicating factors, this was as simple as I could make it.

Edited to add... a quick way to tell if a horse is heterozygous (say for skewbald)... if one parent isn't skewbald, then it is definitely heterozygous! (But if both are skewbald, it could still be heterozygous; sorry, said it got complicated).
 
Basically your grey mare and your chestnut mare have the same chance of having a coloured foal to a hetrozygous coloured stallion, the grey mare may also pass on her grey gene meaning the foal if coloured would be classed as Blue and White and will grey out. ANY solid coloured mare and a hetrozygous stallion will be 50% likely to have a coloured foal. the grey mares foal will have a 50% chance of being grey also. If you put either mare to a Homozygous stallion you will get a coloured foal from both mares however the grey mares foal can still inherit the grey gene. I understood it best from this diagram

Tt = Hetrozygous Coloured
TT= Homozygous coloured
tt = plain

so if the foal get the T gene from the coloured stalion it will be coloured if it gets the t it will be plain, as the mares are plain they cannot get the T (coloured) gene from her.

As my mare was hetrozygous coloured same as the stallion I had a 75% chance coloured and 25% Plain

Tt = mare
Tt = Stallion

So combinations could be Tt tT TT or tt where T is present = coloured so three occurances of T and one without T so 75% coloured and 25% plain.

Hope that makes sense!
 
Just curious about this, what happens when a grey tobianos or other coloureds finally go all white? Can you still show them in coloured classes?

If not then I would be thinking of avoiding using greys when breeding with colour in mind.
 
My previous horse was a blue and white mare, I had her for nearly 3 years and her blue bits went a lot lighter just in that time, but you could still see the pigment in her skin...

Especially when I scalped her with my extra fine clipper blades a little late in the year, then the poor thing got sunburn on her pink bits cos we had a hot sunny spring!!!
blush.gif
 
That would make sense as grey works on hair and not skin pigment, poor thing must have been cold!!!

Out of interest do grey coloureds suffer as much with melanomas as solid greys?
 
You must log in or register to reply here.
Top