colour genes

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christine48

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Would you expect 2 full brothers to carry the same colour gene? Just asking because it is said that Contendro1 cannot throw a chestnut yet in the brightwell catalogue there is a chestnut by his full brother contendro11 who is chestnut.
 
Both sire and dam got chestnut in their pedigree. Although they are full brothers they are not monozygotic twins.
 
Slightly off topic but still to do with colour - I had my Sir Shutterfly colt tested for colour & received this very interesting report back:

Horse Name: Delaroche Shutterboy
Lab Ref: 779/8805

Red Factor test result: EE - Homozygous Black. The foundation colour of the horse is Black, and has tested as Negative for the recessive red gene. Therefore when bred, the horse can not produce Chestnut foals, regardless of
mate. 100% of foals will be Black/Brown based.

Agouti Test result: Aa - Heterozygous. The horse is positive for the dominant Agouti/Bay gene, this further modifies the Black base coat to the Bay colouring, therefore the horse can be considered Bay based, the horse will pass the Agouti/Bay gene to 50% of foals when bred.

Grey test result: gg - Negative. The horse is a non-carrier of the grey fading gene.

Evaluation: The horse can be considered bay, with the genetic potential to produce a mixture of both Bay and Black foals with a 50/50 likelihood each time, mating to a Bay mare will increase the chances of a Bay foal to 75%. The horse can't produce a chesnut foal, regardless of pairing. The horse has been confirmed non-Grey, so won't fade out, nor will he produce any grey foals (unless the mare is a grey carrier.)

The horse is conceivably a Bay-Dun, there's no test to confirm the presence of the Dun gene, however it can be visually confirmed with the presence of dorsal/zebra barring. Given the parentage, if the horse is a Dun carrier,
he is likely Dun Heterozygous (Dd) meaning that he'll pass Dun to one half of his offspring.
 
There are caveats to your results, unless the horse was tested by pet DNA in the USA then it should be described as Bay or Brown. A would be a bay but At a brown (black and tan).

The 50:50 likelyhood each time is only what that horse will put forward to the mix, if bred to a partner who is AA AAt or AtAt you will never get a black and many chestnuts are homozygous for the agouti genes (All of mine bar one not yet tested are !!!!!!).

"mating to a Bay mare will increase the chances of a Bay foal to 75%." This could increase it to 100% if bred to a chestnut or bay/brown mare who has two Agouti genes.

UC Davis in the USA have a dun zygosity test but it is not a full DNA test and quite frankly you can usually work it out for yourself!
 
We did work it out for ourselves - he started losing his foal coat & wasn't showing any signs of going grey (dam is grey). So we surmised that the very pale colour & dorsal stripe he was born with might be here to stay. I really wanted the test doing to confirm the fact that he wasn't grey, the rest is just an interesting addition.

UC Davis did say they would happily test him for the Dun gene but that as he is a warmblood it might not be conclusive - so decided against.

Do you have any suggestions as to where his Dun has come from - link to pedigree:
http://www.sporthorse-data.com/db.php?i=10549952&time=1249121446

http://www.youtube.com/user/DelarocheStud#play/all/uploads-all/1/kxSuuugD3i8
 
Would it be dun factor, or the countershading that some bays have? Would need to see more specific dun markings really. Any more pics?
 
I think you can rule out the sire's side unless he has produced anything similar? They all look black and tan or bay and there are plenty of pictures on that side.

It could be hiding behind the grey somewhere back in Randi, Mandy was from two browns so ulikey from her. Has Randi produced ay dun like foals?
Duns are typically born pale, mine was sort of a lilac colour then turned dark (signature below). I beleive there are a lot of dilutes being found behind grey in the iberian breeds. Historically the PRE favoured colours were chestnut bay and grey, and they set about breeding those colours, so that is probably where the dilutes have been hiding over the years, they did get rid of the coloureds though.

Or it could be Damour and Pincabella, do you know what colour they were? Damour has the U/K ped and it could be that there was a dun in there? Looking at the picture of Birthday Girl, it looks like a hint of a dorsal stripe? Have you any pictures of her when she was younger? The trouble is people rarely note what colour greys are when they were born, which is so helpful!!

Dun's are usually pretty obvious when mature unless you have appaloosa coat patterns which a bit like grey hide all the clues!
 
Sorry to hijack the thread
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but, my grey filly has a very distinct dorsal stripe; does that mean she has the dun factor?
 
It’s only really an indicator if there is also dun in the pedigree. Dun is a dominant dilute that will show even on dark coats if you look closely, once lost the only way to recover it is to breed back to a dun. The real tell with duns is the mane and tail hair and the sometimes very feint additional wild markings. This isn’t a brilliant picture but it’s the only one to hand! You can just see the different colours in the tail hairs, Spike has not got strong primitive markings but you can see them when he is clipped, he has darkening across the withers, cobweb on the forehead and feint leg barring. He is genetically a Bay carrying chestnut and Black and Tan. Ee AAt. An has one copy of the Dun gene from his father who from his limited number of progeny was thought to be a homozygous dun (hidden somewhat by his appaloosa coat pattern – all 9 of his foals were dun).

This one is strange as he has definite chocolate coloured areas where they should according to theory be black! Before I tested him this colour was theorised as a dark red dun and I can see why.

IMG_1035.jpg


The problem is some bays (probably black and tan’s more than bays) have black across the spine that in some is narrow like a dorsal stripe in duns. It could be a left over primitive marking when the mutation to bay took place and still be a separately inherited dorsal stripe linked to bay and or black and tan, it could be down to sooty factor, if that exists in its own right or it could be the most minimal appearance of black and tan, where the black is pushed back to its limits on the extremities. Hopefully some enthusiastic scientist will find out for us one day!

With the grey it is sometimes more difficult, it could be that possibly being a black and tan underneath the spinal hairs are the last to grey? What colour was the filly when she was born?
 
I *think* she was chestnut...... bought her as a foal, and she was much more rose coloured then, and a lot darker. Mum was chesnut and dad grey.

Thanks for all that info
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it's all very complicated though isn't it
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It's like with everything to do with horses, the more you know, the more there is to know!
 
Oh yes it's complicated and will probably get worse as I think they will find loads of colour genes! My spreadsheet will probably collapse soon as it is!!!
 
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