Colour Genetics help please

[tinkerdorisalison]

My dales pony mare Rosebarr Sara is grey and has produced two grey foals from our boy Wtaerside Jack who is black.

I know grey is a dominant gene for dales but what if she were to be covered by say a Freisian who are all black?

what colour would it be?

[Anna]

I would guess 50/50 chance (although it depends on Sara's breeding (i.e is she out of black/brown/grey genes and what parts of them she carries). Even with the frieisians you still get the genes from the mum and dad to make the foal, its just with Friesians you only ever cross black to black.

I think. I await a more educated reply though from our genetic clever people!

[lucydales]

You need Heather or Helen!

I believe if she has two grey genes, all foals produced will be grey whatever colour or breeding the stallion.

If she carries only 1 grey gene then it will be a 50% chance of a grey foal, 50% chance of another colour. She may have bay genes?

What colour were her parents and grandparents?

[cadeby]

I looked Sara up on Grassroots and saw that her sire Broscoe Joseph was black. Therefore, Sara must be heterozygous grey (ie. she only has 1 copy of the grey gene).

So there is a 50:50 chance of a grey foal, regardless of the colour of the stallion you choose.

As Lucy and Anna say, depending on the genetic basis of her base coat colour, she could surprise you with a bay/brown foal (like Nipna's Trevor, now with Zelda - grey sire, black dam )


On a slight tangent - research by the University of Uppsala in Sweden carried out in 2008, now suggests that 75% of grey horses will have melanoma by the time they are 15 years old, but the incidence is highest in homozygous greys (ie. those with 2 copies of the grey gene - one inherited from each parent).
They suggest it may be preferable (as a welfare issue) to NOT breed grey to grey, thus reducing the possibilty of producing homozygous grey horses, and lowering the risk for melanoma.

I used to breed Percherons (which in accordance with the breed standard can only be grey or black). Had this research been available at the time, I think I personally would have always selected a black Percheron stallion for my grey mares.

I don't have any grey Dales mares, so it's not a decision I now have to face, but it's an emotive topic no doubt and raises the issue as to how much we allow an increased knowledge of equine genetics to influence our breeding choices, particularly with a rare breed like the Dales

[harveydales]

Helen - that's very interesting. Thanks for psoting.

[SuzieP]

Very interesting stuff. Helen, IMHO that research re melanoma in greys deserves a new thread to highlight it.

[heathera]

Thanks for posting Helen. I too would never buy a grey now if I knew him/her to be homozygous. I know Drummer wasn't and the vets said his case was incredibly rare but it worries me all the same.

The overwhelming majority of grey ponies develop these small melanomas and live with them for a decade or more before dying of something totally unrelated so I wouldn't say it's a reason to never breed grey ponies but I think not breeding grey to grey is a sensible precaution.

I can look out the research I did when Drummer was diagnosed and post up a thread if you want?

As a quick aside I'd worry a little about breeding a Dales mare to a Friesian stallion as both breeds have large shoulders and most of the UK Friesian stallions are above 16hh which means you might foaling problems. I'd at least ant to be on very close foaling watch and ready to help if I did this breeding. I know Tinkerdorisalison will have taken this into account with her choice of breeding mare and stallion but I thought it worth highlighting in case any novice breeders are reading this.

[heathera]

May 14, 2011 9:58:03 GMT -1 Minnie said:

Am I right in saying it's a 25% chance of breeding a homozygous grey from two grey parents and 75% heterozygous, Heather?..I think that's right isn't it? I've had limited sleep and it's showing this morning

I'm just going to blame my age if I'm wrong but I think you're right if I remember my Mendalian stuff correctly

[cadeby]

May 14, 2011 9:58:03 GMT -1 Minnie said:

Am I right in saying it's a 25% chance of breeding a homozygous grey from two grey parents and 75% heterozygous, Heather?..

Almost

Crossing 2 heterozygous grey parents statistically gives :

25% homozygous grey GG
50% heterozygous grey Gg and gG
25% non-grey gg

[cadeby]

The non-grey (gg) is actually homozygous, so it's still not 75% heterozygous, just 50%

[tinkerdorisalison]

Thanks guys - as usual expert advice ;D

the reason I asked was a friend has Sara on a loose loan arrangement at the moment - she mentioned about breeding and I said I would consider it. I would prefer she bred a dales really.

At the moment she is more of a 'big horse' lady but Sara is steadily convincing her ponies are best!!! ;D

[cadeby]

I think Heather made a very valid point about shoulder size.

There is Friesian Stud in the next village to us. They have some stunning horses! I went to an Open Day there a couple of years ago and was chatting to the owner. She said that they have to manually assist with the delivery of the foal's shoulders in over half of their mares
I'm not sure if this was vital, ie. to enable the delivery to actually proceed, or was done just to help prevent tearing of the mare?

Hopefully that will sway your friend to either sticking with a purebred Dales or going for a "smaller-shouldered" cross

[cadeby]

May 14, 2011 9:58:03 GMT -1 Minnie said:

.... I know there have been cases of melanomas in bays and bay roans too within the dales.

Any colour of horse can develop melanoma, and bays or bay roans are no more likely to get it than, for example, a black.

The only colour proven to carry an increased risk is grey and current research is trying to discover if the mutation which causes this cancer is somehow specifically "linked" to the grey gene.

Infact, the horses with the highest proven risk factor are homozygous greys (GG) which are also homozygous recessive for the bay Agouti gene (aa).
By contrast, grey horses which are heterozygous for agouti (Aa) are less at risk of developing melanoma. Thus, having a bay gene seems to afford protection and definitely does not increase the risk.

I think the owners of the bay and bay roan Dales ponies that Evie has mentioned must just have been unlucky If they owned black Dales Ponies there would be an equal low risk.

Quarter Horses, Arabs and Thoroughbreds are also thought to show an increased risk for melanoma regardless of whether they are grey or not, which suggests there may be a breed factor involved too. Time and further research will tell

[Fi]

This is a fascinating topic - hopefully there will be more research on these sort of gene linked issues.
I have to say, as a prospective Dales buyer, I'd avoid a grey. Not just due to the melanoma risk, but it's definitely a factor.
And interesting comments about breeding to a Freisian - an acquaintance of mine is considering putting her coloured cob to one and will I'd guess run a similar risk.

[DalesLady]

fascinating!