what is a "Lethal White"?

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mad mare1

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Just heard on the marestare website that a foal has been born and they suspect it is a "Lethal White" can anyone tell me exactly what this is, I have never heard of this before.

Thank you
 
A lethal white is a pure white foal - I *think* that lethal white's don't live very long, because they can't pass any droppings and get colic.

Both of the parents have to carry and then pass down the gene. Someone else can probably elaborate though!
 
thank you for that,it seems that virtually any breed can be struck by this very nasty affliction, and I hope, for the mare's sake, that her foal just turns out to be a white baby, and goes onto live a happy life.
 
Lethal white is a congenital condition usually linked to the overo gene.

A foal that has two overo genes linked to the lethal white mutation is called a 'lethal white'. These foals are born white all over; unfortunately their intestines also fail to develop properly and they are usually either still born, die shortly after birth, or are PTS.

It's important to remember that frame overo is not the only gene that can cause foals to be born white in appearance - a maximally expressed sabino will also do that, for example. Breeds that do not carry overo won't be at risk of producing lethal white foals either; so it's not virtually any breed that can be struck, but only those horses carrying certain pattern genes.

It really bugs me that people are still breeding foals which have a risk of this syndrome. There is no need for this to happen. It's perfectly possible to test horses for the lethal white mutation, and avoid breeding those who test positive for the gene to any other horse that tests positive. There is no risk of a lethal white foal from a horse that doesn't carry the mutation; it's only a risk if you breed two horses who both carry it. The test costs about $25 - $30. I would have thought the cost of testing would be nothing compared to the possibility of losing a foal. It's just plain irresponsible to breed two lethal white carriers and then cross your fingers. :(
 
Chev...does this mean that the stallion in question is definately a carrier of the gene?
does this mean that he shouldn't be bred from? or simply that the owners should only allow him to mate with mares which have been tested?

Or is there still a chance of a lethal white if only one of the parents has the gene?

sorry if they're silly questions...just curious to understand it properly. I too hadn't heard of this til this morning.
 
If this foal is a lethal white then yes, both mare and stallion are definitely carriers.

If the foal is not, then it's still possible both horses are, or that one is, or that neither are; the only way to say for sure would be a DNA test for the lethal white gene.

If a horse carries overo, or it's supsected they might, the responsible thing to do is to have them tested for lethal white. That way, you can make sure there is no chance of a lethal white foal (so if you have a mare that tests positive, you make sure she's only ever covered with negative stallions. If your stallion is positive, then you only use him on mares that tested negative. Simple, really.)

For as long as breeders don't test both parents before breeding, they run teh risk of a lethal white foal.

There's no chance of a lethal white if only one parent carries the gene; so all you need to do is make sure you don't breed two carriers together.
 
just seen on the marestare website, the foal died, would they have known that the parents were carriers of the faulty gene? And why would you even risk it?
 
They won't have known *for sure* unless both had been tested.

No, I wouldn't risk it. There's a 25% chance of a lethal white from two lethal white carriers.

Now they know both mare and stallion carry the gene, they are in a position to ensure that both are bred only to tested non-carriers.

Honestly, for the sake of $25 I would be testing regardless of whether it was suspected or not. Even in nothing more than monetary terms, they've lost much more. And the heartache they'll go through now, added to the stress the mare will go through... all for the sake of a £25 test.
 
Hello chev, (thanks for the link to this thread)

Does this mean that every chestnut horse with white markings has to be tested for the lethal white gene. And what about the horses breed from chestnuts with white markings that show no overo patterns, couldnt they still have the genes passed from their parents if the parents have overo genes.
So unless you know the linage of your horse you could be at risk if you breed any coloured mare?


Tracey:confused:
 
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