lethal

[skewpie]

Chev or anyone can u help?
whilst checking out foal colours i came across the term LETHAL what does this mean?

[pineapple]

im not sure but i think its like a pure white horse, but i think i dies almost as soon as being born..... not sure though, but i think ive heard that before.

[chev]

It's Lethal White Overo Syndrome. It happens when a foal is homozygous for the frame overo gene (has two copies of it) and nothing to do with dominant white horses.

In foals who have two copies of frame the gut fails to develop properly and they are either born dead, die shortly afterwards or are PTS before they die naturally. They cannot survive; which means it's really important to test for the gene if breeding a horse that might carry frame. Problem is that some frame horses have really minimal markings. DNA testing will confirm one way or the other if a horse carries frame. If they do, it's advisable not to breed them to another frame; the chances of a LW foal are 25% from that cross. Not good odds.

[Stormin]

Are certain breeds of horses more "prone" to this condition or are all horses potentially at risk ?

[chev]

It is mostly associated with overo patterned horses (frame) but there have been cases of tobiano/overo horses, solid breeding stock Paints from overo parents, and some QH who have no obvious pattern.

If there is any chance at all a horse might carry the gene (colour in either parent, for example) it would be a good idea to test. Genetic testing means you know for sure whether or not your horse is a carrier; better to pay for testing and know than run the risk of a LW foal.

[pineapple]

ah so they a not actually white:o, but they do die and its impossible for them to survive??

[chev]

Yes, they're born white with blue eyes; some may have a few spots of pigment here and there but very few. But yes, they do all die; the gut just isn't formed properly and those who don't die soon after birth will end up dying or PTS after showing colic symptoms.

[skewpie]

thanks so much id been checking foal colourings for my historic and a black overa stallion will keep an eye open for this now:D im going to post a new thread on about the colour of my roan cob i have never seen a mix like this she is in foal to the black overa