View Full Version : overo lethal white syndrome
22nd Mar 2002, 05:56 AM
i was reading an article on the internet about "overo lethal white syndrome" ... for the life of me i couldn't understand the complicated genetic terms they were using :confused: what is lethal white syndrome, in plain english?
22nd Mar 2002, 08:32 AM
All individuals inherit one set of genes from their father and one from the mother. An animal can have one gene that codes for overo lethal white syndrome without any problems arising, but if they inherit the gene from both the father and the mother, they will die a few days after the birth.
I don't know which genetic terms you are wondering about, if you list them, I will try to answer. (I'm not online again until Sunday or Monday, though.)
22nd Mar 2002, 09:19 AM
what is the address of the website the report was on??
23rd Mar 2002, 10:00 AM
In as plain english as I can muster :)
A single Oo gene gives overo, an O+ gene gives non-overo.
So... overo horses must have this one gene.
If a overo is bred to an overo there is a possibility that the foal may have gained the Oo (overo gene) from both parents.
Now this makes the foal a lethal white as it has a double up of the overo gene. Therefore an overo carrier should not be bred to an overo carrier.
I hope this makes sense. I have found colour genetics very interesting after reading a very easy to read book 'Horse colour explained' by Jeanette Gower. It did take me quite a few reads to get a clear idea of the principles and ideas but it is one of the most plain spoken books on genetics I have found, I would recommend it if you can find it.
23rd Mar 2002, 03:54 PM
heres some info!!!!
Long time breeders of paint horses have always dreaded the birth of an all white foal. These foals will usually die after hours of painful colic. Since these foals do not develop nerve cells in the lower part of their gastrointestinal tract, they are unable to pass their meconium, the foals first feces. Lethal white foals are usually produced when an overo mare is crossed with an overo stallion. Overo paints have been defined as horses where the white marking starts under the belly and moves up, they often have white faces. Tobiano is the other type of paint horse that is described as having white starting over the back and moving down with white legs. These two types of paints are genetically unrelated, so the lethal white syndrome is a genetic disease linked only to the overo.
Owners of overo mares should be aware of the symptoms these foals will exhibit. Besides being all white, the foals often have blue eyes and clear hooves. They nurse and appear normal for the first few hours. At about 5 hours after birth they may start to show signs of colic such as looking at their flank, straining to urinate and rolling. They develop pain because they cannot pass their feces. No treatment has been found and the most humane course of action is to euthanize the foal as soon as possible.
The encouraging news is that the gene that causes lethal white syndrome has been found. So now genetic testing can be done to identify carriers of this gene. The easiest way to prevent this disease while still breeding for overo horses is to cross an overo with a solid or tobiano horse. This makes the lethal white syndrome extremely rare and gives about a 50% chance of producing an overo.
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