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[RC] More on overos - Lynn WhiteTitle: More on overosI’m not a equine color geneticist by any means, but I have read a couple books and talked to breeders. The whole horse color “language” seems to be regional and meanings change with respect to where one is from. It’s kind of a colloquial thing. To the layman, the term overo can refer to any spotted horse in some areas. When one is talking to an equine geneticist, the three terms of spotted horses (sabino, tobiano, overo) refer to actual genetic makeup. The three types of patterns have three types of genes that can be identified. As stated in a previous post the horse described is most likely a sabino. Many people have sabino horses and don’t even know it…but the tell-tail sabino markings are a white spot on the belly, high leg markings, and a white skinned lower lip. The sabino gene occurs in just about every breed. The overo or tobiano genes on the other hand do not occur in purebred Arabians or any of the other desert breeds. Someone might have a pintabian with the tobiano or overo gene, but this only means that some ancestor of that horse was a paint or pinto of some other breed. So one would ask (like my husband) why is color genetics so important? The answer lies with what is “fashionable” (i.e., what will sell) at the time, but more importantly there are color genetic combinations that are lethal. There is the lethal roan and the lethal white. You get the lethal white when you mate two heterozygous overos together and get a homozygous overo (25% probability). The lethal white foal comes with the nasty trait of not having the ability to digest food. So foals are born alive and PURE white but die within a couple days…not a damn thing one can do about it. This is why if you want to breed your colored mare to another colored stallion you really need to know who carries what genes before you do anything. I personally know two backyard breeders who were unaware of this and ended up with pure white foals that died within two days of birth. The breeders just did not know anything about lethal white, and didn’t ask their vets or pick up a book. I know I’ve strayed from the original post, but I live in “Paint Country” and look at a lot of colored/spotted horses trying to figure out what the heck they are. My color preference is anything with the crème dilution…buckskins in particular. I also like grullas, but one would be hard pressed to find a grulla that is more than 75% Arabian…I think I’ve only seen one grulla on the endurance trail, and that was a mustang. Only 4% of registered QH’s are grulla. It’s not a common color. Here’s a pretty informative website: http://www.animalgenetics.us/LWO.htm Happy looking, -Lynn
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