Breeding Blues: Downstream, someone asked about the cryptic merle, and I explained it. This leads me to expound a bit more. I breed blue merles because I like the color and shading variations. Fell in love with it in Aussies well before they were an AKC breed, decades before I owned Cardigans or bred them. So when I got into Cardis, I knew I wanted a blue, and, eventually I began to breed them. Well, that means homework. In Cardigans, only the blue merle is allowed, though there are merles of other colors allowed in other breeds. But I breed Cardigans, so when I refer to a blue, I mean the allowed CARDIGAN merle, the marbled white/gray/black. The merle gene is a color modifier. It changes--modifies--a solid black coat. I use the image of a light switch: if that light switch is left on for a long time, you get a heavily merled dog who usually, though not always, has one or two blue eyes, or eyes that are mixed brown and blue. Now and again that light switch isnt flipped on for long at all, and you end up with a cryptic merle, a merle who is predominantly black (with white flashings) with little to no merling. The eyes may be blue, brown, or mixed. There are two types of merles. Heterozygous, or homozygous. Hetero means one merle parent and one black (tri) parent. Homozygous means both parents were merles. For the sake of simplicity, I will use the more common referent for homozygous: the double merle. There is a misconception that the merle gene causes physical abnormalities. This is untrue when one parent is blue and the other black. There is no higher risk of health problems in normal merles than in any other color of Cardigan save one--and that is the double merle. The double merle is predominantly white throughout its body. There may be blue patches, but the dog is significantly white. This frequently results in deafness, though other abnormalities in vision and heart may also be involved. (Not always; there are deaf but otherwise completely healthy double merles in the world.) If a merle to merle breeding is done, there is a 1 in 4 chance of each puppy being a double merle. (A normally marked merle puppy born to two merle parents is NOT a double merle.) Because merle to merle breedings result in a high percentage of mostly white, deaf puppies, the CWCCA Code of Ethics does not allow these breedings, but limits the breeding of blues to blacks (with or without tan or brindle points.) In 2009, it was announced that a test for the merle gene had been discovered. This meant that blue breeders could test all their black puppies to see if any might actually be cryptic merles, so an inadvertent blue to cryptic merle breeding could be avoided. Unfortunately, it was also announced that the merle gene, period, was defective, and it was implied that breeders should cease breeding merles altogether. As it turned out, the genetic information was incorrect. It wasnt the merle gene researchers had discovered, but the gene governing *piebald* dogs. Piebalds are predominantly white with occasional patches of other colors, and the piebald gene *is* linked to health abnormalities. The so-called merle test was immediately rendered invalid. Today, there is NO test for the merle gene, and NO scientific proof that the merle gene carries any higher risk of health abnormalities. It is ONLY when a merle is bred to another merle that health abnormalities become an issue. It goes without saying that there are always health risks when any breeding is done, quite apart from color-linked issues. Gestation is only 9 weeks, and all sorts of things can go wrong. But merle is a health issue only when merle-to-merle breedings are done. I bring this up at length only because misconceptions about the merle gene remain even among vets and other professionals. While the discovery of the merle gene and the resultant so-called test for it were well-publicized, the invalidation of the research and test were hardly mentioned anywhere. And as a blue merle breeder, I feel its important that people know that those who elect to breed blues are not breeding dogs with defective genes, and that if you wish to buy a blue, you are not running a heightened risk of abnormalities.
Posted on: Fri, 25 Jul 2014 16:04:33 +0000
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