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Blue Merle breeding/genetics question

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I have an 11 month old female, Wren, pure bred border collie.  What a great dog - smart as a whip, super friendly, very very sensitive/responsive, and showing herding inclinations.   She has the classic border collie look - black and white, brown eyes and longish hair.  I'm not getting her spayed for the time being because I want to explore the possibility of breeding her down the road.  

However, a few months after a brought her home, it came to light that both of her sire's parents were out of dogs with the blue merle gene.  At least one of them was not showing, otherwise i don't think they would have been bred together.  Her sire is on the big side - ~50 lbs - red and white, longish hair and brown eyes and healthy at nearly 3 years old.  In Wren's litter  (7 puppies), there where no puppies with the blue merle coloring - they all were black/white, black/red, or tri-color.  There was one that was mostly white who ended being deaf.  So my question is: should Wren be bred? Is she a "carrier" for health problems or could she develop health problems down the road?  

Thank you for any insight,


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Just to clarify, Wren's sire did not show any merle markings?  Was Wren's dam a merle?

There are no "carriers" of the merle mutation in the way usually meant by that term.  If a dog has one copy of the mutant gene, it shows the characteristic pattern.  If it has two copies, it is a double merle (homozygous merle) and is usually mostly white with eye and ear defects.  The only rare exception to this is a "cryptic merle".  This is a dog that shows only a tiny bit of the merle pattern that could be overlooked.

First, Wren is in no danger of developing heath problems later related to the merle mutation.  If she is healthy now, she will never show the defects associated with double merle.

Since you don't see any merle markings on Wren, she almost certainly is  just a "normal" border collie--no problems in breeding her associated with merle.  If she is a very rare cryptic merle, then the only precaution you need to take is to avoid breeding her to another merle.  Post lots of photos of her so we can take a look.  Or better, let an experienced breeder or veterinarian who is very familiar with merle examine her.  This exam would be necessary in any case if you want to breed her.

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There are actually generic color tests now so you could definitively determine if she carries merle. As the poster above noted, merle is dominant, do if she had the gene she should display the pattern, cryptic excepted.

As for breeding, unless you can breed to improve the working border collie, I would suggest not breeding. There are scads of lovely, even tempered, smart border collies out there who add nothing special to the gene pool. If she likes to work stock and proves herself to be an excellent stockdog, then breeding might be worth considering.


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Agree with Julie.

AND get X-rays on her hips to make sure they are scored good or excellent AND send off a sample swab for genetic testing to determine her status for several genetic diseases found in the border collie breed, e.g. CEA, EAOD, TNS, mdr1, etc.

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^^ What they all said.

Just because 2 (hopefully no more than 2) grandparents were merle doesn't mean that offspring of solid colored dogs from that mating would be merle unless the solid-looking merle was that uncommon phantom or cryptic merle or it was bred to a merle.

If your dog is indeed a solid color then she doesn't carry any merle related health issues. In fact, the only health issues associated with merles are in the case of irresponsible merle to merle matings, in which case the homozygous pups will likely have vision and/or hearing problems. There is a slight increase in likelihood of deafness is heterozygous merles, but it's actually somewhat less than for blue eye dogs of any color.

As Julie points out, it would be easy enough to eliminate any questions of her being a phantom merle by genetic testing, which can also rule out the possibility of her passing on other inherited diseases.

As she also points out, breeding decisions should be based on proven excellence in stockwork.

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