Many collie type breeds carry a genetic mutation that makes them sensitive to certain drugs. MDR1 tests for this gene. The test comes back as Normal/Normal, (N/N) meaning there is no defective gene, and the dog will not be sensitive; Mutant/Normal (M/N) which means the dog will be a carrier and may be mildly sensitive; and Mutant/Mutant,(M/M) which means the dog carries both copies of the gene and will be sensitive to the drugs such as Ivermectin. There are alternatives to all the drugs the dog may be sensitive to, but the vet will need to know that the dog is M/M.

The test is not widely used in the UK, and as a result there could be many M/M dogs around that we don't know about. Vets usually avoid the drugs known to cause sensitivities in collie types, just in case. A M/M dog is fine in every other way and will need a completely normal life.

Sooooo - would you ever breed a M/N to a M/N dog? The likelihood is they will produce 25% M/M pups. Is it a huge deal, if the dogs are fantastic specimens in every other way? There seems to be a big split of opinion of this - some breeders think it is a defect and therefore should be bred out; others think if we only breed from N/N dogs we will miss out on the other qualities the dog may have. The MDR1 gene could be linked to temperament, herding ability, anything - we just don't know.

Thoughts?

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Under normal circumstances, I would say (if I am reading this right and this is a recessive gene) - I would mate M/M to N/N - or M/N to N/N - but no, I wouldn't bring two carriers together - but then, that's relatively easy to say in a numerically large breed.

If you are talking about your breed, or an equally numerically small breed, then I don't know - I would like to think I wouldn't - but then, if you already have a tight gene pool, I don't honestly know

I am guessing M/N would produce 50% clear, 25% carrier, 25% affected statistically?

For many conditions, we know there is a big difference between genetically affected and clinically affected - some dogs can remain asyomptomatic their entire lives - I guess knowing exactly how clinically affected dogs were, and how they suffered would considerably affect my decision. - I would like to believe in an ideal world, I would never breed a pup affected for any condition, sadly, I know life isn't like that because there are conditions we can only "do our best" with.

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I agree, in a statistically large number of specimens there is far more choice and mating clear to clear is possible. If the number of the breed is low however it's a difficult decision. Not being faced with that decision it's easier for me to say I'd probably opt for the best progeny possible whilst also going for damage control.



There is a range of drugs which affect MR1 M/N carriers and M/M affected dogs.

Drugs reported to cause problems in dogs that carry the MDR1 mutation. Information from the VCPL at Washington State University.

I don't know if there are equally good alternatives in every case but if a parasite becomes highly resistant to a drug that is problematic for treatment and preventative medecine.

You can endorse the papers /advise a puppy buyer not to breed or to spay/neuter and prevent an accidental mating to happen but unfortunately some people will just ignore that information and they aren't the ones likely to worry too much about the health status of the sire and of course mismatings do happen too and not everyone agrees with terminating a pregnancy or they may not discover their problem until it is too late.

So I suppose if you cannot find an excellent sire to produce clears of good breed type and produce a carrier or an affected dog, well I wouldn't like to find out that someone who had seemed ok bought and then bred a pup from me irresponsibly even if it's not my fault that some people do.

I wouldn't like to bottleneck the gene pool either but if you breed to keep one pup for yourself the remainder of the litter would go to working/show/ or pet homes and health and temperament are I think more important for a pet dog buyer than a strong herding instinct that would never be used in a pet home.

Some would say 'don't buy a herding dog if you won't use it that way' but they are often very good trick and sports and obedience dogs and live happy fulfilled lives when channelled in those directions by equally energetic and sociable people. What if MDR1 is linked to something desirable? Well, nobody knows that it isn't linked but there's no evidence that MDR1 clear dogs lack in temperament or herding instinct which you might expect if they were linked genes?

It is for my breed that I am thinking about. There is only ONE stud here in UK (and his progeny), that is MDR1 N/N. He happens to be mine. There are only 36 ES altogether in the country. As this stud is already father to 31 pups, it would be best to use the other stud. However the other srud is MDR1 M/N. That is no problem when breeding to bitch puppies of mine, as they are all MDR1 N/N. But I have another bitch (unrelated to either stud) who is M/N. When I saw the M/N stud (before he was tested), I thought he would be perfect for this bitch, they have no faults the same, good lines, he has great hips, fab temperament, just what I would have wanted. However now I know they are both M/N, I ruled out this pairing. Then I got emails from people saying they would never rule out a mating based on MDR1 status, so I started wondering. And I'm still wondering lol.

ETA: they are not just a herding breed, in fact mine don't herd. They are a fantastic pet. I just used that as an example, which someone had given me.

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Breed for a useful dog and you often get a beautiful, useful dog... breed only for a beautiful dog and you are on your own in the useful department.

Tricky one. I wouldn't like to see a double M/N pairing, but with such a tiny gene pool there's not much in the way of options. Could you not import sperm from another stud?
If you do decide to use this dog, you can test the puppies and put endorsements on that are appropriate to each puppy's status.

Saw one of yours at the recent Wilmslow agility show.

Mating clear to clear is possible, but carrier / affected to clear should not be ruled out even in the largest gene pools - all you need is something 'new' to appear on the horizon and you could get all sorts of bottlenecks where you least expect it.

Some DNA tests show up around 40% of a gene pool as being carriers - so if you ruled out all the dogs carriers for one or both - you would probably lose 60% of your gene pool in an instant - no breed could sustain that.

In my own breed - we are now 3/4 or even more generations down with PRA testing and it's been done responsibly and not losing any worthy dogs, so now many litters are clear by parentage - similarly we are probably 2 to 3 generations down with CNM (affected dogs don't live) so CNM is carrier or clear - but we are now starting to see Clear by Parentage litters coming through - my next generation will be my first CNM CBP.

However, that is immaterial in this scenario - OP - I think if you feel the dogs are a good fit and it's going to benefit the breed and the gene pool, then you have to go for it and just be clear what the implications would be (I assume you would test the litter before leaving?)

Don't forget also in these situations, we are talking statistically usually over x number of litters - so your litter could be all clear, all carrier or all affected - although of course more then likely to sit somewhere befween all three - although you do have to think where you go next if you do produce an all affected litter.

It's not a genetic condition - but same principle - two of my litters have been black / chocolate - my first litter I had a straight 50/50 black chocolate (2 girls and 2 boys of each) - my last litter was heavily chocolate which defied the odds really as dad was black carrying yellow and chocolate.

I also know of a litter where the sire was black carrying yellow and chocolate and the bitch chocolate carrying yellow - ALL the pups were yellow - statistically, two pups out of 8 should have been yellow, one with liver pigment, but the whole litter were yellow with black pigment - we never know what surprises Mother Nature is going to spin us

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We have frozen sperm here, and it has been used once but was unsuccessful. He's a S/W with a brindling gene. Not the colour I'm after. Its such a difficult decision to make.

Was it Tilly? How was she?

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Breed for a useful dog and you often get a beautiful, useful dog... breed only for a beautiful dog and you are on your own in the useful department.

I'm scared to be honest! I really do think these two are a great fit but I don't want to be the breeder who brought lots of affected pups into the UK ES world. Yes of course if I did go ahead I would definitely test all the pups. Still not sure. I'm thinking more and more that I need to import another male..........

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Check out my English Shepherds
http://www.edenvillage.co.uk

Breed for a useful dog and you often get a beautiful, useful dog... breed only for a beautiful dog and you are on your own in the useful department.

tough one for you as your breed is very rare. i have enclosed an article by our breed council for anyone thats interested in MDR1 .There are a few rc kennels that do test for it but not many as vets are more clued up now on its side effects for the breed.
Drug Sensitivity

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See thats another thing - most people don't test for it, and there could be many MDR1 M/M dogs around. But once you do, and you know..........

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Check out my English Shepherds
http://www.edenvillage.co.uk

Breed for a useful dog and you often get a beautiful, useful dog... breed only for a beautiful dog and you are on your own in the useful department.