Breeding Carriers

[Kustali]

We can test for dominant PRA in the Mastiffs, although apparently it's not common in the dogs in Oz and no one else really tests for it, mine are imports so i did it anyway to be sure they were not affected with it. Both are clear. It's one of the few tests we can DNA test for (along with the fluff gene, not affecting health) so it is a sure thing...you know what they are and you know the offspring will be clear.

Why would anyone knowingly breed to produce affected dogs....beats me. I tested to make sure i wasn't going to produce dogs that would be blind!

[Bilbo Baggins]

My understanding was that any breeding capable of producing affected pups, ie, carrier/carrier were not permitted under the code. That is the case for Bedlingtons and CT anyway.

In regards to carrier to clear matings I am aware of one that produced eight pups, all clear, a very unlikely result. Obviously, that also means that a mating can produce all affected dogs.

Colour wise I mated a blue (dominant carries gene for liver) with a liver dog expecting a mix of blue and liver pups. I got one blue out of seven.

Regards,

Bob that what I was getting at with my post. I was looking at the GT Website today and they where quoting the 50% 25% ratios.

Its 2 out of 4 carrier, 1 out of 4 clear and 1 out of 4 affected per each egg and sperm. So above result is entirely possible.

[armahani]

My understanding was that any breeding capable of producing affected pups, ie, carrier/carrier were not permitted under the code. That is the case for Bedlingtons and CT anyway.

Under the code these breedings are allowed (if you are talking GPRA - which is recessive) if under the auspices of an approved breeding program for that particular breed. Words from the code are:

1. Breeding is not recommended. Must only occur as part of an approved breeding program.

2. All progeny must be tested for the heritable defect.

3. A diseased (Affected) animal must not be disposed of to another person without advice of the animal’s heritable defect status

4. Affected progeny (or any juvenile off spring confirmed as ‘Affected’ on test) should be de-sexed unless they are to be used in an approved breeding program, must not be permitted by their owner to suffer from their condition if it develops and should be under the supervision, advice and monitoring of a veterinary practitioner.

In regards to carrier to clear matings I am aware of one that produced eight pups, all clear, a very unlikely result.

Unlikely but possible

Obviously, that also means that a mating can produce all affected dogs.

No - not possible. Not from a carrier x clear mating for the recessive form of PRA. You could have all carriers though - but no affecteds.

That is sort of what I am getting at, why is it only "Prohibited" In Victoria, shouldn't the ban be Australia wide if the consequences are so bad.

Because animal cruelty legislation (which is where the "prohibition" comes from) is State based law. For is to be the same situation elsewhere, other States would have had to have passed similar laws and codes of practice as in Victoria.

Why would anyone knowingly breed to produce affected dogs....beats me. I tested to make sure i wasn't going to produce dogs that would be blind!

I think the main time you will find breeders "knowingly" breeding affected dogs of any condition, is where tests reveal that the incidence rate of carriers and affected animals in that particular breed is so high (hardly any "clears"), that the only way of not completely depleting the gene pool, "breeding into a corner" and possibly losing the breed from existence is to do those sorts of breedings. Not a decision I would want to be faced with, and I know many people would just stop breeding if they were faced with those sorts of decisions. But this is why "approved breeding programs" established by breed clubs may allow these sorts of breedings in certain circumstances - if they feel there is no other way for the breed to continue successfully with a viable sized gene pool.

[mikelli]

I know of a clear to carrier mating that produced 100% carriers, tough result, but none the less you cannot assume anything when it comes to the way the genes fall!!!

[Bob]

Apologies to all.

In regards to a clear to carrier mating I stated "Obviously, that also means that a mating can produce all affected dogs".

I had meant to put this in another para and state "carrier/carrier" mating.

I also stated that I was aware of a carrier clear mating that produced 8 clear pups, an unlikely result. Yes, it was an unlikely result but verified through DNA testing. And no, it was not a mating I did.

Sorry,

[angelsun]

My understanding was that any breeding capable of producing affected pups, ie, carrier/carrier were not permitted under the code. That is the case for Bedlingtons and CT anyway.

In regards to carrier to clear matings I am aware of one that produced eight pups, all clear, a very unlikely result. Obviously, that also means that a mating can produce all affected dogs.

Colour wise I mated a blue (dominant carries gene for liver) with a liver dog expecting a mix of blue and liver pups. I got one blue out of seven.

Regards,

Bob that what I was getting at with my post. I was looking at the GT Website today and they where quoting the 50% 25% ratios.

Its 2 out of 4 carrier, 1 out of 4 clear and 1 out of 4 affected per each egg and sperm. So above result is entirely possible.

We have VWD in my breed so we run into this sort of thing all the time. What was mentioned for clear to carrier:

The odds are that for each individual puppy, they EACH have a 50% chance of being clear and a 50% chance of being a carrier.

applies for carrier to carrier as well. Because each parent has one clear marker and one carrier, each puppy of a carrier to carrier mating has a chance to be clear (taking that one clear from each parent), it also has the chance of taking a clear and a carrier marker to become a carrier, and then the chance of taking a carrier marker from each parent to become affected.

It's not about the total numbers in the litter as that will vary. These figures apply to each individual pup within the litter. I have a friend that did (before the DNA test to conclusively determine carriers with vWD) a carrier to carrier, and although the odds seem to read that there is a 25% chance of getting a clear from this, she got of five pups, three carriers and two affected. The odds certainly were against her in that litter.

Regardless of the state, or the regulations set in place, I do not beleive there is just cause for doing a carrier/carrier breeding regardless of the health issue discussed.

Would people that did not have to worry about the legislation, give this a second thought? Or is it simply because 'big brother' is watching, would they change their breeding plans?

[Steve]

Just a hypothetical, I am after opinions,

Say you lived in Vic would you mate a carrier to carrier (PRA) knowing you would have to test the whole litter,

And if you did what would you do with the Affected pups ??

Just curious.

In the Introduction to the Code of Practice for the Responsible Breeding of Animals with Heritable Defect that Cause Disease (2009), the Department of Primary Industries (Vic) notes that:

Breeding programs must consider the effects and ethics of high risk mating combinations that may, based on the principles of genetic inheritance, in theory produce animals with heritable disease. Where such heritable disease has potential to cause severe welfare issues for affected progeny such breeding programs must be justifiable. Affected progeny must be assessed and humanely destroyed if they suffer. Such animals must not be used for breeding.

The purpose of the Code is to set standards for the prevention and spread of heritable defects and the expression of disease caused by them. The Code aims to educate animal breeders how to best minimize or avoid the development of heritable disease in progeny caused by inappropriate selection and mating of animals with heritable (genetic) defects. It also outlines breeding practices that will assist the reduction of the prevalence of the heritable defect in the animal population.

The standards set by the Code should be practiced by owners and custodians of animals used for breeding that are affected by any heritable defect that causes disease and must be observed for breeding of animals with heritable (genetic) defects causing the diseases listed the Schedule of the Act.

A person breeding animals in a program that conforms at least to the principles in this code is not considered to be breeding animals recklessly or intentionally as defined as an offence in Section 15C(1) of the prevention of Cruelty to Animals Act 1986.

It should be noted that the legislation is Victorian State legislation, and as such only applies to Victorian breeders. Breeders in other states are subject to their own state legislation.

Does this include the 5 diseases which are listed in the legislation which says carriers can not be used for breeding?

[Steve]

Unless you had a really really special reason and got someone to double check you had no choices and tested all resulting pups and were prepared to cull - mating carrier to carrier is not only dumb its negligent.

[Silverblue]

Just to clarify I was not/am not contiplating doing such a mating.

I just shudder to think what might have happened had I not found out that the "Clear" dog that I was lead to believe was the sire of my pups was infact not the father & the real sire has turned out to be a carrier.

I WOULD have done this this mating thinking my bitch was clear by parentage, when now she is a confirmed carrier, wonder what the ramifications would have been then.

[Jed]

I would have no hesitation in using a carrier which was a good dog with a clear bitch, if I could produce the pups I wanted. If the best pup was a carrier, I would have no hesitation in keeping it, and finding a suitable clear dog to mate it with.

There are some very nice dogs around which are under utilized because they are carriers. I can't see a problem with carriers being used in breeding programs, because we can identify them, and there is no chance of producing affected - unless we deliberately set out to do that.

And I wonder that anyone would be that stupid? Quite apart from the legislation.

I wonder sometimes if breeders do thoroughly understand the mode of inheritance of some of these problems in their breeds, and are frightened of using carriers because of misunderstanding?

[armahani]

Just to clarify I was not/am not contiplating doing such a mating.

I just shudder to think what might have happened had I not found out that the "Clear" dog that I was lead to believe was the sire of my pups was infact not the father & the real sire has turned out to be a carrier.

I WOULD have done this this mating thinking my bitch was clear by parentage, when now she is a confirmed carrier, wonder what the ramifications would have been then.

See I'm just paranoid. This is why I parentage test all of my litters, and all my "clear by parentage" litters are certified as such - so they have that status as a tested status, not just because I say that's what they are . I also prefer not to do a carrier x clear by parentage litter - would prefer always to have the second dog actually tested clear. But as I said - I'm paranoid - perhaps it's overkill