Breeding Carriers

[Silverblue]

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.

[Christina]

I don't think VCA allows this but even if it did

Why would anyone be so stupid ?

A carrier can be mated to an A clear dog so can stay in the breeding pool & be bred safely.

The affected pups would have to be PTS from such a mating as posted.

Deliberate cruelty for the sake of keeping a line IMO.

[Darkrai]

nope

[Dogsfevr]

Wouldnt do it irrespective of the new laws UNLESS it was a test mating where the outcome would benefit the future.

I now plenty of breeders who have done such matings in conjunction with the uni or similiar to get test markers & the likes understood.

[lappiemum]

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.

PRA is in my breed. I would not do it.

Edited to note that we can genetically test for the PRA that is in our breed, so its relatively easy to know which lines are clear and which are carriers.

Edited March 20, 2010 by lappiemum

[lappiemum]

Should add that the Code of Heritable Diseases says that carrier to clear matings should be tested for PRA status.

However, not all breeders will do this.

edit to note that the Code is Vic legislation, and as such only affects Vic breeders. Breeders in other states would have to look to see if there is legislation there that covers this issue.

Edited March 20, 2010 by lappiemum

[Christina]

Should add that the Code of Heritable Diseases says that carrier to clear matings should be tested for PRA status.

However, not all breeders will do this.

Correct me please if I am wrong

I thought if you do a carrier to clear mating & wish to breed from a puppy resulting from this mating

The puppy would be an A clear or B carrier.

Therefore as long as the pup, when adult, is bred to an A clear dog there is no need to test.

You already know resulting pups will be 50% A & 50% B but none C affected.

Obviously if wanting to breed to a B carrier dog the test for PRA would have to be done. To ensure the dog is an A clear.

I have desexed all pups from an A to B mating in the past so does the new code mean that if I did the mating again any desexed pups would have to be tested anyway ?

[lappiemum]

The word is should, but here is what it actually says (emphasis added):

Clear x Carrier **50 % Clear, 50 % Carrier

1. Progeny to be used for breeding purposes should be tested for the heritable defect**.

2. All progeny should be tested for the heritable defect

3. Carrier animals should be de-sexed if not to be used for breeding purposes.

**Testing is required as in practice the unpredictable nature of the process of gene inheritance in these combinations may cause the actual % outcomes per generation to vary from the theoretical outcomes.

# An Approved Breeding Program is one that has been adopted and endorsed by the relevant VCA associated breed club.

[lappiemum]

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.

[Christina]

The word is should, but here is what it actually says (emphasis added):

Clear x Carrier **50 % Clear, 50 % Carrier

**Testing is required as in practice the unpredictable nature of the process of gene inheritance in these combinations may cause the actual % outcomes per generation to vary from the theoretical outcomes.

The ** is interesting. I thought it was 50-50 for sure

So is the reality that a clear to carrier mating may produce say 25 % carrier + 75 % clear ?

[lappiemum]

The word is should, but here is what it actually says (emphasis added):

Clear x Carrier **50 % Clear, 50 % Carrier

**Testing is required as in practice the unpredictable nature of the process of gene inheritance in these combinations may cause the actual % outcomes per generation to vary from the theoretical outcomes.

The ** is interesting. I thought it was 50-50 for sure

So is the reality that a clear to carrier mating may produce say 25 % carrier + 75 % clear ?

Yes, the 50/50 is definately only statistical likelihood. It can (and does) vary.

[whippets]

I wouldn't do the breeding in the first place. You already know that it's a roll of a dice.

You may get all carriers, you may get some with it and some carriers and if the dice roll was really bad you could get all pups with it. It's the dogs that exhibit the disease that would end up paying the price for someones curiosity.

There is enough known about PRA to not even bother with markers/test matings.

[armahani]

The ** is interesting. I thought it was 50-50 for sure

So is the reality that a clear to carrier mating may produce say 25 % carrier + 75 % clear ?

Everyone seems to get completely confused by this. The odds with a clear to carrier mating is NOT that 50% of pups will be clear and 50% of pups will be carriers in an average size litter. This is an incorrect way of describing the odds, and just leads people to have an expectation that is very rarely met.

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.

Does that make sense? Same as tossing a coin. Each time you do a coin toss, you have a 50% chance of getting heads and a 50% chance of getting tails. That does not mean, however, that if you tossed the coin 8 times (as an illustration of 8 puppies) you would get 4 heads and 4 tails . You could end up with 8 tails and 0 heads, 7 tails and 1 heads, 6 tails and 2 heads, etc etc, through to all of the possible combinations.

I know the common (easy to understand) explanation given is that you will get 50% carriers and 50% clears with a carrier x clear mating. But that would be only the case if your sample was hundreds of puppies. Given most litters are far smaller than that (thank goodness!) it will very rarely turn out exactly 50/50. Instead think of it as each pup has an equal chance of being either .... but the combination you will get in the litter may vary considerably.

Edited to add that carrier x carrier matings can only be done in Victoria under an approved breeding program - so no doubt if there were particular reasons that a breed club had decided to allow such matings, I imagine there would need to be guidelines give on when and why it could be done and what protocols should be followed re affected pups. Not sure which breeds (if any) this applies to. But might be worth while checking with the breed club of the breed you are curious about.

Edited March 20, 2010 by armahani

[Bilbo Baggins]

Each pup has 1 in four chance of being clear and a 2 in four chance of being a carrier and 1 in 4 chance of having PRA.

It does not work on the whole litter its the individual pup.

At the end of the day you could extrapolate a litter figure.

[Sandra777]

No matter where I lived I wouldn't be mating a carrier to a carrier.

[oakway]

You'd need your head read if you did a stupid thing like that.

[becks]

Nope, wouldn't knowingly mate a carrier with another carrier.

[Jed]

If the dog is a carrier, I would only mate to a clear. That will give you clear and carrier.

The only way, as I understand it, to get affected, is to mate carrrier x carrier, which I would not do.

If I particularly wanted to retain the lines, I would mate the carrier to a clear dog of the type and bloodline I wanted, and hope that a suitable pup would be clear. Then I would mate that clear pup to the carrier I wanted to use.

I am not sure of the ins and outs of the law in Vic, but if you test the pups which you may keep, I think you can sell the other carriers as pets, to be neutered and not bred from, if you notify the new owners that the pup may be carrier, and explain what that is.

If I did a mating which gave me affected pups, I would pts. However, I think there are sufficient nice dogs in Vic that you should not have to do this.

In the past, with serious hereditary problems, before DNA t ests, breeders did do first generation matings to try to ascertain whether the dog was a carrier or not. I believe you need about 49 pups to be sure the dog is not carrying the gene.

[Bob]

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,

[Silverblue]

No matter where I lived I wouldn't be mating a carrier to a carrier.

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.

I am aware that "Most" breeders in other states wouldn't do it, but surely there are some out there that aren't as scrupulous as others and would do this mating.