I was speaking to a lady I met when I took my dogs for a walk and she said she had mated her dogs - they are half brother and sister! (same mum but different dads).  I was a bit surprised my this.  Is this classed as in-breeding or does the kennel club allow this as they are not true brother and sister?

It is only full brother x sister, mother x son and father x daughter that isn't allowed. Half brother x half sister could technically speaking have 50 % fresh blood and be less inbred that, say, two cousins of similar ancestry. It's more important to look at the big picture and not just the two parents -it all matters.

Even with 50% fresh blood/genes and the Kennel club O.K's it. I still think it is wrong.

Even with 50% fresh blood/genes and the Kennel club O.K's it. I still think it is wrong.
Knowledge of each and every dog involved is far more important than percentages or names on paper. :)

Even with 50% fresh blood/genes and the Kennel club O.K's it. I still think it is wrong.

You could have two 100 % unrelated parents with a large amount of genetic problems causing very sick pups, or two half siblings perfectly healthy giving you healthy pups -it's not black and white. :) Wish it was!

Certainly.  I'm alarmed when I see people write, "I've checked the pedigrees and there are no similar relatives" as though that makes it a good mating...... :(

Probably the best dog I will ever have the opportunity own was the result of a half brother / sister mating - as others have said there is more to working out the impact of a mating on a genetic basis than looking at simple direct relationships.

K

ditto,

My current young champion bitch is the result of half brother sister mating.  Her parents both being out of my first champion bitch, and the sires both being imports from different countries, so as has been said possibly less close than some other matings that seem less so.

Of course I am going right out to unrelated stock when it comes to breed from her.

As I knew the lines of the bitch who was Mum of both parents, and she was a healthy 3rd generation home bred 9 year old (now 10 1/2), whose litter mates I was in touch with and had produced 3 healthy quality litters and had healthy quality grandchildren, I felt able to do so in order to retain the type I wanted with both the parents being outcross breeding on imported bloodlines.

If line breeding you do have to think hard what you hope to achieve and where you are going to go next.

Generally I wouldn't in my breed go closer than half uncle to niece, in other words mate a bitch to a half brother of her sire/dam.

What people don't realise is that, theoretically, same-litter siblings can be totally unrelated genetically. Statistically unlikely, but theoretically possible. Here's how.

Very simplified, let's call sire's genes A, B, C, D, E and F, and dam's genes 1, 2, 3, 4, 5 and 6. Each sperm and each egg contains a random half of the relevant parent's genes. So the sperm containing genes A, B and C could fertilise egg containing genes 1, 2 and 3, creating puppy ABC123. With me so far? Now the sperm containg genes D, E and F fertilises egg 4, 5, and 6, creating puppy DEF456. It's immediately obvious that these two puppies, although having identical parents, have no common genes whatsoever.

That makes perfect sense Jean...thank you :) I'd never really thought about it like that!

Certainly.  I'm alarmed when I see people write, "I've checked the pedigrees and there are no similar relatives"

Can I ask why you are alarmed?

>Can I ask why you are alarmed?

Because it suggests that think that unrelated dogs = healthy puppies. They're only looking at the names, and know nothing about what the dogs were actually like.

Whilst I appreciate that with knowledge and care this sort of mating should not necessarily lead to problems, I think it is totally unnecessary in a breed like labradors which such a large gene pool.

Whilst I appreciate that with knowledge and care this sort of mating should not necessarily lead to problems, I think it is totally unnecessary in a breed like labradors which such a large gene pool.

> What people don't realise is that, theoretically, same-litter siblings can be totally unrelated genetically. Statistically unlikely, but theoretically possible. Here's how.

I wish it were that simple, jean!
Genes come in pairs, like shoes. Every puppy gets 50% of its genes from dad, and 50% of its genes from mum. But there are many many pairs involved. Mostly it will get a red shoe from dad and a blue shoe from mum, on every single level. But sometimes they'll get a yellow shoe from both that makes a pair (when recessives meet up). It is not as simple as saying Xmeets Y in one puppy and Z meets Q in another - that doesn't work. Very sorry but there's no real way any sibling can be that genetically unrelated to its brother or sister.... too many genes involved!!! Thousands, millions.... siblings are always very closely related. The laws of assortment might mean on ONE gene level some inherit, some don't, but so many other genes are involved (millions) it is impossible for them not to have loads in common.

>I wish it were that simple, jean!

That's why I said theoretically, not realistically. Obviously they will have the common genes that make them a dog and not a horse or a fish, and they will have the genes that contain the particular 'type' of the breed, but highly qualified geneticists have agreed that theoretically it's possible for two siblings to be less closely related than two third cousins twice removed. It's very important to remember that siblings are not clones.

I am quite prepared to admit that I don't have the knowledge that many of you have and I'm not suggesting that it is necessarily due to line breeding but why have some breeds of dog become so exagerated and unhealthy. For instance, no not all, but far too many of the breed I love 'Bassets' suffer from so many problems. Could someone explain to me how this has come about if not through breeding?

Partly the difference is that a dog of a particular breed is identified as such, whereas mongrels or crossbreeds aren't, and so their health problems go largely unreported. Trust me, mongrels can suffer any of the problems that pedigrees can!

> Could someone explain to me how this has come about if not through breeding?

Everything comes about through breeding but a trait can be introduced by total outcrossing too.

In Bassetts for example, say a very exagerated dog is imported from another country and is a total outcross, mated to your bitch he will pass on many of his exagerations but the resultant litter will have a very low COI (coeffecient of Inbreeding).
Repeatedly choosing for a trait regardless of the inbreeding causes exagerations too.

Exaggerations are bred in by selectively breeding for them.  To be fair, not all exaggerations cause health problems, but they are exaggerations none the less and is really as a result of fashion and the way the breed standard is interpreted and what is being judged in the ring. 

Hi i posted the same question regarding line breeding and got about 60 useful responses this was a few weeks ago in the breeding section