How close is too close (Inbreeding.)

[ReadySaltedPeanuts]

Noticed in another thread someone commented about the inbreeding in the pedigree of a horse.

So just a general musing, how close is too close?

I know in icelandic horses there is a very common and succesful stallion (Not sure if he is still alive, but is in many pedigrees.) that is completly inbred:

Ófeigur frá Flugumýri

]

His sire and dam are full siblings, would you consider this wrong?

http://www.allbreedpedigree.com/ind...A+FLUGUMYRI&g=5&cellpadding=0&small_font=1&l=

 

[AmyMay]

There's a very interesting thread going in Dogs at the moment. Well worth reading.

 

[ridefast]

Welsh ponies and cobs seem to be very inbred too. I've heard said that line breeding for one generation is ok but not for 2. I don't know but I would have thought it's probably not good long term.

 

[Nightmare before Christmas]

I was told by a stud, parents are a no, grandparents are fine.

 

[pip6]

I asked a top Arab breeder about this (half bother/sister combinations common). He said if they are very top quality with no issues no problem if closely related.

 

[s4sugar]

In this instance where the siblings parents had no common ancestors and the horses were excellent then it was probably a good thing especially if it meant keeping a line clear of prevelent animals.
It is too easy in a numerically small breed to end up with all the stock closely related and nothing to turn to. Keeping seperate strains gives more options in the future.

That said it is too close for most cases.

 

[ReadySaltedPeanuts]

But would you breed two full siblings together? Like in Ofiegurs case?

 

[s4sugar]

If they were the only pair remaining that did not have a particular ancestor and were both excellent from superb parents -yes. Otherwise probably not.

 

[AMW]

there is an old saying ' line breeding if it works, inbreeding if it doesnt'

full brother & sister to me is a nono

 

[RealityCheck]

Unless a breed or particular gene is exceptionally rare, don't do it. My former stallion has one common ancestor (4th gen sire side, 5th gen dam side) because the cream gene in his breed is rare in quality stallions.

At that distance I think it's okay, but you wouldn't do the nasty with a your brother or cousin for well document health reasons, so would you risk an already risky and complex breeding operation by inbreeding to such a degree?

I've seen mares I like and would consider adding to my breeding programme, but when you look pedigrees with 30%+ inbreeding over the first 6 gens the mind boggles...

 

[Gloi]

One generation of close breeding wouldn't bother me so long as there is new blood coming in after that.

 

[LittleBlackMule]

RSP - that Icelandic stallion you posted as an example, have you looked closely at the rest of his pedigree?
Not only are his parents full siblings, but also his grandparents, great grandparents, and the rest! That cannot possibly be healthy long term, even if they've got away with it so far.

 

[LittleBlackMule]

The only experience I have of inbred horses (or line bred as the breeders prefer to say) is with Welsh A's and C's. The first thing to be affected was the mind of the pony, so you ended up with a stunning looking example of the breed, but with temperament 'glitches'.

 

[Gloi]

RSP - that Icelandic stallion you posted as an example, have you looked closely at the rest of his pedigree?
Not only are his parents full siblings, but also his grandparents, great grandparents, and the rest! That cannot possibly be healthy long term, even if they've got away with it so far.

How do you expect the grandparents etc. not to be related when the parents are? There doesn't seem to be any inbreeding in generations before the parents.

 

[RutlandH2O]

There's an old saying that posits a formula for breeding:

"Let the sire of the sire be the grandsire of the dam on the dam's side."

I learned this little saying when I was active in the dog fancy. The fact that so many terms in dogs are taken from horses, I would think this saying refers to line-breeding of an equine nature. Of course, breeding formulae are interesting on paper. Any blueprint for living, breathing animals is fraught with the realities of genetics.

OP, I wouldn't breed full siblings ordinarily. However, if their sire and dam were themselves unequivocally outcrossed, and there were mitigating circumstances for a breeding of brother/sister, I might consider it, only if there were stringent protocols in place as to future breedings of the offspring, i.e. outcrossing to another line.

It must also be remembered that continued inbreeding can lead to reduced size, among many other things. If there are unexpressed genetic anomalies in a given pair of breeding animals, doubling up should express the fault. Outcrossing simply reduces the probability of a fault being revealed. Inbreeding doesn't cause genetic problems, it just manifests what is already there. Many years ago, I heard of a dog breeder who contemplated undertaking intense inbreeding in an attempt to expose any genetic faults in her line of dogs. She intended to spay/neuter all progeny and follow them to maturity. I never found out if she ultimately went ahead with her project.

 

[Dry Rot]

Inbreeding is perfectly OK provided the offspring are 100% perfect in every way!

The problem is, you won't know that until you've bred -- and even then your super-dooper foal may be a one off by sheer luck with every other bred the same way a total dud.

The great farm livestock improvers never revealed their pedigrees and I suspect there are more lies in the published pedigrees than are ever told in court. DNA testing has revealed what many would have liked to have remained hidden!

Line breeding is something that needs to be done over many generations with very harsh and critical selection for suitable parents at each generation. That way, over time, the breeder can get an idea of which will produce what.

I had a very interesting discussion with a geneticist about inbreeding. Apparently, they don't consider a line of mice to be inbred until they've bred at least 30 generations, brother to sister -- and then they are only considered inbred for the characteristics they've selected for!

Inbreeding is a matter of degree. All breeds are inbred to a certain extent which is why they share common characteristics. Inbreeding no more "causes" faults than out-breeding will cure them. So the violent out-crossing of dog breeds to produce designer mongrels is misdirected. It won't cure the faults but it may conceal them in the short term.

Breeding is like computers: Garbage in, garbage out.

 

[RutlandH2O]

Inbreeding is perfectly OK provided the offspring are 100% perfect in every way!

The problem is, you won't know that until you've bred -- and even then your super-dooper foal may be a one off by sheer luck with every other bred the same way a total dud.

The great farm livestock improvers never revealed their pedigrees and I suspect there are more lies in the published pedigrees than are ever told in court. DNA testing has revealed what many would have liked to have remained hidden!

Line breeding is something that needs to be done over many generations with very harsh and critical selection for suitable parents at each generation. That way, over time, the breeder can get an idea of which will produce what.

I had a very interesting discussion with a geneticist about inbreeding. Apparently, they don't consider a line of mice to be inbred until they've bred at least 30 generations, brother to sister -- and then they are only considered inbred for the characteristics they've selected for!

Inbreeding is a matter of degree. All breeds are inbred to a certain extent which is why they share common characteristics. Inbreeding no more "causes" faults than out-breeding will cure them. So the violent out-crossing of dog breeds to produce designer mongrels is misdirected. It won't cure the faults but it may conceal them in the short term.

Breeding is like computers: Garbage in, garbage out.

^^^This! We've just overlapped our posts.

 

[s4sugar]

Inbreeding is perfectly OK provided the offspring are 100% perfect in every way!

The problem is, you won't know that until you've bred -- and even then your super-dooper foal may be a one off by sheer luck with every other bred the same way a total dud.

The great farm livestock improvers never revealed their pedigrees and I suspect there are more lies in the published pedigrees than are ever told in court. DNA testing has revealed what many would have liked to have remained hidden!

Line breeding is something that needs to be done over many generations with very harsh and critical selection for suitable parents at each generation. That way, over time, the breeder can get an idea of which will produce what.

I had a very interesting discussion with a geneticist about inbreeding. Apparently, they don't consider a line of mice to be inbred until they've bred at least 30 generations, brother to sister -- and then they are only considered inbred for the characteristics they've selected for!

Inbreeding is a matter of degree. All breeds are inbred to a certain extent which is why they share common characteristics. Inbreeding no more "causes" faults than out-breeding will cure them. So the violent out-crossing of dog breeds to produce designer mongrels is misdirected. It won't cure the faults but it may conceal them in the short term.

Breeding is like computers: Garbage in, garbage out.

Absolutely!

 

[E13]

So the problem with inbreeding is basically that it increases the risk of problematic genes being expressed? But then if you don't know what your horse/dog might be hiding, well surely you also don't know what the 'outsider' animal you breed to is carrying? Taking hip dsyplasia as an example, if you bred GSD to GSD, without health tests, there is a risk of HD, but if you bred GSD to say labrador, again with no tests, is that the same risk, or is one more risky?

 

[HBM1]

That is too close for me. I have no problem with what others do, but for me, although I don't mind similar grandparent lines (not exactly the same though), or great grandparent, I would not get closer than that.

 

[HBM1]

So the problem with inbreeding is basically that it increases the risk of problematic genes being expressed? But then if you don't know what your horse/dog might be hiding, well surely you also don't know what the 'outsider' animal you breed to is carrying? Taking hip dsyplasia as an example, if you bred GSD to GSD, without health tests, there is a risk of HD, but if you bred GSD to say labrador, again with no tests, is that the same risk, or is one more risky?

I don't breed dogs, but have bought plenty of puppies in my time. I always check if the breeder has had their dogs tested for hip dysplasia etc...unless I was getting a puppy from a rescue centre, I would insist on that, given the prices they charge.

Re horses, I stick to the known and proven bloodlines, which for me, helps to lessen anything arising.

 

[FinnishLapphund]

So the problem with inbreeding is basically that it increases the risk of problematic genes being expressed? But then if you don't know what your horse/dog might be hiding, well surely you also don't know what the 'outsider' animal you breed to is carrying? Taking hip dsyplasia as an example, if you bred GSD to GSD, without health tests, there is a risk of HD, but if you bred GSD to say labrador, again with no tests, is that the same risk, or is one more risky?

As I understand it, statistically I would say that it is about the same risk for the puppies in your example to get HD. But perhaps HD is a bad example, the last I heard about it, they think that there is probably several recessive genes that can cause HD, and that over feeding a growing puppy can cause HD, and perhaps also far too much or far too little exercise whilst growing, possibly in combination with the "wrong" recessive genes...

And there is yet no gene test available for HD, there is only HD x-ray, so even puppies with parents that is HD clear, can develop HD, but the risk is much lesser/there is less risk for a severe HD fault, that leads to that the dog either needs to have the HD fixed by surgery or be euthanised.

But there is several "easier" diseases (easier only meant as in regarding the way they're inherited, nothing else) that you can use as an example, diseases where the puppy needs to inherit one "wrong" gene from each parent to get the disease. From a post/thread I wrote last year ( http://www.horseandhound.co.uk/forums/showthread.php?t=590653 )

But genes doesn't care about innate healthiness, if they're duplicated - they're duplicated, no matter if you cross a Spanish Water Dog with a Nova Scotia Duck Tolling Retriever, or a Cocker Spaniel with a Dwarf Poodle, all those four breeds can carry the eye disease gene prcd-PRA, and if it is duplicated - it is duplicated.


Another example, let's say that we cross a Beagle with a Shetland Sheepdog, some of the puppies inherit the eye disease gene for POA Glaucoma from the Beagle, one of those puppies becomes a broodbitch that is mated back to another Beagle, if that leads to a duplication of the gene for POA Glaucoma, then this new fashionable, "innate healthy" Beagle/Shetland Sheepdog crossbreed can have the same inherited eye disease POA Glaucoma, as a purebred Beagle.


Optigen offers some different DNA-tests for dogs, for example :
If you have a Golden Retriever it can be tested for 3 diseases (prcd-PRA, GR_PRA1 & Ichthyosis).
If you have a Labrador Retriever it can be tested for 3 diseases (prcd-PRA, RD/OSD & NARC).
If you have a Labrador/Golden Retriever cross it can be tested for 4 diseases (prcd-PRA, GR_PRA1, Ichthyosis & RD/OSD).
If you have a Goldendoodle it can be tested for 4 diseases (IC, prcd-PRA, GR_PRA1 & Ichthyosis).
If you have a Labradoodle it can be tested for 4 diseases (IC, PFK, prcd-PRA & RD/OSD).
If you have an Australian Labradoodle it can be tested for 5 diseases (IC, Ichthyosis, PFK, prcd-PRA & RD/OSD).
If you have a Labradoodle/Goldendoodle cross it can be tested for 6 diseases (IC, Ichthyosis, PFK, NARC, prcd-PRA & RD/OSD).
( http://www.optigen.com/opt9_test.html )

About horses and inbreeding, I read a while ago something about Standardbreds/Harness Racing Trotters and inbreeding (e.g. almost all Swedish Harness Racing Trotters goes back to Peter the Great, 1893–1913, or to his grandsire's sire Hambeltonian 10, 1849 – 1876), as I recall it, the conclusion was that horses seemed to be less vulnerable to inbreeding than for example dogs. But that is the situation now, e.g. give it 10, 20 or more years, and who knows, maybe they won't continue to be less vulnerable for ever.

 

[Penumbra]

Inbreeding isn't just a problem for causing genetic defects though (although this can be a major problem). If inbreeding is sustained for many generations, you often get a very amount of different genes (alelles) in the population. This can be problematic, as a wider variety of genes in a population is often advantageous as some versions of the gene may confer resistance to new diseases. A wider variety of genetic material also enables the breed to be more adaptable.

I'm coming at this from a conservation point of view and obviously the genetic problems in conservation are different to those in domestic animals, but I do think the loss of genetic material from relatively small populations is worrying in all animals.

This doesn't apply to simply breeding brother and sister together once, but sustained inbreeding within a population, which I think is more likely to be common if this level of inbreeding is viewed as acceptable.

Also, in many cases, individuals which are more heterozygous (two different alelles of a gene) tend to be "fitter" than those that are more homozygous (two of the same alelles), so I would always chose to outbreed, unless the population was already so inbred, that the brother and sister were actually less related.

I think very closely related matings, such as full siblings, siblings and parents, and to a lesser extent, half siblings and uncle/niece pairings should be avoided where possible, and shouldn't be happening every generation. This does often affect reproductive success if it goes on for a long time, too, which is a reason to avoid it.

So I think as a one off, it can be successful, but it shouldn't be seen as best practise, as it has come to be seen by some pedigree dog breeders. I do understand the logic behind it, but these things often come with unforseen consequences.

 

[Pearlsasinger]

quote "there is an old saying ' line breeding if it works, inbreeding if it doesnt'

full brother & sister to me is a nono"

Quite and how many undesirable genetic conditions have been bred into dogs, horses, cats and other species, just because the breeders wanted to breed for looks?

I have taught children whose families have been in-bred for several generations, with cousins marrying cousins, or two brothers marrying two sisters and the resultant offspring (cousins) marrying each other. Far too many of these children had physical deformities or other health problems.

 

[Jenni_]

quote "there is an old saying ' line breeding if it works, inbreeding if it doesnt'

full brother & sister to me is a nono"

Quite and how many undesirable genetic conditions have been bred into dogs, horses, cats and other species, just because the breeders wanted to breed for looks?

I have taught children whose families have been in-bred for several generations, with cousins marrying cousins, or two brothers marrying two sisters and the resultant offspring (cousins) marrying each other. Far too many of these children had physical deformities or other health problems.

What kind of job requires that Pearlsinger? I'm intruiged!