I've said it lots of times on here - I'm so uncomfortable with line- and in-breeding. But was just reading an article about humans which found a probably biological basis for increased fertility in couples related at the level of 3rd or 4th cousins. Wonder if similar could be the case in animals?

http://www.sciencemag.org/cgi/content/short/319/5864/813

My understanding of line breeding was that it can have a very quick and positive impact of the bloodline, setting traits, stabilising gene effects, if appraoched in a moderate manner, such as you have discoverd in your research on humans. no closer than say grandfather over grand daughter, nephew over auntie, grandson over grand mother or aunty.
I feel when line breeding becomes inbreeding, son over mum, father over daughter or even brother over sister this is when you can run foul, doubling up on bad genes faster than the good ones, just because you might miss the bullet once or twice eventualy gene degradation will set in, personality and stability seem to be the first casualties, then mental soundness followed by physical issues and it's all down hill.
Not worth it from my point of view, we'll get there wherever there is, all in good time, rushing never proved anything.

well i am safe from line breeding at this time the closet's i have is two half sisters spice and summa came from the same mother but different fathers that came from different states. Quin and Mirra may be related in some way but there is only a small chance of that they were born and breed 230kms away from each other so i think i am safe there. And Greyson is not related to any of them that i know of. i have done line breeding in the pass with the cavies and i had no problems but the rule of thumb is never put son over mother brother over sister these are the two bad ones, father over daughter is not as bad for some reason but i did not go there but i did line breed very close as i had trouble finding new blood lines and the new out cross's that i did find introduced bad traits such as small ears longer muzzles piggy eyes i would pick out the best sow out of these pups and get rid of the rest including the new out cross then put this sow (say it has bad colour that has come through from the new blood) to a boar with the best colour plus good ears and eyes to fix up and reset the traits that i already had in my lines by breeding this way i had big robust animals and i had breed over 9 champions in 8 years and i started with inferior stock

I think with both line- and in-breeding, you can get great things and you can also get awful things and it's kind of luck which it is (or if it's both). If the *connecting* dogs have good features, you might double up on them, which is great. But they might also have less good features, they might be doubled up too.

But what really worries me is that you might double up on nasty recessives that have been hiding. I've heard of some breeds where a few dogs have been taken to a new country and fairly closely bred for a while and nearly all the individuals have a particular disease because one of those original dogs carried it. If there'd been more dogs in the gene pool I still suspect that eventually those genes would get pretty widely distributed and meet up.

And I worry about the capacity of genetic testing to keep up with random nasty mutation.

We have always heard in the dairy industry that it's line breeding when it works and inbreeding when it doesn't.
I think it all relates to what traits are strong or weak in the line that you are using, if there are any obvious bad traits I wouldn't even consider it because they will all be magnified. I would only consider it any closer than a common grandparent if you feel you are in danger of losing the line and it is extremely good quality. With cattle we have had success using a common grandparent when it has been a top quality animal. I think with the club and register we can find enough good koolies to choose from without having to use a related dog. The results of DNA so far has shown us we have very good diversity, better than many other breeds (who have often all bred to the same line as different ones win best of breed or like).

And when you're breeding livestock there's always a purpose for the progeny, even if they don't fulfil your hopes.

Hi Silhouette,

I don't think that line breeding and inbreeding are the same thing.

As far as I have always been told it is only inbreeding if there are not 2 generations between the dogs, people etc.

These parameters are set in so many places to ensure that not many problems would ensue.

As you would know a lot of medical conditions often skip a generation and appear in the second generation without appearing in the first the same goes for genes as they often appear in the second generation as well.

So the routine for line breeding was set at a minimun of 2 gererations between the dogs, people etc.

This should prevent any increase in intensity of a bad gene and should cause a dilution effect on bad genes and medical issues.


Hope this makes sense

Jack @ Wilja Koolies

Hi Jack
That statement was always tongue in cheek, a glib reply depending on whether the experiment worked or not.
Conditions may show up in the 2nd generation because they are a recessive gene and by in breeding both parents are carrying the gene and the offspring inherit one copy from each parent so it is active in them. Some would carry the gene in a recessive form able to express itself in later generations still.

According to my genetics text book (so I'm an expert ;-), genetists do not usually distinguish between in- and linebreeding. They are the same thing, just at different degrees. They would rather merely be interested in calculating the percentages of inbreeding. The chances of getting the benefits and the risks from such breeding practices are less in the case of linebreeding, but nonetheless still exist.

Reading back over what I wrote at the beginning of this thread I'm cringing. Doubling up!! Eek. Makes it sound like the dog might have 2 heads. I mean increased homozygousity, and reduced heterzygousity, of course.

From memory, I think 6.25% inbreeding is considered acceptable to the scientific mind. But there is more to breeding than numbers and chances and that is knowing your own lines, how they breed and what good points can be magnified while at the same time minimising faults. That only comes with a lot of practice building your line and perservering. I get frustrated in our line (dairy) with the amount of people who go out and spend big money to buy the best or off the best assuming it's an easy thing to continue their hard work to this point. But many fall flat as they don't know how to match the two potential mates. Good mated to good doesn't always make better. It is something that comes with practice and not a cheque book.
I would say a common grandparent (as long as it has no major faults) is an acceptable level, not sure if this equates to 6.25% or not.

Yes, genes are so complicated. And so many characteristics are the result of interaction between genes that breeding together 2 'correct' animals doesn't provide any guarantees of success (like that of height versus bone thickness, and genes for hip laxity). Personally I'm more interested in the characteristics that a particular dog can produce in it's pups than what it is like itself, and what it's progeny can then produce.

I'll have a look at my book later and see if I can find what the percentage would be for a shared grandparent.