I was browsing another site, where there was an active breeding discussion going on, and the reason someone put forward for not going to 'show' breeders was because they lower the gene pool by only using certain lines, and not outcrossing to unknown linesand widening the gene pool. Anyway, a poster came up with this condition, which I don't understand and wondered if anyone here did? it was hetrozygote advantage. Discuss?

I haven't studied heterozygote advantage enough to have a valid opinion on it, I'm afraid.

>'show' breeders was because they lower the gene pool by only using certain lines,

Has anyone countered this with the suggestion that it's often 'pet' and hobby breeders who use the champions just to get some 'red' on the pedigree regardless of the suitability of the dog, and thus limit the gene pool themselves?

No JG, the one person holding their own on good breeding seems to have stopped the thread by asking the ones that breed what are their reasons for breeding, after making a comment that unless bred for a purpose, which they list, why breed a litter at all. Except for the money :rolleyes: It was that H advantage thing, I couldn't understand it, I wonder if the poster did, or was just using a phrase to sound as if they knew what they were on about ;)

Can't claim to fully understand it either but it is something to do with natural selection I believe in which case I would say those that churn out puppies outside the show world appear to be even more likely to use limited genes as they will have a stud, on hand, that they use again and again so the strengths of natural selection are even less likely to be found there.

http://medicine.jrank.org/pages/2382/Heterozygote-Advantage.html

As I understand it, the term Heterozygote Advantage is basically what many term (in layman's language) HYBRID VIGOUR!  particularly in relation to dogs and domestic stock.  Ie mixing different strains (or breeds ;) ) will produce greater health advantages than using pure strains (or purebred dogs) 

Only works in the first cross though.  Further breeding from the offspring will not have beneficial results at all.

Used commonly for meat Rabbit production.  The New Zealand males are mated with the Californian does and Vice Versa, but the breeding stock are kept pure. 

Selection of breeding stock is based on production.  Records are kept of how much food is used in the weeks from parturition to killing weight used by the doe and litter.  The ones with best food conversion rates are the ones to bred from. 

With certain recessive traits hiding/diluting it doesn't get rid of it, this just means it's spread around the gene pool to reappear in many of the dogs several generations later, by which time it's very difficult to breed out as the gene/genes may well be so well established that it's difficult to find dogs without the gene in their background :(  not something you'd want if it's also a disease that only shows up after the age a dog would have been bred from :(

Thinking of CT and hyperkeratosis here for starters

this is where judicious close breeding can expose any skeletons.

When using an outcross it is a good idea to breed close a few times before it has been used too much to check.

Many puppy farmers so exactly the same except they produce larger volumes.  they will use the one stud dog on all their bitches and often mate close relatives purely as it is convenient, and no selection for health etc is done.

Casual breeders can end up doing exactly the same, especially in popular breeds.  the reason is that in popular breeds people are less likely to travel far to buy their pup so the local population of GSD Labs etc are likely to me more or less related, and with no health tests, the situation is not good at all.

I would far rather go with a knowledgeably line bred litter with generations of health testing, as you know what your playing with.  Outcrossing completely is OK for the first generation but the bad things are simply masked and will out down the line.

Most good breeders stock is far less inbred than is popularly thought.

The Finnish kennel clubs database is open to anyone and the pedigrees for my breed show about the same amount oflinebreeding as we See here and yet the inbreeding co-efficients are not that high (the pedigrees show these it is quite interesting and you can take pedigrees way back).

How many times should a stud dog be used say per year in order for the lines not to be diluted? at what point do you look at a breeder and say hang on thats not looking right?

I take it you mean how often would a dog be used to be overused.

That is a difficult question.  It all depends on how many litters are bred in the breed as to what constitutes overuse.

It is complicated even further in that a dog that was judiciously and sparingly used can become overused if he was good by the use of his offspring.

In my breed where we normally have around 20 litters bred a year a dog used three times a year would be being used a lot.

Our imported boy has only sired 8 litters in the UK (2003 to 2006), but he has produced well, and a lot of the current Young stock in the ring are by him and now his grandchildren, and he has only been used by 3 of his owners and one other.

We will never recoup his import costs, in stud fees, lol :D :D :D   but that level of use from a population point of view is more than enough.  It meant with his daughter I was in the same position as with her mother all the young males I liked were closely related to her, and had to take the chance of an outcross again, this time travelling abroad rather than importing a husband.

Just out of interest.  My first home bred bitch was a nice typical bitch but nothing great.  She had 3 litters, 17 pups in all.  I kept one, who herself had 17 puppies.  A male son from second litter has sired 5 litters, and another bitch was exported and was bred from.  So it isn't just the first generation that will be influenced and you need to think always what will there be in the next generation if I use this dog or bitch.

In a numerically-strong breed there'd be no reason to use a dog more than a couple of dozen times in his entire life. And if he hadn't sired anything of real merit in his first 6 litters or so then he's probably not really worth using more.

Yes but what I was saying even 6 times in a breed like ours is a lot for good or ill.  If the offsprign turn out poor they will still ahve influence beyond that what they would in a numeerically strong one.

You can find that you are linebreeding to a dog you don't want to linebreed to, because you can't go back to the drawing board.

To be honest for there to be any advantage to random breeding natural selection needs to coem into play, this just doesn't happen much in domestic livestock or humans which is why there are more genetic diseases that survive long enough to reproduce.

I was just going to say something similar Brainless. I don't know diddly about breeding dogs but I've worked in genetics for many years. The healthiest dogs would arise from wild populations left to breed on their own accord. Of course this also assumes that the population would be made up of those who were best able to survive in their environment. The ones who were unfit would not survive to reproduce.

The complexity of genetics is an interesting thing though. Often by selecting for one trait you end up selecting for another unintentionally. Take HD for example. What if selecting for dogs that have good hips introduces another genetic defect like propensity towards cruciate tears (totally made up, just using this as a hypothetical question). I just finished a book where the author calculated how many generations it took to begin inbreeding after a stud book closed. It's really quick in breeds with smaller numbers and happens all too quickly in those with large numbers as well. Most breeds have only been bred pure in the last hundred years (think I'm right on that but no guarantee) so 100 years ago most breeds still had fairly mixed bloodlines. In another 100 years will breed clubs have to open their stud books and breed some hybrids to reinvigorate their dogs. It will be interesting to find out. :)

Often by selecting for one trait you end up selecting for another unintentionally. Take HD for example. What if selecting for dogs that have good hips introduces another genetic defect like propensity towards cruciate tears (totally made up, just using this as a hypothetical question).

A couple of points springs to mind here. First Syringomyelia in Cavaliers (or whatever they call it now, think it is Chiari-like Malformation they decided on officially!) is believed to have appeared very early on when the Cavalier was bred from the King Charles Spaniel (for those that don't know, a rich American awarded a cash prize at Crufts for 5 years in the 1920's to the breeder who managed to produce a dog that most looked like those in old paintings, as the King Charles Spaniel had gradually got a shorter and shorter face, and this American liked the longer nosed examples of the past, so breeders outcrossed to other breeds to produce what eventually became the Cavalier KCS, and so selection was on looks ONLY), but is now becoming more common -possibly because people have been trying to breed out MVD. I.e. concentrate too much on one defect and another comes to the fore.

The other point being I remember reading a show report once from a Golden judge who had judged abroad (I shall let the country remain anonymous) and they said all the dogs they met had wonderful hip scores but terrible temperament as hips had been selected for above temperament.

Of course, it shouldn't HAVE to be like this, one thing should not preclude the other, but it makes it all a lot more complicated. I know this only too well in my cats where I had to breed out a genetic defect (and therefore had to select healthy breeding cats regardless of looks in order to save my lines) and ended up with healthy cats that sadly did not look much like their breed any more. It's taken me 3 years so far and I reckon a few more before I once again breed Champions. (In 2001 I made up 5 titled cats, since having to select for health ONLY, none!) But it WILL happen.

In another 100 years will breed clubs have to open their stud books and breed some hybrids to reinvigorate their dogs. It will be interesting to find out.

Personally I don't think so, not now when we CAN all go abroad and get fresh blood that way. Certainly in Malinois it is the way we are going here as the dogs are all getting very closely related in the UK (such a small genepool!) and I know that I myself will HAVE to go abroad in the very near future as there is very little available here that I can use.

Or our understanding of heredity will improve so that we can safely breed within the gene pools, trying our best to keep necessary genetic variation.

I think the best breeders have always known by gut when to breed out.  It takes someone to look carefully at traits vital to health and vigour.  Bitches that whelp without difficulty should be selected over ones that have problems, those whose pups are really vigorous and good doers etc.  I wouldn't keep back fro breeding any pup that was problematic to rear. 

Once natural selection is removed then the responsibility on breeders is immense and therefore not something to be dabbled at.

One breed that seems to be very healthy is the Lowchen, and it had very few founders.  they were lucky I suppose that the foundation stock didn't have any serious recessive health traits.

>Once natural selection is removed then the responsibility on breeders is immense and therefore not something to be dabbled at.

That's right. Those who struggle to rear sickly whelps which might go on to be bred from later aren't doing their breed any favours. Sentiment has little part to play in responsible breeding.

I think people have to be responsible when traits (unexpectedly) rear their heads, even though you chose your breeding bitch for all the right reasons. I recently had a girl with total inertia.  I couldn't believe how totally flaccid the uterus was.  The 5 whelps are a lovely size, strong, healthy and thriving.  There are 3 bitches in this litter.  I have thought long and hard before making my decision.  I feel very strongly that we should be using self whelping bitches, and this is a very small toy breed (that I wouldn't normally expect to have 5 pups.)  I'm responsible, and use girls at the upper end of the breed standard for weight, and extremely small, fine boned boys, with self whelping in mind.  Even with the use of Oxytocin, this girl was unable to have contractions.  She is going to be spayed and kept as a much loved pet.  It is my responsibilty to ensure the bitches go to pet homes only, and are never used for breeding.  They will not be registered, and interested people will have to jump through hoops to get them!  So I do feel that I am doing the responsible thing, in case the inertia is genetic.

Now that might be throwing the baby out with the bathwater. 

I agree I would spay the dam, but if it is as case of loosing the line I would keep the best of the daughters and mate her, and only terminate the line if she had problems too. 

After all it was a large litter and  this problem can occur even in the easiest whelping bitches.

One of my own bitches had inertia with her last litter, and needed a C section.  by then I had already bred from her daughter and other descendants all with no problems, it was just one of those things.