" Hybrid Vigour"

[Leema]

How do you respond to those who argue that dogs who are cross bred are genetically superior due to hybrid vigour?

The more detail the better. :)

[~Anne~]

As I understand it, hybrid vigour relates more truly to a mix of species.

In canines of different breeds it is still the same species. However, as it has been argued here a million times, outcrossing certainly can benefit. Recessive and dominant genes are still recessive and dominant genes and the traits of the genes are found broadly in all breeds of dog.

That's my understanding anyway and it could be wrong as I am not a scientist I have not studied genetics in any shape or form.

Edited April 6, 2013 by ~Anne~

[Kirislin]

Hybrid vigour or not, each parent needs to be healthy themselves to produce healthy offspring.

[mita]

There's a sharp critique of how 'hybrid vigor' is being claimed as making mixed breed dogs biologically superior to purebred dogs .... from a vet, Dr Libbye Miller. If someone genuinely wants to be informed, then give it to them to read.

http://www.facebook.com/note.php?note_id=443915662016&id=1584362759

Sample opening paragraphs. But read the lot, not long & not a word wasted. Note that permission is given to repost. Or print it out to pass on:

"Adorable mixed breeds" get cancer, epilepsy, allergies, heart disease, and orthopedic problems just like purebreds. I see it every day in my veterinary practice but mixed breed dogs aren't tracked like the purebreds so they have a reputation as "healthier" that is actually undeserved in many cases."

It is so sad that a lot of folks, including young veterinarians these days, buy into the "hybrid vigor" baloney. The vet schools have been infiltrated by the Animal Rights Extremists, who are teaching them this junk science in order to push their agenda.

All animals have a certain amount of genetic load, which is to say there is absolutely no animal without some genetic problem of some sort of another. Know anyone who wears glasses? Has allergies? Thyroid problems? Weak knees? Flat feet? A skin condition? Arthritis? A gapbetween their front teeth? These are all genetic imperfections.

No human is genetically "clean." Neither is any individual of any species on earth. So this idea that dogs should not be bred because they might have a genetic problem, and that breeders are somehow "evil" for breeding them, is ridiculous. Every single individual of every single species has at least a few genetic conditions....

And the rest, too!

Edited April 6, 2013 by mita

[mita]

This article points out, more technically, why claims that crossbreeds always have 'genetic superiority' is not science.

Also says the very term 'genetic superiority' is a value judgment & not science.

Explains why Dr Miller describes such claims as 'junk science'.

Scroll down to From Wikipedia on Answers. com: heterosis (hybrid vigor). Next to pic of mixedbreed dog. Couple of paragraphs under Controversy: Worth printing out, too:

http://www.answers.com/topic/heterosis-1

Edited April 6, 2013 by mita

[Steve]

How much do you want ?

There is a difference in how a good purebred modern dog breeder uses in breeding as a tool and random population studies for a start.

Profiling a pedigree which can identify recessives,mutations, diseases etc before a mate is chosen can have a huge impact.

Then of course we have all the modern technologies and resources too such as DNA X rays, scans and specialist testing we can use. We're not considering animals which are inbred from a natural occurrence due to isolation etc which is usual in studies with population genetics but we are manipulating which mates to use.

Without manipulating the matings things such as environmental factors [ such as loss of habitat] deficiencies in soils which lead to nutritional deficiencies etc have to also be considered as to how they may affect the study results.

Usually when a scientist goes after an answer only one variable is looked atwhen in fact their study results may have been impacted by many others

Next - not only are we talking about breeding animals of the same species but many of the genetic issues modern purebred breeders have to contend with are not recessive issues. Polygenic genes cause us more grief than most others and the contributing factors are in all dogs .So outcrossing doesn't eliminate the potentials for seeing genes which are affected by things other than recessives BECAUSE we are still breeding the same species. If the unrelated strains share common genes for genetic disorders, no amount of hybrid vigour will over ride the risk of the disorder showing up.

Hybrid Vigour only applies to the animals that are the direct offspring of the crossing of the unrelated strains. In other words if you continue to breed animals of different strains there generally will not be any additional increase in hybrid vigour. Out-crossing can also cause problems .

Short answer is that there is nothing "wrong" with breeding any two animals of any degree of relatedness, as long as the breeder realizes the potential risks and benefits of the mating. Any level of inbreeding does carry some risk (the risk that one or more formerly hidden recessive traits will be expressed in the homozygous offspring), but there is also the potential for benefits .

Each breeder has to weigh the potential costs and benefits and assess which strategy best fits his or her long term goals and interests and they shouldn't be frightened off making those decisions by propaganda spread by those trying to discredit what a purebred breeder does in order to promote crossbreeds.

There are also new developments in the science field which may show that not enough emphasis has been put on the nutrition and environment of consecutive generations in studies to date on inbreeding and population genetics – what grandma ate is now being found to have an impact on the health and longevity of the granddaughters .This may prove to impact on what has been blamed and namedas an inbreeding depression. Nutrigenomics is another science to be considered.

Take a different perspective on how you look at nature and you will see Animals striving everywhere to produce homozygosity - They don't have any

Instinctive safeguard against incestuous mating? Nup. Reproduction in rats, mice,rabbits and other rodents, takes place without any regard for relationship, and these animals are notorious for their fertility and vigour. Among antelopes incestuous matings are the rule.

The African reedbuck, for instance, has two young at a birth, male and female, which mate together when mature. Only when one happens to die by accident does out- or cross-breeding occur and this is true of the smaller antelopes too, it's the same with red deer. Brother and sister tigers mate as the norm and among African buffaloes, breeding occurs mainly among the immediate offspring of the same cow. The cattle from La Plata in the Falkland Islands, not only quickly multiplied from just a few , but they also broke up into smaller herds according to colour, and the close inbreeding became more intensive because of the cattle's own instincts.

Many animals do chase off the younger males and don't let any new comers in sothe, males mate with their own daughters.

in nature among some monkeys constant matings between the head of the horde and his daughters, sisters and other close relations,happen. Among most animals, including elephants , the leading male mates with his daughters, grand-daughters, and great-grand-daughters, as long as he is able to keep other males away. Even when he isn't strong any more that doesn't stop the incest because usually it will be one of his sons which take his place.

Have a look at the rabbits and foxes of Australia and these are all theoffspring of just a few individuals

In New Zealand the red deer began as 3 and were introduced in the 1800's from England and last count about ten years ago the herd numbered over 5,000. They show no signs of disease and they are superior in vigour and health to the original parent stock.

A fellow called Kronacher, starting with one male and three females (a mother and two daughters) of ordinary goats, and in bred for eight generations, without any loss of size, physical development, milking capacity, fertility or vitality. In fact their fertility tended to increase.And he declared that in this case he practiced no selection whatever.

In 1916 Professor Castle stated that he had successfully bred Drosophila, brother and sister, for 59 generations, without obtaining any diminution in either vigour or fertility. Moenkhaus crossed the same fly, brother and sister, for 75 generations, without harmful consequences.Hyde and Schultze achieved the same result with mice. Castle tried rats, and Popenoe guinea-pigs, and both concluded that no deleterious effects could be ascribed to the in bred system of mating. King experimented with white rats,mating brother and sister regularly for 22 generations, and among these inbred rats some were obtained which proved actually superior to the stock rats from which they had sprung. The males were 15 per cent. heavier, and the females 3 per cent., while the fertility was nearly 8 per cent. Higher.

In old Egypt,national law didn't allow mixing with foreigners, incest was common both among the people and within the ruler groups. Cleopatra, famous for her wit, beauty and intelligence, was the daughter of a brother and sister,great-grand-daughter of another brother and sister, and a great-great-grand-daughter of Berenice who was both cousin and sister to her husband. In Britain,as late as fifth century, Vortigern married his own daughter. Nor could the practice have been condemned, since the son of this sinful union was none other than St. Faustus. The ancient Irish married without distinction their mothers and sisters, and it was customary for the ancient Germans to marry their sisters. There is overwhelming evidence that the Peruvians were strictly inbred . The Incas, refused to mix their blood and married their sisters; More modern studies in human population genetics are The Pitcairn islanders, theKisar Hybrids, the Bastards of Rehoboth, and the people of the island of Batz, all of whom are examples of human breeding with close inbreeding without harmful results. Even in tribes and races where incest is illegal, often the rulers or chiefs deliberately breach laws to keep their blood pure. For instance in several countries, marriage with half-sisters is forbidden, but the King always marries his half-sister. may marry his sister and his daughter. Eg.Cambodia, the chiefs of the Marianne and Ladrone Islands,in Hawaii, Nukuhiva, Tahiti and Madagascar, and it was also true of the Northern American Indians of New England. Nor are the people who do inbreed degenerate or diseased, and travellers comment on their great vigour and beauty.

With the Fijians — those stocks which have adhered to the ancestral custom requiring first-cousin marriages, are very much the superiors from every physical point of view of those who no longer practice or else forbid,first-cousin marriages, and the latter are even said to be dying out, while the former have a higher birth rate and greater vitality.

The Bataks of Sumatra, who also habitually marry their first-cousins, are some of the healthiest people in the Indian Archipelago. The chiefs in Polynesia and New Zealand have all been noticed for their superior height, looks and vigour. And throughout Polynesia the closest inbreeding in mating is among the chiefs.

Therefore, humans are just as capable as some of the animals of thriving on close inbred matings.

Fact is that it isnt about how closely in bred an animal is but rather what it has been selected for . You get what you focus on and loose what you dont - so unless fertility and health is one of the priority goals it may be diminished - the major point is we in breed in order to be able to have predictable animals and a good breeder will breed for health , vigour,longevity and fertility as well as whatever else they are selecting for. Its still about the breeder and its still about the ability to ensure that future generations have predictability to enable better responsible choices about which dogs suit a person's lifestyle.

Its still about the breeder

Its still about the breeder

Its still about the breeder

Edited April 6, 2013 by Steve

[trinabean]

I stay out of arguments about 'hybrid vigour' as unfortunately, I have a very sickly pedigree.

[Steve]

I stay out of arguments about 'hybrid vigour' as unfortunately, I have a very sickly pedigree.

No doubt about it some lines and some breeds have some big issues to deal with but this is about selection not in breeding.

It wont be magically fixed for consecutive generations if we just start outcrossing - in fact in may give us more grief than we have now

[Mrs Rusty Bucket]

So if you cross two different breeds, puppies known as an F1 cross (I think), then I think you get a greater genetic diversity. Which is theoretically genetically superior as in there is a greater spread of "mutations" or variations or adaptations or something - so if there is some sort of adverse event (not enough food, too hot, too cold) then it is more likely with a genetically diverse population that enough will be able to survive what ever it is and breed.

Some farmers also argue an F1 cross of sheep or cattle - gets you bigger healthier animals - which might explain why a poodle x GR can be bigger than the biggest GR or poodle. I think you have an almost equal chance of getting smaller animals.

There is also a counter argument to select to minimise faults so you have a very small gene pool but they don't have any unhealthy mutations (like haemophilia). However a group of animals (or humans) with a very small gene pool is prone to mass death if they are exposed to something they're not adapted to / vulnerable - eg the Koala populations on KI - limited gene pool, unlikely to do well repopulating NSW - they will just get sick and die of the first NSW koala virus they get.

The most obvious argument to toss at your hybrid vigor people eg the poodle cross websites that claim "multi generational" and "sound health with a hybrid vigor" - is that as soon as you get away from the F1 cross and start crossing the cross breed puppies, you start limiting the gene pool again, and you lose any advantages of "hybrid vigor" after the first generation. So "Multigenerational hybrid vigor" probably qualifies as an oxymoron.

If you stay with the F1 cross - you can't guarantee any kind of desirable outcome like coat type or allergy rating or even temperament. The original lab x poodle breeder was sorry they ever came up with the gimmick name.

Of the three pups, he [the blind customer] was not allergic to one of them. In the next litter I had there were 10 pups, but only three had non-allergenic coats. Now, people are breeding these dogs and selling them as non-allergenic, and they're not even testing them."

In the wider animal kingdom - a creature like a mule - might be bigger and stronger than it's parents, but - is usually unable to breed. Hybrid sterility.

Which is sometimes a good thing. But the edges of species does tend to be a bit blurry. They're having to rename whole plant and fish species and families at the moment.

[trinabean]

I stay out of arguments about 'hybrid vigour' as unfortunately, I have a very sickly pedigree.

No doubt about it some lines and some breeds have some big issues to deal with but this is about selection not in breeding.

It wont be magically fixed for consecutive generations if we just start outcrossing - in fact in may give us more grief than we have now

Absolutely Steve, and I wasn't suggesting outcrossing. I still prefer the predictability of living with purebred dogs.

I more meant that my own dog is, sadly, not a great example to use in arguments about the health of pedigree vs the 'hybrid vigour' of crossbreds. I wish it was different.

Edited April 6, 2013 by trinabean

[Steve]

I stay out of arguments about 'hybrid vigour' as unfortunately, I have a very sickly pedigree.

No doubt about it some lines and some breeds have some big issues to deal with but this is about selection not in breeding.

It wont be magically fixed for consecutive generations if we just start outcrossing - in fact in may give us more grief than we have now

Absolutely Steve, and I wasn't suggesting outcrossing. I still prefer the predictability of living with purebred dogs.

I more meant that my own dog is, sadly, not a great example to use in arguments about the health of pedigree vs the 'hybrid vigour' of crossbreds. I wish it was different.

Yep I got that was what you were saying but there is a big push on for us to outcross and crossbreed - there is a good argument for that in some breeds but its not something that can just be done with no science if its going to help and still leave us with individual breeds.

[HazyWal]

I stay out of arguments about 'hybrid vigour' as unfortunately, I have a very sickly pedigree.

No doubt about it some lines and some breeds have some big issues to deal with but this is about selection not in breeding.

It wont be magically fixed for consecutive generations if we just start outcrossing - in fact in may give us more grief than we have now

Absolutely Steve, and I wasn't suggesting outcrossing. I still prefer the predictability of living with purebred dogs.

I more meant that my own dog is, sadly, not a great example to use in arguments about the health of pedigree vs the 'hybrid vigour' of crossbreds. I wish it was different.

Trina...he's a lucky boy that he's a bean.

[trinabean]

I stay out of arguments about 'hybrid vigour' as unfortunately, I have a very sickly pedigree.

No doubt about it some lines and some breeds have some big issues to deal with but this is about selection not in breeding.

It wont be magically fixed for consecutive generations if we just start outcrossing - in fact in may give us more grief than we have now

Absolutely Steve, and I wasn't suggesting outcrossing. I still prefer the predictability of living with purebred dogs.

I more meant that my own dog is, sadly, not a great example to use in arguments about the health of pedigree vs the 'hybrid vigour' of crossbreds. I wish it was different.

Yep I got that was what you were saying but there is a big push on for us to outcross and crossbreed - there is a good argument for that in some breeds but its not something that can just be done with no science if its going to help and still leave us with individual breeds.

Oh, ok, I get where you're coming from now. Thanks. :)

Edited: And thanks Stan's mum.....

Edited April 6, 2013 by trinabean

[Mrs Rusty Bucket]

Inbreeding did not help many of the European royal families.

http://en.wikipedia.org/wiki/Prognathism#History

[angelsun]

The arguement I use is simply this:

No dog is guaranteed to be free of any and all genetic issues that may shorten or cause lack of quality of life. However, with a pedigree dog, you have a great chance of this due to generations of testing and selective breeding with known ancestry.

Hybrid vigor is put forward as a sale tactic. The claim that the 'oodle'/'spaniel' has no health issues, but when questioned as to if they tested said oodle or spaniel and if they know that the aformentioned dogs had any issues in their family tree, we find a changed subject or an abuse mutt breeder.

I know many mutts that lived long happy and vet free lives..but I also know many purebreds that are the same.

[mita]

By the way, widening the gene pool within a breed is considered important in the p/b dog breeding world. Specially so, with rare or less common breeds. As this article shows, modern technology makes this easier.

http://www.thetimes.co.uk/tto/science/genetics/article3728614.ece

In my own breed of interest.... uncommon in Australia, but not rare....a number of the registered breeders import bloodlines from other countries to widen the gene pool. And some are exported, too.

[Dame Aussie]

I have had 5 dogs so far in my life.

Pedigree Boxer - Healthy, robust dog, died at 11 from brain cancer.

2x backyard bred dogs, littermates, Chi x JRT mated with a Maltese mix. One had both patellas done and was PTS due to a brain tumour at 17, other had no health issues throughout her life and was PTS shortly after her brother went, she was deaf, blind and had dementia so quality of life was gone.

Currently I have a Pedigree Aussie and an Anatolian x Maremma rescue. Both healthy dogs, the Anatolian goes to the vet more as he has allergies and eye issues in Spring, the Aussie no issues, touch wood!

IMO we are talking about living animals, nothing can or will be perfect and it comes down to the individual animal.

I like having a PB who has had health tests done etc, but it wouldn't put me off another rescue.

Edited April 6, 2013 by Aussie3

[Steve]

Inbreeding did not help many of the European royal families.

http://en.wikipedia....nathism#History

Yes its a case of Ill show you mine and you can show me yours.

I have 8 kids and my husband came from a completely different country with no common ancestors we could find over 26 generations

and 6 of my kids have been diagnosed with a blood disorder which he happened to have and I happen to carry. Outcrossing didnt help us either.

[mita]

Dr Libbye Miller again. It's about working at reducing risk as far as humanly possible. It's not about 'no risk'. There's no such thing:

The fanciers of the breeds, those you see exhibiting their dogs at Westminster and other dog shows, work very hard to eliminate serious genetic conditions. They screen their breeding stock with every available test. They research pedigrees before breeding into other lines, to check for similar clearances in those animals. They contribute money to research organizations to further the work being done to track down genetic problems. They contribute blood, cell samples, etc. from their own animals to help with DNA and genome studies. They have made great progress so far, and they continue to work hard at it....

Are there unethical breeders? Certainly, there are. Just as in any group of humans, you will find the good and the bad...

If you are looking for a nice family pet from a breeder who will be there for you forever, you need to do due diligence. You won't get that from a pet store. You won't get that from the guy selling dogs out of his pickup truck in the WalMart parking lot...

Yes, it takes a little more time and effort to find someone who really cares and does all the work to breed the healthiest, happiest puppies possible and then stands behind those puppies.

[Christina]

It won't need any explanation soon.

With the regulations & laws looming Australia will find out all about hybrid vigour & the lack of it as there will not be any pure bred dogs with a pedigree to check back on.

There will be lots of mongrels with fancy names according to what they are guessed to look similar to. There will be lots of cross breeds with the potential to carry more genetic problems as each breed brings their own genetic faults into the mix therefore creating potential for more faults, not less.

Oh why bother wasting your breath on this same old subject