In my search for the right puppy I am looking for parents who have been MRI tested. I am running in to a lot of only the sire tested. Why is this and is it normal?
I take on board what Sins and Margaret have had to say. However, unless I am so tired that I have missed mention of it, I think it is virtually worthless to breed a litter when only the sire is favourably scanned because I believe it is an accepted fact that the bitch (dam) contributes 80% of the genetic inheritance to the pups, whereas the sire (dog) only gives the remaining 20%.
On that basis, were I purchasing a puppy, and only one parent could be scanned, it would have to be the mother before I would show any interest in the litter.
Popular Sire Syndrome and Concerns of Genetic Diversity
Jerold S. Bell, DVM
Department of Clinical Sciences, Tufts Cummings School of Veterinary Medicine
North Grafton, MA, USA
There is a tendency for breeders to breed to the male who is the top-winning dog. This can also occur with a popular dog that has OFA excellent hip conformation, or has produced no epileptic offspring in matings to epileptic dams. Regardless of the popularity of the breed, if a large portion are breeding to a single stud dog, (the popular-sire syndrome), the gene pool will drift in that dog's direction and there will be a loss of genetic diversity. Too much breeding to one dog will give the gene pool an extraordinary dose of his genes, and this will include whatever detrimental recessives he may carry, to be uncovered in later generations. This can cause future breed-related genetic disease through what is known as the founder's effect.
Along with the thrill of owning a popular sire, comes your responsibility to the breed. Over time, you will find out what detrimental genes he carries. Hopefully these will cause minor faults, but occasionally they may cause genetic disorders. The true measure of a conscientious breeder is how this knowledge is disseminated to the owners of the next generation.
Purebred dog breeds have closed studbooks. No new genes are available to the breed, except from infrequent mutations that are usually not desirable. Considering a breed as a whole, genes cannot be gained through selective breeding; they can only be lost. This has lead breeders to question whether a pure breed can go though hundreds of years of selective breeding and still maintain its health and viability.
All genes come in pairs: one from the sire and one from the dam. If both genes are of the same type, the gene pair is homozygous. If the two are different, the gene pair is heterozygous. While each dog can have a maximum of two different genes in a pair, many different genes are potentially available to be part of the pair. The greater the number of genes that are available to each pair, the greater the breed diversity. ...
The loss of genes from a breed's gene pool occurs through selection: the use and non-use of offspring. If a popular sire is used extensively, gene frequencies, and the gene pool can shift towards his genes, limiting the breed's genetic diversity.
Breed Clubs tout themselves as guardians of all that is precious in their breeds. Most, if not all, have codes of ethics. But codes of ethics tend to be toothless documents that get dusted off and waved about only when a club is accused of not having addressed an ethical issue.
Codes of ethics ought to have sharp teeth, but this is not enough. Breed clubs should spend a lot more time-and money-educating their members and the public about the hereditary problems in their breeds. And on funding research on those problems.
No single entity will be more aware of what a breed's genetic drawbacks are than a breed club. It is in an excellent position to monitor those which have already been identified and look out for new ones. Someone needs to bring the attention of the veterinary community to specific breed concerns. Who better to do so than the organizations that allegedly exist for the protection and improvement of those breeds?
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Urging people to lie, intimidating them into silence, even threatening them, is not ethical behavior. Not for breeders any more than anyone else. Nor is it ethical to heap scorn and ridicule upon those who exhibit the moral courage to be open about hereditary disease.
Let me add that far more are not scanning at all in the USA and I don't feel that because of this that only one scanned is enough. However, I hope more and more do scan so we know more history.
I am also seeing lots of adds saying the dams are scanned but no mention of the sire just saying to me that they aren't as careful about the sire they are breeding with. ...
... So far of the few I have sent questions to I am not getting full answers. ie when asked the age of parents I am getting some answers to other questions but no answer to that so just moving on. In the end I won't just be taking the fact that they are scanned but will be wanting to see the certificates. ...
Thanks Rod, I am keeping those points in mind. So far of the few I have sent questions to I am not getting full answers. ie when asked the age of parents I am getting some answers to other questions but no answer to that so just moving on. In the end I won't just be taking the fact that they are scanned but will be wanting to see the certificates.
Off to read the article you just posted...
I have no idea what the study giving the 80/20 percent figures is. I got the information a couple of years ago from a friend who went on various KC or KC approved courses for judges. I will try to get more information if she has it.