Popular Sire Syndrome

I'm going to comment on the “popular sire syndrome” based on what I have read and my understanding as a scientist of population genetics. First, it probably is a good idea to review some of the ideas about animal husbandry.  Historically, in-breeding and close line-breeding was the choice for breeders.  By breeding related individuals , the breeder increased the odds of producing dogs homozygous for the traits desired and would often prove to produce get of similar type. By virture of being homozygous,  individuals were also more likely to produce those traits in the next generation. 

By repeatedly using line breeding, however, one not only got desirable characteristics but also the undesirable ones, that often were recessive.  In essence, then we will likely begin to see similar events happen with the so called “popular sire syndrome”. Let’s assume that a sire has become popular because he does indeed exhibit many positive traits and is dominant for many of them.  He begins to be used by almost everyone over his lifetime.  His get and grand get are also pronounced as good, based on their wins, etc., and so those individuals are line bred. Continuous back-crosses could potentially be made to the point that breeders may not even be aware how closely bred their animals are. 

So what now has happened, is that the frequency of some genes in the breed gene pool have become limited while others, either good or bad, have increased in frequency.  The use of back crosses and line breeding on the popular sire will actually result in further decrease and even extinction of some genes while others will become so established that they are homozygous within the breed.. Thus, the gene pool has drifted in the direction of the popular sire.  Too much breeding to any one dog has now caused the gene pool to be heavily influenced by his genes,  and this will include whatever detrimental recessives he may carry. Some of these traits that are manifested will be positive, but others may actually be quite negative and eventually could be lethal.  Unfortunately, many of the negative traits will be uncovered in later generations.  This can cause future breed-related genetic disease through what is known as the founder’s effect.

I’m not suggesting that dogs that are poor examples should be used or that the popular sire should be avoided but the way to have a diverse gene pool is to introduce some outcrosses that may represent type to type breeding, in addition to occasionally doing some distant line breeding then it is possible to maintain genetic diversity.  Essentially then, it is how the popular sire is used and the use and non-use of offspring that will determine whether genes are lost from the gene pool and diversity lowered.

As has been pointed out, not every popular sire becomes so because of his ability to produce quality offspring.  Some are outstanding and have won major events or are owned by individuals who are well known or who are able to promote their dog well.  Such dogs may prove to be dominant for desirable traits or they may prove to not be good producers once their next generation is produced.  Unfortunately, it usually takes a few years to find this out and by that time, the dog has been bred heavily and some damaging genes may already have “overloaded” the gene pool.

Perhaps we need to think scientifically about the breedings that we do.  I think that we could probably agree that no single dog, no matter how great, should dominate the gene pool.  The level of inbreeding needs to be considered during every mating.  The bitch owner also needs to think seriously about the fact that if everyone breeds to the “popular sire”, then where will you go when it is time to make an outcross? 

I think that breeders should concentrate on selecting toward their ideal of the breed standard (whether AKC or FCI), based on ideal temperament, conformation, and performance, and should select against the significant breed-related health issues.  Also, the attitude toward genetic disease and the “secrecy” factor needs to change.  Breeders need to not be afraid to come forward for fear of ostracism and begin to admit that undesirable recessives do occur.  If genetic disease can become a topic that is open and not a witch hunt, then informed breeding decisions can be made.   By striving to breed healthy, superior examples of the breed and having enough information to make a good choice in a stud, the genetic health of the breed can be maintained.

Elizabeth Wenner©