So I came across an interesting Science News article that summarized a research paper on the effect of inbreeding, body size, and morphology on health in dog breeds.
To cut to the chase, the message was what one would expect. To get certain shapes / looks of dogs, inbreeding had to have occurred in the past to perpetuate that look. Along the way, some undesirable health attributes were passed along as well.
The paper (Bannasch et al, 2021) stated that the average inbreeding based on genetic analysis across 227 breeds was close to 25%, or the equivalent of sharing the same genetic material with a full sibling. "Data from other species, combined with strong breed predispositions to complex diseases like cancer and autoimmune diseases, highlight the relevance of high inbreeding in dogs to their health," said Bannasch.
“One must consider that the majority of dog breeds displayed high levels of inbreeding well above what would be considered safe for either humans or wild animal populations. The effects of inbreeding on overall fitness have been demonstrated experimentally using mice, where an overall reduction in fitness between mice with F = 0.25 compared to F = 0 was determined to be 57%.”
While it is recognized that inbreeding is a problem, looking at pedigrees doesn’t necessarily provide a solution, as the data doesn’t go far enough back. The creation of some breeds was started with such a small pool of dogs, that it might be impossible to avoid inbreeding within the breed what-so-ever.
Outcrossing is being proposed in some breeds.
Another study (Knowler et al 2016) conducted a cross breeding program, using 5 Griffon Bruxellois (GB) with chiari-like malformation (CM) and bred them to a mesaticephalic normal Australian terrier and then backcrossing to produce individuals free of the malformation and regain GB breed characteristics. The goal was achieved. The external phenotypes revealed that by outcrossing breed types and with careful selection of appropriate conformation characteristics in the first generation, it is possible to regain the GB breed standard and reduce the degree of CM.
I tried to find more information on Outcrossing Programs that are taking place internationally. I was able to find the following:
Here, I was able to see that the Irish Kennel Club was allowing this for Irish Red and White Setters, the Norwegian KC was doing this for the Norwegian Lundenhund, and the Dutch KC was allowing this for the Wetterhoun.
The Dutch Kennel Club has implemented a project to enhance nose-to-skull ratio. A ratio of below 0.3 has been associated with various health issues. As such there is a breeding ban (or perhaps a pedigree ban, or a ban on showing… it’s altogether unclear as a non-Dutch reader) on brachycephalic dogs. It is contentious, from what I can read online, but the hope is for healthier dogs. However, does that just narrow the pool of dogs available to breed with? Do we end up with new health issues?
So perhaps the outcrossing strategies do make the most sense? My Borzoi breeder said to me that when you look back into the old, old pedigrees, you might occasionally see something like “Rex” thrown in on a line. She said, the ‘old guys’ knew you had to outcross now and then!
All in all, this blog is just for information and thought. It is interesting to me that many breeders and purebred dog fanatics can be quick to vilify the “Doodle” phenomenon. While I don’t disagree that sometimes innocent owners are being sold on a fallacy that their dog will be guaranteed to be healthier, hypoallergenic, and a ‘purebred, multi-generation doodle’. It doesn’t change that they are dogs, loved by their families and sought out for a reason. Furthermore, it would seem to me that this is exactly how new breeds were created back in the ‘old days’.
So, how do we reconcile with the fact that many purebred dogs are inbred and that various measures are being taken to address the health problems that have ensued from this reality, with the out and out condemnation of the ‘doodle’? I think we have to wrestle with this dichotomy. Somewhere in the middle, lies the place where I choose to ‘sit’.
Think on this for the week!