Applying lessons from cattle breeding to canine genetics
As a dog breeder or owner, you likely choose your breed for its distinctive looks, personality, working ability or because it holds a special place in your heart. Behind the unique traits we love lies generations of dedicated breeding. But this can come at a cost – reduced genetic diversity and rising inherited diseases and health issues in many pedigree dog breeds.
A recent paper by John Cole, published in the Journal of Dairy Science, on managing inbreeding in dairy cattle, highlights concerns and solutions that dog breeders could usefully learn from. While cows and dogs are very different, the population genetics challenges facing both purebred animal populations have strong parallels.
The paper discusses balancing selection for traits like production against managing inbreeding and diversity. For dogs, breeders should balance selection for breed standards and desired traits against preserving genetic health and diversity within the breed.
The genetic diversity dilemma
Like Holstein dairy cattle, most dog breeds were formed from a small founding population. Intensive selection for desired physical and behavioural traits reduced the gene pool further. When relatives are mated, it increases homozygosity – offspring inherit identical gene copies from each parent. This isn’t necessarily bad if those genes are favourable. But it also raises risks of inheriting two copies of deleterious genes which can cause recessive diseases like PRA.
The more limited the gene pool, the more that harmful traits can accumulate across generations. This “inbreeding depression” reduces fitness and ability to thrive. Scientists can calculate how inbred a population is from pedigree records and advanced DNA analyses. Many breeds show high and rising inbreeding over decades.
Beyond inherited diseases, low diversity also jeopardises the ability to adapt and thrive in changing environments. Dogs are exposed to all sorts of environmental factors such as diseases and parasites, so we want resilient breeds with enough genetic variation to cope.
Solutions require rethinking tradition
For many pedigree dog breeders, maintaining breed purity and standards is paramount. But as genetic issues rise, we must reconsider traditional practices if we want breeds to stay healthy into the future.
Breed clubs and Kennel Club registries play a key role in change through education, health-testing requirements, and registration rules. But individual breeders, owners and buyers also shape each breed’s destiny through choices like mate selection.
Balancing priorities
Preserving breed traits, improving performance and maintaining diversity are competing goals. In dairy cattle breeding, virtually all emphasis has been on elevating production. But as inbreeding rises, the associated drop in fitness starts to offset any output gains.
A similar single-minded focus on physical appearance or working ability within strict breed standards has tended to make genetic diversity an afterthought in dogs. But evidence suggests that the health impacts now outweigh the benefits for many breeds. As in cattle, we may reach a tipping point if inbreeding continues unabated.
Breeders should shift priorities to consider both improving prized attributes and maintaining genetic health. It’s no longer enough just to avoid very close matings like father-daughter. We must look at mate choice and breeding goals in a new holistic light and act accordingly.
Tools to turn the tide
- Pedigree analysis – New mate selection algorithms can optimise diversity based on ancestry and help avoid high-risk combinations that some breeders and kennel clubs once favoured. Computing power makes such analysis more accessible. The Kennel Club’s Mate Select and Inbreeding Calculators are useful tools for breeders to use when planning their matings. The use of Estimated Breeding Values for complex conditions such as hip and elbow dysplasia also form part of this toolkit.
- Genetic screening – DNA tests identify carriers of defective genes. These allow informed breeding choices so problems are not multiplied. Breeders can now make decisions that avoid producing affected offspring. Sensible choices to avoid further reductions in genetic diversity include mating carriers to clear dogs. The use of affected dogs, mated to clear dogs is also a viable option in many cases. We should not be throwing the baby out with the bathwater and eliminating dogs from the gene pool simply because they carry a particular genetic mutation, especially when a reliable DNA test is available.
- Outcrossing – Bringing in dogs from another line or breed introduces new variation. While some outcross offspring may not fully meet the breed standard at first, the hybrid vigour and new genes offer big benefits if these dogs then enter breed lines. Such outcrossing programmes must be designed carefully to balance new diversity and preserve desired traits from the original breed. Several such outcrossing programmes are being supported by Kennel Clubs around the world.
- Gene editing – New biotech tools like CRISPR may someday allow correcting genetic disorders without introducing unwanted traits from other breeds. This can remove recessive diseases so they no longer threaten the gene pool. But much more research on effectiveness and ethics is first needed.
Buyers can steer change
If buyers who value health and genetic responsibility selectively purchase from breeders who prioritise these factors in their breeding programmes, it will drive change. Seek recommended and relevant health tests for your breed, and breeders who track and maximise diversity in their lines. Support those who are innovating with new science-based approaches to improve breed genetics. The International Partnership for Dogs’ DNA test “Relevance Ratings” provide an evidence-based way to identify which tests are important and worthwhile for particular breeds.
A shared responsibility
Breed conservation is a team effort between Kennel Clubs setting standards, scientists providing tools and data, and breeders making it happen through their mating selections. Education and public awareness are also key.
By taking a realistic view of the genetic risks facing dogs today and adopting a balanced approach, together we can ensure our pedigree breeds stay healthy and long-lived for generations to come. Let’s not wait until we’re facing the same dire genetic straits as some cattle and other livestock populations. The tools and knowledge are there – we just need the collective will to put them into practice.
Dog-ED: Social Enterprise 