Popular sires have had an unhealthy level of input into the gene pool of our sporting breeds, which may be damaging. Could outcrossing be the secret to a long and happy life, asks David Tomlinson
Over time the number of dogs are being put down before retirement has been increasing. Is this due to the gene pool from selected studs that perform well in the field? David Tomlinson suggests an alternative plan that could improve your dog’s lifespan.
GOING OUTSIDE THE LINES
All of us, when we take on a new puppy, hope that it is going to have a long and healthy life. My article on why dogs retire highlighted the fact that getting a working dog to retirement age is quite an achievement and requires more than a touch of luck. Of the 665 dogs in the survey, no fewer than 158 were put down before they reached retirement age. The principal cause of premature death was cancer.
Like cancer in humans, it’s almost impossible to work out where it is most likely to strike, though certain breeds are more susceptible to the disease than others, possibly due to faulty genes. There is a particularly high incidence of cancer in certain lines of flatcoat retrievers, for example, and I know many flatcoat owners who have lost dogs prematurely from the disease. Intriguingly, non-pedigree dogs seem to suffer far less from cancer than pedigrees. It would be fascinating to conduct a study of pye-dogs in India, for example, to see if cancer is a cause of premature death. I suspect that it’s not.
Dog pedigrees would be far more valuable documents if the cause of death, and age, was noted for each of the animals listed. Potential puppy buyers could then glance at the document and work out the chances of their dog reaching its teens. My general advice to anyone planning to get a puppy is to make as extensive health checks as possible on the dogs’ parents and grandparents, though this is often difficult.
A modern problem is that successful stud dogs have had far too much input into the gene pool of our sporting breeds. It’s by no means unusual for a popular stud dog to sire 500 or more puppies, with the inevitable result that future generations will share a common ancestor.I would always avoid buying a puppy if the same names appear on both the sire and dam’s side of its pedigree, something that happens all too often.
The Kennel Club has a handy tool on its website allowing you to check the coefficient of inbreeding (COI). The COI is the probability of inheriting two copies of the same allele from an ancestor that occurs on both sides of the pedigree. This sounds complicated, which it is, but put simply it’s not a good thing. We have known for more than a century that breeding related animals leads to losses in vitality and vigour, and that this can result in serious health problems. However, mating related animals (line breeding) produces more consistent, predictable traits in the offspring. Mate brother with sister, for example, and the resulting offspring are much more likely to resemble their parents than if you breed from two totally unrelated dogs. The puppies will also have a COI of 25%.
Experts advise that a COI of less than 5% is best, and that inbreeding levels of 10% will have a detrimental impact on not only the quality of the puppies, but also the breed. You can check the COI of any registered dog at bit.ly/KCcalculator. Simply type the dog’s name into the checker, and you will get an instant result. The breed average for labrador retrievers is 6.6%: finding a stud dog with a lower figure is a challenge. I checked a number of leading field trial champion stud dogs – the lowest COI I found was 6.5%, the highest 15.4%.
It’s even worse with cocker spaniels. The breed average is an unhealthy 10.6%, but I found field trial champion stud dogs advertised with COIs up to 20%, most were around 15% and none that I checked were below the breed average. However, it’s worth noting that the Kennel Club emphasises that the COI is a measure of risk, rather than a direct measure of health. It is possible that two closely related dogs do not have the same autosomal- recessive genes, while two seemingly unrelated dogs do. It adds that the COI is not a guarantee of health, but is a measure of risk, and higher COIs are best avoided.
Sixteen years ago, I did my own minor experiment in outbreeding, mating my working English springer with a showbred English springer from a leading kennel where the owners both showed and worked their dogs. Apart from the fact that both dog and bitch were black and white, they had nothing in common. My bitch produced 10 strong and healthy puppies, though with variation in size. All of the male puppies were big, with the largest comparable to a labrador. The bitches were smaller, but all grew to be at least as big as their dam, if not taller and heavier.
I kept one of the bitches, who as I write this is sleeping in her bed next to my desk. If she makes it, and it looks highly probable that she will, she will be 16 this month. She still enjoys a 40-minute walk every day, has a healthy appetite – she has always loved food – and isn’t on any medication. Interestingly, she has cost me next to nothing in vet’s bills. It would be good to think that her outbreeding is the secret of her health and longevity, but I’ve no doubt that a great deal of luck has been involved, too.