I recently had a long chat with a spaniel enthusiast who argued, quite convincingly, that the only spaniels we need are cockers and springers, and that all the others are a waste of time. Britain has no fewer than seven native breeds of spaniel. We all know the English springer and the cocker but the other five – Welsh springer, field, Sussex, Clumber and Irish water – are rarities with such tiny populations that the Kennel Club classifies them as vulnerable native breeds. To qualify as vulnerable, a breed must have fewer than 300 registrations a year. In 2022, these five minority breeds only produced 651 puppies between the lot of them.

My acquaintance pointed out that the minority spaniels have such small populations and such little genetic variation in their blood that they are all doomed anyway. If we continue breeding from such a small pool of dogs, then their outlook is gloomy, with ever-increasing problems from genetic diseases. He went on to talk about the coefficient of inbreeding (COI) in these breeds and what it meant for their future.

All the minority spaniels have active breed clubs but if you look at their websites you will be hard-pushed to find mention of COI, as it’s not a subject that they are comfortable with. The COI measures the common ancestors of dam and sire, and indicates the probability of how genetically similar they are. There are advantages and disadvantages to being genetically similar. Dogs that are genetically similar produce puppies that look like them. If you breed a cocker with another cocker, the puppies will almost certainly look like cockers.

To get an accurate idea of how inbred a certain dog is, you should go back at least five generations. What you will often find is the name of the same sire or dam appearing on both sides of the pedigree. This isn’t surprising, as there was a time when breeders regularly mated closely related animals, even fathers with daughters, or brothers with sisters, if they had a characteristic that they liked and wanted to fix. It was remarkably effective, as if you mate brother with sister the resulting puppies will almost certainly look just like their parents.

However, there is a serious downside to such close breeding and the Kennel Club has since banned such first-degree relative mating. While line breeding will help establish the good traits, there’s also a danger of it establishing bad ones. In particular, it can cause the rapid build-up of diseased genes in a population. Even if a breed of dog is unaffected by severe genetic disorders, inbreeding is likely to be felt in equally alarming, but possibly less obvious, ways. Examples range from smaller litter sizes to less vigorous or viable puppies. Fertility problems are common, along with weakened immune systems.

Mammals are remarkable creatures, and there are some striking cases of inbred populations that appear to be healthy. For a classic example look no further than Britain’s muntjac population, which has descended from just a handful of animals that made their escape from Woburn a century ago. Neither their fertility nor fecundity have been affected. However, sufficient research has been undertaken with dogs to show that while a low COI doesn’t guarantee a healthy puppy, a high COI is very much a cause for concern.

The Kennel Club’s website helpfully gives the average COI for all registered breeds, and it also includes a COI calculator. Type in a dog’s registered name and the calculator will tell you its COI. If you are looking for a stud dog it’s a highly useful tool. If possible, always choose a stud with a COI lower than the breed average.

I am not alone in believing that the only way of ensuring that the minority breeds have a future is a programme of carefully planned outcrossing. This has been done successfully in Sweden with the Clumber spaniel. A cocker stud dog of suitable colour and conformation was used on a Clumber bitch, successfully introducing a new bloodline. Now, several generations later, the descendants all look like typical Clumbers but they have the benefit of greater genetic diversity.

Some years ago I wrote that it would be sensible to do the same with the Sussex spaniel, the most inbred and endangered of all our native spaniels. It wouldn’t be difficult to find a cocker stud dog that would be a good match for the breed. My suggestion was greeted with horror by a leading member of the Sussex Spaniel Association, who retorted that any such puppies would be mongrels and thus totally unacceptable to any breed enthusiast. It seems that breed purity is far more important than breed survival, though fresh blood was introduced to the Sussex after World War II, when just seven pure dogs remained. If it was considered acceptable to outcross then, why isn’t it today?

I’ve been a spaniel enthusiast all my life. Although I have never owned one of the minority breeds, I’m keen to see them survive and flourish. I have shot over all the spaniel breeds, with some of my most memorable days rough shooting over Clumbers. However, I’m forced to believe that the minority breeds’ greatest supporters can also be their worst enemies. Breeds are man-made creations, they’re not unique species, and if we want them to survive a sensible approach to outcrossing is essential.