All of the Clumber Spaniels that are alive today are theoretically the ‘gene pool’. Each dog has a mixture of 50% of both its dam and sire. Even the dog’s siblings will not have the exact genetic make up of that dog, unless they were an identical twin and started from the same egg. Within a litter you can see this with some chunkier puppies, some more fine boned, some longer in the body, some are taller, some are orange, some are lemon, the list goes on. Pedigree dogs are a ‘closed’ population which means there is no adding to the gene pool, unless different dogs are brought into the breed or mutations occur.
In 2019, just 175 Clumber Spaniels were born (registered) in total in the UK. 175 puppies were produced from 35 litters, with an average litter size of 5 puppies. A gene pool will get smaller as dogs are not used to reproduce or the genes are lost naturally (just not passed down). Some traits are bred away from if they are undesirable, such as aggression.
Dogs with desirable traits in the show ring or in the field, may be used over their siblings, this leads to losing valuable genes from the desirable dog’s siblings. The problem is, some of the genes lost may have contributed to an amazing temperament, a really low hip score, fantastic eyes, genetically clear of certain recessive disorders etc.
A popular sire is a dog that has been used to produce a large number of puppies. They are chosen to sire because they have good characteristics that would be desirable in puppies, whether that be looks, health or working ability. They are chosen by breeders to improve the breed.
There is a fine line between inbreeding and line breeding. Inbreeding leads to a loss in biological fitness and can result in reduced fertility, higher infant mortality rate, shorter life spans and increased likelihood of inherited disorders. It means that a dog that is very inbred is more likely to have a recessive genetic disorder.
If a dog has a very desirable trait, such as a Show Champion, it follows that breeders looking to produce a well conformed show dog will seek a dog such as this to sire a litter from their show dog. The ‘chosen’ sire will have the outward qualities they are looking for – mainly good conformation and a nice coat. This dog may also be carrying less desirable genes that are not showing because they are recessive. A recessive gene is one that does not affect the dog if it only carries one copy of the gene (a carrier) but if the dog carries two copies of the gene, they will become affected by it. Here is more information on Autosomal Recessive Inheritance.
Remembering that there is a 50/50 chance of all genes passing down from parents to off spring, breeder’s really do have a tough job choosing dogs to breed. They may breed a large show type dam and sire and will still have some fine boned puppies – nothing is guaranteed in breeding. The trouble is, whilst they are using traits they can see and knowledge of the dogs used, it is impossible to know what recessive genes both dogs carry and what combinations of genes each individual puppy will carry.
Imagine if the dog that has been used a lot (a popular sire) suddenly had a disc prolapse in his neck and had to be put down. That would be devastating for the owners but imagine if all of the sudden, the first of his offspring started to have lameness, one is diagnosed with Intervertebral Disc Disease (IVDD), another has a similar problem to the sire on a family walk and consequently has to be put down. There appears to be a link, but nothing concrete. It may just be that both the sire and dam, when bred together, produced a genetic combination that left some of the offspring with disc disease.
Hopefully, there would not have been a second mating as those puppies could well have the same issues and this is why repeat matings are not the best thing to happen within a small breed. But if there was a problem with another litter the dog had, with a different dam, with some of the puppies having disc problems, there would be a big question mark over using dogs that had that particular dog in their pedigree. If the dog has produced 80+ puppies, that is a big chunk of genes that are going to be avoided.
It may be that the dog does not have any problems and retires quite happily from the show ring. The trouble is that there are now a lot of this particular dogs genes in the Clumber Spaniel gene pool. Any recessive genes he carries may now be over represented in the breed. Many of the puppies could now be carriers of what was quite an unusual gene. If a recessive gene is carried by more of the population, it is more likely to express itself (dogs become affected as oppose to carriers). Autosomal recessive diseases that affect the Clumber Spaniel include PDP1 and EIC.
The other, more obvious problem is that the offspring from the popular sire are closely related. It will mean that finding a dam and sire that are not closely related will become increasingly difficult. This may lead to further inbreeding, which in turn increases the risk of recessive genes expressing themselves. The size of the genetic gene pool will reduce as the genes from the overused dog will be over represented within the breed.
In 2008 there was a damning documentary aired by the BBC entitled ‘Pedigree Dogs Exposed’. It addressed inbreeding issues within pedigree dogs and in particular breeding for extreme conformations. It had a negative financial effect on Crufts and the Kennel Club joined forces with the Dogs Trust to initiate an independent Inquiry into the breeding of pedigree dogs. Patrick Bateson from the University of Cambridge was approached to lead the enquiry and the report can be found here. The report looked at animal welfare along with genetics and inbreeding in show dogs.
It is included within the report that no dog should have more offspring than 5% of the total number of puppies registered for their breed over a 5-year period. 1,076 puppies were registered from Jan 2015 – Dec 2019. 5% of this total is 54 and so no dogs should sire more than 54 puppies. The Clumber Spaniel Club have recognosed this within their Breed Health Plan.
Clumber Spaniel puppies registered in UK
1076 Puppies over 5 year period
Stud dog owners should restrict the number of times their dog is used for stud. Using a sibling of the dog that has not been used many times would be a better choice. This is because they will carry a slightly different selection of their parent’s genes and therefore, if they are not used, some of these genes could be lost forever. As many different dogs, from different lines, should be used in breeding as possible - but responsibly so. It is also worth noting that if the offspring of a particular stud dog are used excessively, this has the same effect on the breed as the popular sire. Cathryn Mellersh from the Animal Health Trust explains the breeding of dogs that are carriers of recessive diseases here.
Kennel Club - https://www.thekennelclub.org.uk/health/for-breeders/understanding-canine-genetics/the-impact-of-popular-sires/