Inbreeding is quite safe

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A fabulous bit of archive from 50 years ago in this week's Dog World... dismissing concerns about inbreeding in response to what the author calls "the sheer volume of uninformed criticism which has lately appeared in the lay Press and been given public utterance by those who should know better than to indulge in such scientifically unsound generalities".

Those who should know better were, in fact, senior vets - not, of course, that they are necessarily experts in genetics. But then neither was Dr E Fitch Daglish.

Daglish's article was in response to the first high-profile challenge in the early 1960s to the way dogs are bred under kennel club rules. This included an article published in The Field on 8th Feburary 1962 and, again, in December 1962, in the Canadian Journal of Comparative Medicine and Veterinary Science. (When A Vet Should Speak Out, Can J Comp Med Vet Sci, 26 (12), 1962). Despite the title, the author chose to remain anonymous - an indicator, perhaps, of the pressure vets felt even then about not alienating their best customers.

The anonymous vet wrote: "Breeding from defective animals not only destroys bloodlines, but discredits a breed both at home and overseas. Unfortunately, this warning sometimes falls on deaf ears. It is a great temptation to the owners of a champion to disregard or deny any defects that are repeated in its offspring. Their natural inclination is to keep quiet about the matter. There is no suggestion that dog breeders and exhibitors are deliberately dishonest. Their worst faults are ignorance and a disinclination to face up to unpleasant facts."

The author went on to refer to an article published in 1961 in the Journal of Small Animal Practice (JSAP) in which Dr S Hodgman stated that the Executive Committee of the British Small Animal Veterinary Association had become 'very concerned' at the serious increase in the number of pedigree dogs suffering from defects and abnormalities.

"Dr Hodgman's central point was that there is strong evidence that many of these conditions are hereditary. The present situation may have arisen because of the ignorance of many dog breeders of elementary genetics. Irrespective of the causes, the alarming fact remains that the percentage of unsound stock is on the increase."

Dr S F Hodgman was a founding member of the BSAVA and a senior research vet at what is now the Animal Health Trust in Newmarket.  Hodgman wrote several articles on the issues at this time, including:

Hodgman S, ‘The duties of veterinary surgeons in attendance at championship dog shows’, Brit Vet J, 117(5), 1961*

Hodgman S, ‘Abnormalities in pedigree dogs: Their surgical correction, related to Kennel Club Rules and Regulations’, J Small Anim Pract, 2 (1-4), 1961*

Hodgman S, ‘Abnormalities of possible hereditary origin in dogs’, Vet Rec, 74(46), 1962*

This third paper, presented to the BVA Congress in September 1962 and picked up by the newspapers of the time, is the chief reason for claims of an "attack" in the above article by Daglish. But in fact, it is clear from the history books that Hodgman worked quite closely with the Kennel Club. His articles are measured and, although critical of some breeders, he was not unsupportive of the KC - maintaining that it was not their job to tell breeders how to breed their dogs.  In fact, the Kennel Club collaborated with a survey - largely prompted by Hodgman -  into inherited problems. 

The following year, in 1963, came this article:

Hodgman S, ‘Abnormalities and defects in pedigree dogs: I, An investigation into the existence of abnormalities in pedigree dogs in the British Isles’, J Small Anim Pract, 4(6) 1963 *

In this, Dr Hodgman wrote: “The preliminary results of an investigation into the existence of certain deleterious conditions that are hereditary are presented. Thirteen conditions found to be of major concern and of these five were considered to be of importance and needing immediate consideration are hip dysplasia, patella luxation, entropion, retinal atrophy, and prolonged soft palate. The second priority group consists of abnormal temperament, skin fold dermatitis, uterine inertia, elbow dysplasia, ectropion, trichiasis, and deafness”. 

That same year, during his opening address to the 6th BSAVA Congress, president Dr Oliver Graham-Jones announced: "We have recently been to the House of Commons on your behalf and met many members of both Houses. We told them of our tremendous interest in the abnormalities of some of the dogs that we are called upon to treat; and explained that our concern is that dogs are being bred and born into this world to suffer throughout their lives from certain conditions which probably could be prevented." 

The issues were also discussed during a symposium at that year's Congress entitled Abnormalities and defects in pedigree dogs and six accompanying papers were published in JSAP - the last one by Hodgman referenced above, plus:

Hein H, ‘Abnormalities and Defects in Pedigree Dogs-II. Hereditary Aspects of Hip Dysplasia’*

Knight G, ‘Abnormalities and Defects in Pedigree Dogs–III. Tibio-Femoral Joint Deformity & Patella Luxation’*

Barnett K, ‘Abnormalities and Defects in Pedigree Dogs–IV. Progressive Retinal Atrophy’*

Willis M, ‘Abnormalities and Defects in Pedigree Dogs—V. Cryptorchidism’*

Frankling E, ‘Abnormalities and Defects in Pedigree Dogs—VI. The Breeders' Point of View'*

In fact, some action did follow. The fuss was directly responsible for the founding of the BVA/KC Hip Scheme (largely thanks to strong lobbying by geneticist Malcolm Willis) and the concern about crypotchordism prompted the Kennel Club to bring in the rule that all dogs must have "two fully descended testicles" - hence why all show judges today fondle them in the ring. 

But the inbreeding message got lost - until, pretty much, Pedigree Dogs Exposed in 2008 - and inbetween there has been almost 50 years of breeding that has led to a loss of genetic diversity that may well prove cataclysmic in some breeds, as is now more generally acknowledged.

Daglish (a naturalist, engraver, dog show judge and author of several books on dogs) writes above: "It has for long been commonplace to ascribe such undesirable traits as loss of size, lack of resistance to disease, infertility or the incident of physical deformities or abnormalities, to say nothing of mental aberrations, the practice of inbreeding; wholly disregarding the fact that if such defects come to light as a result of inbreeding it is the fault, not of inbreeding as such, but of faulty selection of the partners to a mating."

Of course some breeders still maintain this (and there were some very strong editorials in the dog press defending  inbreeding following Pedigree Dogs Exposed). But we now know that they are wrong. Well, mostly.

We now know that inbreeding in and of itself does indeed lead to the very problems Daglish denies above, irrespective of specific, disease-causing deleterious recessives. This is because it leads to not just the fixing of traits that are good and desirable, but homozygosity in other areas of the genome, reducing  fertility, fecundity and our dogs' ability to respond to life's onslaughts. This is why every conservation programme of wild species (and indeed domesticated rare breeds) centres on trying to maintain as much genetic diversity as possible. 

Sameness is the spice of life? Doesn't have quite the same ring to it, does it?

Good selection - particularly that which mimics natural selection in ensuring that only the fittest get to breed - can mitigate these effects for a while. This is why we do see some fit wild populations that are very inbred. It may even prove possible for one or two dog breeds of the many to come out the other side of a lot of inbreeding, having purged all deleterious recessives. But the odds are stacked against it, hence the increasing focus on the importance of maintaining genetic diversity in dog-breeding.

*I'm afraid none of the above-cited articles are freely available online, hence no links - but if you would like to see them, please email me privately.

Many thanks to bulldog historian Stuart Thomson for some of the history above (see here).